RPM Test; a tale of three twists, Chapter 2 [Archive] - Page 2

MTWeatherman

04-19-2008, 05:45 PM

I’ve been following this thread with interest...a lot of good information in it. Wasn’t really planning on weighing in on it, because as it initially began, viewed it as an excellent well-documented experiment on Larry’s part. Really felt I had nothing of value to add. Still don't. However, sometimes feel the need to express an opinion even though common sense tells me it would be better to keep my mouth shut. This is one of them:

Have to give Larry a lot of credit for doing this test, the manner in which he performed it, and for taking the time to present that information to us...then taking the time to defend it.

That’s really how science should operate. You have a theory so conduct a test to try to validate that theory. Then subject it to a critical peer review. Usually, that review will involve much criticism if it flies in the fact of currently accepted fact. That’s what happened here. Larry stated the conditions under which he performed the test and his results...and a fine and thorough job he did with it. Problem began when he stated his conclusion of an RPM threshold. I don’t see how any fair minded person can argue with his test...or the fact that for his .30 caliber rifles and bullets, he established a definite relationship between bullet RPM and accuracy...which in turn defined an ideal upper velocity limit based on the twist for those rifles.. Now you can argue why that RPM threshold existed, whether it would apply to other rifles with different lands, different barrel lengths, powders etc. or whether revolutions per distance rather than RPM should be looked at also. However, those remain just interesting distractions (doesn’t mean they aren’t worthy of discussion in their own right). It seems to me that Larry accomplished what he set out to do . If one wishes to truly refute Larry on this issue, you’d have to set up a like experiment, post the results to refute it, and accept your own peer review. Until then, the facts as provided by Larry, back him up.

I can do what I want to with those test results...but can't argue with the facts themselves. I can argue why RPM should have an upper limit for his accuracy, if it would apply to other calibers, if it is a hard and fast rule, what other variables could be involved, etc. However, based on his test and for his conditions, he proved an RPM threshold to me. Seems to me it may be a good “rule of thumb” for a “run of the mill” caster to follow on a .30 caliber. I’m not willing to translate that to other calibers at this time due to the different rotational energies involved ...however, with his data in hand I could use that.30 to establish a theoretical value for them as well by assuming a direct relationship to energy involved. That assumption may or may not be true and require further experimentation...but Larry’s information, whether true or not for other calibers, still offers a starting point. I have no doubts that someone with expertise and time for experimentation could push that .30 caliber envelope up...just the way it works. Where casting is concerned, there are too many variables to make hard and fast rules...just good “rules of thumb” which will work in the vast majority of cases. IMO, unless someone can refute Larry's theory with a documented test providing hard facts, Larry has done just that.

My background is math and physics. I understand physics and mathematics which has appeared here. Physics really comes into play in trying to do an in depth study of this casting and shooting sport of ours. However, it’s so complex in that we also need knowledge of chemistry (primer, powders, lubricants), metallurgy (barrels and bullets), and engineering (bullet and firearm construction) among others to begin to approach a complete scientific look at it. Even then, one would still have a real problem in applying pure science to the issue in that one couldn’t measure initial conditions accurately enough (center of mass of each bullet, energy equivalency of each powder charge, case tension...on and one) , ...or the actual forces and dynamics involved once that trigger is pulled (barrel harmonics, pressure curve, bullet friction, acceleration, associated bullet deformation, etc.) . The list of what we’re guessing or assuming is pretty large. As a result, theoretical implications are open to dispute. All we have is empirical evidence...such as Larry provided.

I am grateful to anyone who is willing to conduct research and provide their results and conclusions. Even if one disagrees with a conclusion, the research remains valuable in and of itself. Review the data, draw your own conclusions if you wish, debate them if you must , but please don't let those honest debates degrade to personal attacks. When it becomes personal, only the “thick skinned” will publish their study or voice an opinion...and we will all become poorer for it.

Kudos to Larry for his work!

runfiverun

04-19-2008, 06:15 PM

MtWeatherman
well said, oh
thats how it starts. now you done it.

for sure there are a couple of good ways to start a DISCUSSION on this board.
rpm's,lube, g'cs, metal mix, and velocity. to name a few.

Tiger

04-19-2008, 07:14 PM

Mtweatherman

You said this: Now you can argue why that RPM threshold existed, whether it would apply to other rifles with different lands, different barrel lengths, powders etc. or whether revolutions per distance rather than RPM should be looked at also.

I don't why you say it existed when nobody has proven that. You touched on something important in my opinion. There are too many different riflings (and imagine all the different groove depths, land heights, the width's of both, the angles of the groove sides, and much more. Larry can only suggest there is a threshold for his particular rifles and I give him the benefit of the doubt that someone who has same rifles might get same results if they are using the same powder lot, primers, brass, and alloy...throw in reloading dies too.

Buckshot does pretty well with his 6.5 Swedes. I think in one of the searches he had some bullets from someone and was testing beyond the 1900 fps when he run out of them. Too bad as I would like to know what the outcome would have been. As I was saying though the Swede can easily shoot accurately from say 1600 to 1900 fps as Buckshot and many others have done. Buckshot obviously shot the Swedes with their iron sights so maybe with a telescopic sight the accuracy may have been much better. If that is so then it would raise the Swedes imaginary rpm threshold. Let's assume the rifling twist is 7.5 in the Swede. That would give a rpm of 153600 to 182400 rpm. That is on the upper edge and the later figure out of Larry imaginary threshold. If there is a threshold for rpm it certainly looks like it is not equal in different calibers not to throw in all the differences that I fore amentioned at tthe beginning of this post.

It's late for me so see you next time

Ralf

Larry Gibson

04-20-2008, 12:03 AM

MTWeatherman

Thanks for the input. As I've said the results of the tests so far indicate there is a RPM threshold. I don't mind the disagreement but as you say those who disagree should run tests and post results that back up their disagreement. They also must be able to defend their test results as I am defending the conduct of my tests and the results. Some still do not understand that I am continuing the test to see if there is anything I may find that refutes the existence of a RPM threshold. At any rate I am conducting the test with .30 caliber because I have the three different twist rifles of the same cartridge. When tests with the .30 caliber bullets are complete I will also run a series of tests with cast bullets in a 6.5 Swede (mine has a scope on it Ralf) using a new milsurp barrel with 7.5” twist that is on a M98 SR Mexican action. It is a very accurate 6.5. Also with the .223 Remington using 7, 9, 12 and 14” twists, on a M95 Chilean 7x57 with an excellent 22” barrel with 9.5” twist, in 2 different 30-06 rifles with 10” twists, on a Mini MKX 7.62x39 with 9.5” twist, on a M91/28 Russian MN 7.62x54R with 9.5” twist, on a very accurate M98 8x57 with 9.5” twist, on a M91 Mauser rebarreled to 35 Remington with a 14” twist and on a M70 .375 H&H with a 12” twist. That should be a fairly comprehensive cross section of calibers with various twists from fast to slow which should give us an answer if the RPM threshold applies to more than just .30 caliber cast bullets shot out of the .308 Winchester cartridge. Should be a challenging experiment but worth while and fun to boot!

Larry Gibson

Bass Ackward

04-21-2008, 01:12 AM

As I've said the results of the tests so far indicate there is a RPM threshold. I don't mind the disagreement but as you say those who disagree should run tests and post results that back up their disagreement. They also must be able to defend their test results as I am defending the conduct of my tests and the results. Some still do not understand that I am continuing the test to see if there is anything I may find that refutes the existence of a RPM threshold. Larry Gibson

Don't waste your time or resources. You are correct. At least partly. You have reaffirmed the centuries old axiom to use the slowest twist rate to stabilize the projectile of interest at the velocity of interest. I believe this to be true. So why was I argumentative? Because it doesn't explain success. If you don't follow pressure, you will be a victim of RPMs.

What 44man does with handguns for accuracy beats a lot of rifle shooters with really good equipment. This is another example of going beyond historical norms. We all know that rifles are more accurate than handguns. We can accept that as long as we leave it as a generality and don't try to quantify it cause 44man showed us it isn't always so. So should we continue to propagate the myth? He does it with wide meplat bullets that we know from history to be impossible. Should we dismiss this in preference to wadcutter history?

Bolt rifles are more accurate than levers too. Except not always.

What I object to with the RPM theory, is putting RPM numbers to this adage. RPM numbers are always true. Except not always as I have proven. Odds are you will fail more often at the shooting sports than you succeed. This is true. More true with cast. This becomes more true as you climb the velocity ladder. But it doesn't mean that jacketed are always more accurate than cast. Or that high velocity with cast is impossible. Just more difficult which is what the RPM theory says to me.

None of these things are spectacular feats. Except that they dispel what we have long accepted. We all want to know why. The RPM theory tells folks that are interested why they failed. Just not how to succed.

leftiye

04-21-2008, 07:58 PM

RPM meets Chicken:

As B.A. says, the RPM barrier varies. What this means is that what we do to get less deformed, less unbalanced boolits results in RPM effects not occurring until a higher velocity with a particular gun/ load/boolit combination. So the barrier varies for caliber,boolit design, booit weight, alloy, particular gun, quality of casting, powder, powder charge, primer,and all of the other variables that we deal with in reloading.

We have all of the variables which affect accuracy as traditional reloading has been done on the one hand and the effects of RPM upon the finished product on the other hand. This is a chicken and egg problem, but this one isn't endlessly circular. We know what came first. The loading/ casting came before the shooting , and internal ballistics and the accompanying damage to the projectile came next, and then came the flight through the air with RPM, and other things happening. To ignore all of the pre occurring factors and damage that occurred and say that RPMs is THE GREAT DESTROYER OF ACCURACY (echoing DEEP voice) is ridiculous. RPM by itself does nothing. If it doesn't have a defect to exploit it has no effect, that continues to be true until centrifugal force tears the boolit apart. Who knows, velocity by that time may be high enough that the boolit only leaves a grey vapor trail anyway. Or else is deformed by friction with the air- would this be an RPM effect? No more than the other deformations are.

It's tantamount to saying that the backstop berm demolishes boolits. How does this happen? Does the hillside rise up, and crush the boolit? The velocity of the boolit in both cases is necessary for the effect to happen. And here again, we know what came first.

As before, all acknowledge that RPMs do have an effect. For me ( and I suspect for some others also) this is "nuf said."

runfiverun

04-21-2008, 09:09 PM

amen
ley's wait for chapter#3

Tiger

04-22-2008, 01:02 PM

Leftiye

You summed it up perfectly in your last post. RPM don't cause the bullet to become bad, it only accentuates a bullet with defects. If Larry had his one 10 twist rifles with a much longer barrel where he could gain the full benefits of a very slow burning powder his accuracy level for it might come out surprising.

Basically looking at jacketed bullets performance in a fast twist tell you what some things that a cast bullet may have problems with in the same twist.

Ralf

Larry Gibson

04-22-2008, 11:13 PM

Ralf

The 10" twist barrel is 24" and 22" is standard for .308 Winchester. If you'd bother to read the test report (Chapter 2) you'd see with RL19 and H4831SC at 100% loading density velocity and RPM were not high enough to make any meaningful comparisons. A longer barrel would not have added that much more velocity as the 27.6" barrel did not show a great increase in velocity either. It might also interest you to know that my Ross M-10 in .303 with 10" twist has a 29.5" barrel. With C312-185 and 314299 cast bullets and appropriate charges of medium burning powder or a case full of slow burning powder that accuracy still goes south within the RPM threshold.

BTW; did I mention the long barreled M1909 Argentine, or the long barrel M91 MNs, or the M98 8x57, or the long barreled M95 7x57 and the long barreled 6.5 M96 Swede? Strange but they all begin to lose accuracy with cast bullets loaded over medium and slow powders in the RPM Threshold also.

So Larry does has 10" twist rifles, and some with faster twists, with longer barrels. Your latest idea is a dog that doesn't hunt. Might want to ask what Larry has before you suggest what may surpirse Larry.

Larry Gibson

joeb33050

04-23-2008, 08:09 AM

The last 3 graphs have some data problems.
The group size vs. pressure graph, 12" twist, has 8 rather than 7 data points.
group size vs pressure, 1st 10" twist group size is ~1.2". The other two graphs show the first group size as 2.4"
group size vs pressure, group size vs velocity both show the 5th group size as ~5.4", group size vs rpm shows the 5th as ~3.8"; hence the "flat" from the 5th to 6th group size is missing.
There are other problems.
We need the numbers to understand what's going on here.
Specifically, we need:
7 group sizes for each of 3 twists = 21 group sizes
21 associated pressures
21 associated velocities
21 associated rpms

looks like
10"
charge grp size pressure velocity rpm

then for 12" and 14"

joe b.

felix

04-23-2008, 09:28 AM

Joe, if rpm is not going to be MEASURED, you won't need it as raw data. ... felix

Larry Gibson

04-23-2008, 10:49 AM

Joe

You are correct in that there are two errors in the graphs. The scale of the first plots was not enough to give a good visual. Thus when I made the change two plots were not put in the correct place. However, If you look at the graphic upward curve of each they are relatively the same and demonstrate the correct curve showing the effects of the increasing RPM on accuracy. I do apologize as I wanted to get those out before I departed on this trip. Remember the graphs are only a graphic representation and not the correct raw data as noted. End results are the same but I will be much more careful with future graphs (the current ones will be corrected) as I have the scale correct.

Larry Gibson

Tiger

04-25-2008, 12:58 PM

Larry,

I have been busy but I am back.

You know nothing of me to make such accusations like have I read your silly test posts. Of course I have read them and not believing your theory is why I am debating with you perhaps.

Here let me give you one more place to read. This time I give the website site so I hear no accusations about that either:

http://www.shootingsoftware.com/barrel.htm

This is one more reason why you can't nail rpm as the culprit.

Well at least you are having fun shooting, otherwise you have wasted much components, not to say time.

Ralf

joeb33050

04-25-2008, 04:29 PM

I read the cite below, and spent a lot of time going over Larry's test results.
There's an enormous amount of theory about barrel vibration and harmonjics, but I've never seen any predictive model or experiment. The "ringing" theory doesn't stand up to analysis; there's always some harmonic and start point that will prove either best or worst.
The amount of testing is not enough to prove anything, however the test data suggests that accuracy falls off at some point in RPM, and as a function of RPM. Accuracy didn't fall off as either pressure or velocity increased.
The ES data doesn't do anything for me.
I would like to see lots of data with the three rifles, at a lower velocity/pressure/RPM and then at a higher velocity/pressure/RPM.
I don't see any other explanation than RPM, from the data. Maybe I'm missing something.
If bullet wobble/precession/tilt/either of Dr. Mann's bullet movements causes the reduction in accuracy, wouldn't we expect BC to drop off also? This is about WHY accuracy diminishes, probably too soon to tlk about this; we need to be sure IF accuracy falls off and where.

Larry,

I have been busy but I am back.

You know nothing of me to make such accusations like have I read your silly test posts. Of course I have read them and not believing your theory is why I am debating with you perhaps.

Here let me give you one more place to read. This time I give the website site so I hear no accusations about that either:

http://www.shootingsoftware.com/barrel.htm

This is one more reason why you can't nail rpm as the culprit.

Well at least you are having fun shooting, otherwise you have wasted much components, not to say time.

Ralf

Tiger

04-25-2008, 05:42 PM

Joe

It may appear it is rpm in Larry's tests. But please do explain to me why there is acceptable accuracy with the famous 6.5 Swede at 1900 fps. That turns up 182400 rpm. That is well out of Larry's threshold. I would expect him to reply that some rifles will do it. Larry mentions else where he has never seen indication of bullet slip in a rifle from the many projectiles he has recovered, although he has in recovered revolver projectiles. I too have collected many fired projectile. In fact if I would have saved them instead of remelting them I would have had quite a sum to supply this forum with plenty of alloy supply. But back to what I was saying. I haven't recovered rifle projectiles that showed any skip like in a revolver perhaps just a very little evidence on the nose when it begins it's journey down the bore. I have recovered rifle projectiles shot from fast twist barrels that did show much pressure where the bullet has force on the one side of groove. These projectiles show a very definate raised edge or ledge whatever you want to call it. Like a fin almost. This is another area in which I disagree with Larry. What amazes me is if the cast projectile is in bore and the pressure side bearing against the groove wall how could it get a raised edge or ledge it has been very expanded to the groove and bore walls? Here is what I think. I think this edge is formed at the very edge of the muzzle where the crown meets it. Then there is no barrel to prevent the edge as the bullet is free from the barrel then. See what I mean? More importantly what does this little fin do to accuracy?

Ralf

felix

04-25-2008, 05:52 PM

leftiye

04-25-2008, 06:09 PM

Joe, The Ballistic coefficient measurement is way too coarse of a thing to take notice of anything except the most very major deformations. Also, as he uses the average B.C., the variations are smaller than they should be. He should find the true B.C. to plot his variations one way only from. This was pointed out to Larry early on. Amazingly, he responded to it. Unamazingly, he then forgot all about it. It does throw his results into question. I suspect that a huge proportion of deformation involves only the very outer skin of the boolit as it travels down the bore. This cannot be seen on recovered boolits after they collide with the earth. This may be demonstrated by the sucess of paper patched boolits in attaining accuracy at velocities where naked boolits fail. Also mentioned. Not allowed, Larry only wanted to deal with naked boolits. No test results, Well that's ample reason to ignore most anything, isn't it?

Ralf, I like your take on what's going on with the raised edges of the grooves in fast twists. Does it also seem that the lead in those places might be less strong and hard than lead is commonly thought to be. Some say that a boolit is not in the barrel long enough to get hot. They also say that it's in flight too briefly to get hot from friction with the air. Ever hear any stories about people picking up a boolit that for some reason is freshly stopped and available to be picked up? They're HOT! Maybe an unfair test, depending on how they are stopped, as bullets that are frangible still penetrate metal - they melt a hole through it (same thing, heat from impact).

Tiger

04-25-2008, 06:14 PM

Keep in mind that expanding pressure seeks the center of the projectile after the projectile starts moving. Hopefully, the pressure escapes equally around the projectile as the projectile base leaves the barrel. ... felix

Felix

We know there is much pressure on the cast projectile enough to make it like a plastic state. So it only has one direction to expand in the bore and that is get longer going towards the front direction. Would you not think that when the bullet arrives at the muzzle and it is still under pressure but as it begins to emerge from the muzzle it now can expand in all directions except back. Maybe we don't realize this because it is much like squeezing caulk out of the nozzle of the caulk tube and it still looks uniform.

So wonder also too if some of the projectiles do have that raised ridge on them but not necessarily every groove on the bullet. How would gas escape past them effect the projectile.

Larry Gibson

04-25-2008, 10:41 PM

Ralf

I'vealso seen those little ridges on the edge of 6.5 cast bullets. All of them were from .264 sized bullets being fired in .266+ barrels. I do in fac know a bit about you, comes from reading your posts. You refer to my answers as silly and yours aren't? Come now, let's try to keep this an intelligent discusion.

There are quite a few discussions regards to harmonics or barrel whip. It does occur. In this cast though, please tell me how rifles that shoot with consistant accuracy using jacketed bullets from very low velocity to very high velocity would all develop barrel whip causing such inaccuracy just by the use of cast bullets? Barrel whip and harmonics do exist but not to the extent we are asuring here. Obviously there is another answer for the inaccuracy.

This test is about if RPM adversely effects regular cast bullets. It is not about PP'dbullets or jacketed bullets. However you continue to mention them and apparently lack the undrstanding that they are not part of this question, ergo they are not relavent.

As to the 6.5 Swede and "acceptable" accuracy at 1900 fps. Acceptable to whom? And just what is "acceptable"? The question is does RPM adversely affect accuracy. If you get 1 moa accuracy at 1500 fps and 3 moa at 1900 fps the 3 moa may be "acceptable" but the fact remains it is still more accurate down in the RPM threshold and something is causing inaccuracy. Surely even you understand that 1 moa is more accurate than 3 moa.

Larry Gibson

joeb33050

04-26-2008, 07:43 AM

Joe

It may appear it is rpm in Larry's tests. But please do explain to me why there is acceptable accuracy with the famous 6.5 Swede at 1900 fps. That turns up 182400 rpm. That is well out of Larry's threshold.
Ralf

Sure, here's the explanation. The surface of a spinning bullet has a speed that is a simple function of caliber, twist and velocity. I call this the "rotational speed".
A 7.5" twist 6.5 mm swede bullet at 1900 fps has the surface moving at 211.7fps, the rotational velocity.
A 10" twist 30 caliber bullet at has these rotational speeds, fps:
10" 12" 14"
2100 203.2 169.3 141.5
2200 212.9 177.4 152.1
2300 222.6 185.5 159.0
2400 232.2 193.5 165.9
2500 241.9 201.6 172.8

The swede shoots well (I'm told) at ~212 fps rotational speed.
Larry's tests shot well until the rotational speed got above ~212 fps, and did very poorly with the 10" twist rifle at 240 fps rotational speed.
So the RPM explanation is maybe a rotational speed explanation, and your question is answered.

For a calculator that makes these numbers easy, see the book at http://sports.groups.yahoo.com/group/CB-BOOK/
in FILES. See the EXCEL workbook "TWIST MV RPM CALIBER ROTATIONAL SPEED"

See?
joe b.

joeb33050

04-26-2008, 07:49 AM

sundog

04-26-2008, 08:07 AM

Too me, for the purpose of testing loads, accecptable accuracy is the point at which, while increase velocity, the smallest group is attained, consistently. If the group is not small enough to meet your needs, move on to other combinations.

I've shot a lot of cast in the Swede - different boolits and powders. My best loads, which won groups, scores, and aggregates in military bolt matches, never exceeded 1650. Anything past that with the combinations I tried shot increasing larger groups. With 140 gr flat base condums, the same rifle shoots best at ~2400.

joeb33050

04-26-2008, 10:04 AM

.
My background is math and physics. I understand physics and mathematics which has appeared here. Physics really comes into play in trying to do an in depth study of this casting and shooting sport of ours.
Kudos to Larry for his work!

I've heard about but can't remember ever seeing a bullet blow up in the air. I've seen "vapor trails" many times, no blow ups.
I've always asumed that a blow up was due to a bit of the outside of the bullet being smurshed off, bullet way out of balance with a smursh out in the air, then a blow up.
Here's what I'd like to know. Will a cast bullet blow up? What does it take to blow up the bullet?
The model I see(example) is a spinning bullet, say .308" dia. Now think of the cylindrical part maybe .025" thick, on the outside of the bullet. The cylindrical part is .308" OD and .258" ID. What does it take to make this cylindrical part leave the core?
Bullet alloys have tensile strengths in the 2000 psi = lead at 4 BHN to 10000 psi lino at 22 BHN.
Specific gravities range from 11.34 lead down to ~9.5 hard alloys.
I've asked several people to help me with the calculations, no response to date.
How about putting that math and physics to work and figuring this out?
Thanks;
joe b.

longbow

04-26-2008, 11:20 AM

joeb33050:

I posted the equation for calculating stresses due to rotational forces here:

http://castboolits.gunloads.com/showthread.php?p=300036&highlight=longbow#post300036

Post #62

I had thought previously that the RPM being developed might cause enough stress in the boolits to make them yield and deform. Not so at the RPM's we were looking anway. I didn't increase RPM's to find out where the rotational stress would exceed the yield strength.

This also assumes pure rotational stress and does not take into account imbalances due to voids, deformation due to uneven obturation, slumping, casting imperfections, misalignment in the bore, etc. which certainly would have an effect but I think if the bullets are well cast and weighed before testing the effects from casting defects at least would be very minimal.

If a bullet "blows up" the implication is that ultimate tensile stress of the the bullet has been exceed substantially and pretty much throughout the bullet material. Otherwise it should simply deform, lose stability and tumble - maybe breaking into a few large pieces.

I have never blown a bullet up myself (don't have anything that shoots that fast) but I believe it happens. There are lots of reports of small bore light jacketed bullets vapourizing just after the muzzle.

Speculation on my part but it is possible that bullet blow ups are at least partially due to the fact that the bullet (and jacket) material are yielding in the bore due to the intense pressure and acceleration. The body of the bullet is contained by the bore so can't expand beyond groove diameter until it clears the muzzle. There is still a significant force on the base of the bullet while the body is leaving the barrel and is unsupported.

Longbow

leftiye

04-26-2008, 12:52 PM

When the accuracy goes south, I'd expect the BC to go south. I do not understand either of your three contentions.
If more testing shows accuracy falling off and BC not, then we need an explanation.
The BC of the 10" twist bullets did not differ much from the 12" and 14", and it should have.
joe b.

Nor do I understand your contentions. Accuracy seems to me to be totally separate from Ballistic Coefficient (unless you have an inherently inaccurate design/shape - and at stabilized RPMs/velocities there are precious few of these). Those boolit designs with poorer B.C.s just slow down faster.

All I said was that B.C. is a poor measure of all but the most drastic boolit deformations. Other things may have as much or more effect on B.C. making this a corrupted test, and the little deformations that affect balance and boolit fit in the bore will not show up in the B.C..

On the other hand, I have read of tests done with deformed boolit noses that said that accuracy was not affected grossly by gross deformations of the nose. Bases on the other hand didn't need much imperfection to destroy accuracy, and a deformed base probly wouldn't affect B.C. much IMO. Actually might be more streamlined, and cause a higher B.C. (if it rounded the corners of the base).

Tiger

04-26-2008, 02:54 PM

Same thing all time with Castboolit forum. The discussion turns too scientific with many mind boggling formulas and so forth.

First I see that one shooters accuracy is not another shooters requirements. Larry will not define accuracy part of his scheme to make his rpm threshold work I think. Come Larry tell us what accuracy is.

I will say one thing this discussion has made me do many searches on the forum and pm some members as total material is not all here. Okay I find out some time ago a previous member who has a mold business had some kind of contest of shooting to some accuracy degree of the bullet doing 200000 rpm or more if he prefer. Seems not too many members participated or maybe not post what they find. But one member did obtain good accuracy with rpm at or maybe little over the 20000 rpm set. So I do the calculations for the bullet rotational speed as JoeB calls it and I find it 244 fps. Joe the rpm he got was 200084.2. The twist of his rifle was 9.5. Divided by 60 to convert to seconds I get 3334.73. The caliber was 7mm so I use .284 figure for circumference so I can get feet per second and I get the figure 297.647 fps Joe. So think that changes your explanation of my question why the 6.5 Swede with faster twist still shoot pretty good accuracy at 1900 fps.

Like I said we need Larry to define his accuracy in terms of inches or decimals.

Ralf

Tiger

04-26-2008, 03:06 PM

joeb33050

04-26-2008, 03:17 PM

I know you did, and I don't understand it.
I need to see some calculations/results that maybe look like this:
12 BHN X 480 = ~6000 psi tensile strength
x axis = velocity
y axis = caliber
graph/lines show where the force = 6000 psi
maybe a line for 7" twist, 8",......?20"

so I could look at the graph and see where the bullet might blow up. Look at caliber and velocity, see twist where blow up.

Maybe this isn't the best display, but it works for me so far.

We've got tensile strength or stress(is that right), velocity, twist and caliber. I/we want to know where the bullet blows up.
Can you do this?
May I put it in the book?
joe b.

joeb33050:

I posted the equation for calculating stresses due to rotational forces here:

http://castboolits.gunloads.com/showthread.php?p=300036&highlight=longbow#post300036

Post #62

I had thought previously that the RPM being developed might cause enough stress in the boolits to make them yield and deform. Not so at the RPM's we were looking anway. I didn't increase RPM's to find out where the rotational stress would exceed the yield strength.

This also assumes pure rotational stress and does not take into account imbalances due to voids, deformation due to uneven obturation, slumping, casting imperfections, misalignment in the bore, etc. which certainly would have an effect but I think if the bullets are well cast and weighed before testing the effects from casting defects at least would be very minimal.

If a bullet "blows up" the implication is that ultimate tensile stress of the the bullet has been exceed substantially and pretty much throughout the bullet material. Otherwise it should simply deform, lose stability and tumble - maybe breaking into a few large pieces.

I have never blown a bullet up myself (don't have anything that shoots that fast) but I believe it happens. There are lots of reports of small bore light jacketed bullets vapourizing just after the muzzle.

Speculation on my part but it is possible that bullet blow ups are at least partially due to the fact that the bullet (and jacket) material are yielding in the bore due to the intense pressure and acceleration. The body of the bullet is contained by the bore so can't expand beyond groove diameter until it clears the muzzle. There is still a significant force on the base of the bullet while the body is leaving the barrel and is unsupported.

Longbow

Larry Gibson

04-26-2008, 03:28 PM

RPM meets Chicken:.....The loading/ casting came before the shooting , and internal ballistics and the accompanying damage to the projectile came next, and then came the flight through the air with RPM, and other things happening. To ignore all of the pre occurring factors and damage that occurred and say that RPMs is THE GREAT DESTROYER OF ACCURACY (echoing DEEP voice) is ridiculous. RPM by itself does nothing.

Well, so far actual testing is demonstrating that RPM is in fact "THE GREAT DESTROYER OF ACCURACY" when the bullet is in flight. The measurement of the BC tells us how well the bullet is flying through the air. A bad unbalanced bullet will not fly as well as a balanced bullet regardless of the nose shape. A deformed bullet will not fly as well either. I am in fact measuring the "real" BC of the bullets.

The BCs of the bullets of all 3 twists were pretty close to the same at various velocities. This tells us that the bullets were suffering the same amount of obturation during acceleration regardless of the twist. Also remember that the BC will also decrease the faster we shoot the bullet (RN and FN bullets). What we find is there is no proportional decrease in the BC to match the decrease in accuracy of the faster twists. This tells us that the faster twist did not cause any more distortion or adverse obturation given the same pressure and velocity as the slower twists. In other words; the thought that the faster pitch of the 10” twist rifling causes more damage to the bullet not pan out.

What we actually see is the 10” twist bullet has the best BC (by a slight margin) at the highest pressure and velocity yet gives the worst (by a large proportional amount) accuracy. The only difference is the RPM. Since we are effectively demonstrating that the bullet of the 10” twist is not more deformed we see the adverse effect RPM has on the bullet. It appears that the RPM is not adverse affecting the stability of the bullet but is adversely affecting the flight of the bullet. Again the RPM threshold is that range of RPM where the centrifugal force of the RPM overcomes the rotational stability of the bullet. I’m beginning to believe the affect is not one of causing the bullet to become unstable and begin tumbling. From the consistent BCs with poor accuracy perhaps when the bullets RPM reaches that point in the threshold the centrifugal force is causing the bullet to follow a more cork screw type flight path. I’m not sure of that at this point but further testing should give us a better idea.

Larry Gibson

Larry Gibson

04-26-2008, 03:30 PM

Ralf

"First I see that one shooters accuracy is not another shooters requirements. Larry will not define accuracy part of his scheme to make his rpm threshold work I think. Come Larry tell us what accuracy is."

Read Chapter 1 & 2. For the purpose of this test it is well defined there.

Larry Gibson

onceabull

04-26-2008, 03:34 PM

Tiger: You do realize that what "Joe "wrote up was done in the era when his rifles shot boolits that kept gaining rpms as they went downrange...with help from his laughing contact in the Sierra ballistics lab...!!! Onceabull

joeb33050

04-26-2008, 03:43 PM

Nor do I understand your contentions. Accuracy seems to me to be totally separate from Ballistic Coefficient (unless you have an inherently inaccurate design/shape - and at stabilized RPMs/velocities there are precious few of these). Those boolit designs with poorer B.C.s just slow down faster.

All I said was that B.C. is a poor measure of all but the most drastic boolit deformations. Other things may have as much or more effect on B.C. making this a corrupted test, and the little deformations that affect balance and boolit fit in the bore will not show up in the B.C..

On the other hand, I have read of tests done with deformed boolit noses that said that accuracy was not affected grossly by gross deformations of the nose. Bases on the other hand didn't need much imperfection to destroy accuracy, and a deformed base probly wouldn't affect B.C. much IMO. Actually might be more streamlined, and cause a higher B.C. (if it rounded the corners of the base).

It seems to me that if s gun is shooting OK, and accuracy falls off as velocity/pressure/rpm increase, that something happened to the bullets. If so, the BC should change. Thus, I would expect BC to CHANGE as RPM etc increase. The 12 and 14" twist guns shot ok till the end. The 10" gun went south. All the business about slump and wobble and so on will change the BC. At least I would expect to see more variation in BC shot to shot, and probably a change in average BC.
Let's try again. Rifle accuracy goes south as velocity rises. One element contends it's about barrel harmonics and vibration. Another contends that it's about bullet deformation/yaw/wobble. (Mann said that inaccuracy was caused by A. wobble, look at the bullet from the rear and see the base rotating about the nose ; and B Yaw, where the bullet, seen from the rear, describes a circular-really screw thread-path.) If inaccuracy is caused by effects on the bullet's shape or path, this will affect BC. N'est ce pas?

If you want to read about some recent results with deformed bullets, go to the book at: http://sports.groups.yahoo.com/group/CB-BOOK/
in FILES
Go to 3.5 DAMAGED BULLETS, and be surprised.

joeb33050

04-26-2008, 03:46 PM

Tiger

04-26-2008, 03:46 PM

Once again Larry: A lot depends on the strength of the alloy and the density consistancy. A friend who worked at BRL (Aberdeen Proving Ground) noted from their testing that over stabilization had little effect on accuracy as long as the bullet didn't distort from the centrifugal forces involved.

Your rpm threshold testing proves nothing. So us some distorted bullets. Read again: over stabilization had little effect on accuracy as long as the bullet didn't distort from the centrifugal forces involved.

I want to see you put in typing in your nest post what your accuracy requirement ARE not what you test says. I want to see for example: One hole all the bullets go into to 1.5 inches. You get the picture.

I believe the man at Aberdeen knows more then what you think you do.

Ralf

Larry Gibson

04-26-2008, 04:19 PM

Ok I get email after the previous post sorry. I proposed Larrys rpm threshold theory to a man that is in ballistics testing. Here is what he had to say.

A lot depends on the strength of the alloy and the density consistancy. A friend who worked at BRL (Aberdeen Proving Ground) noted from their testing that over stabilization had little effect on accuracy as long as the bullet didn't distort from the centrifugal forces involved.

His name is John Shaefer. You know this man too Larry?

Okay Larry now you must prove that there is distortion from the centrifugal forces being done to the inaccurate bullets out of your rpm threshold then maybe you can hold some claim to your theory. We already heard from Longbow on the strength of cast bullets. I read that thread he posted also.

Much for you to think about Larry.

Ralf

Absolutely little for me to think about. It appears you consistantly miscontrue what is said. I do not know John Shaefer but what he says is mostly correct. However is he refering to cast or jacketed bullets? I do not know of any testing at Aberdeen on cast bullets. There is a difference you know. The centrifugal force effect he is referring to is well known with thin jacketed varmint type bullets that do blow apart when spun at high RPM. Also over stabilization does have an adverse effect on accuracy at long range. Those two effects are not what we are testing for. How many times must you be told that?

Larry Gibson

onceabull

04-26-2008, 04:24 PM

Joeb33050: Go to Post titled "calling Buckshot-and others"start date 01-04-06..note particularly post #20,but the whole sorry thing is worthwhile..a lot to be learned about the credibility of some of the anointed ones,not all of whom are mia. Onceabull

MTWeatherman

04-26-2008, 06:11 PM

Joe:
Damn, should have let common sense be my guide and kept my mouth shut. However, an honest question deserves an honest answer and will try to provide one.

Understanding the math and physics prepared by someone else requires far less operating expertise than developing those equations from scratch. Although my background is in math and physics, it will be 39 years this June since I last saw the inside of university classroom (other than an alumni tour). Although physics was required in my profession, computers made that knowledge superfluous rather quickly as I was in the realm of applied atmospheric physics, not research. Suffice to say math and physics is very much the language of science, and like any language, when not used it becomes rusty and in my case is rapidly approaching little more than a red stain. There are much better physicists than I on this board...I’ve seen their work.

With that disclaimer aside, lets consider what is involved from the standpoint of the pure physics involved and any perceived “blowup” associated with a rotating bullet. That rotating bullet contains rotational energy as well as linear energy associated with its forward motion. The amount of that rotational energy is related to it’s mass (weight for our purposes) and rotational speed (directly related to RPM and diameter). For any bullet fired from a firearm with a given twist, once we know the forward velocity of the bullet we can calculate the RPM. From the RPM it’s pretty easy to calculate the velocity of any point on or in the bullet by knowing its distance from its rotational axis. You’ve already done that so well understand the principle.

I believe the implication of rotational velocity needs to be taken one step further. The important consideration here is rotational energy...that’s what we are demanding that the bullet contain if it is not to fly apart. One of the implications of Newton’s First Law is that any object in motion at a certain speed and direction will remain at that same speed and direction unless acted on by an outside force. Any particle of metal on the surface of the bullet or within it wants to continue moving in exactly the same direction it was the millisecond before. That is the force commonly viewed as “centrifugal force”. The force that keeps that bullet from flying apart is the bond that holds the lead together...once exceeded it will in effect “blow up” as each particle takes the tangential path it is currently on...not the continual turning path the rotating bullet is trying to induce on it. Run that rotational energy high enough and any bullet will fly apart...even a solid copper one...just that in the case of the latter is way beyond what is capable of being accomplished in a rifle. As you’ve already indicated, the velocity on the bullets surface, is dependent on caliber. Take a .22 caliber rifle and a .44 caliber rifle (true calibers here, not actual firearm calibers) with the same twist and firing a bullet at the same velocity. Upon firing, both bullets are rotating at the same RPM. From the formula for calculating the circle circumference, we know any particle on the surface of the .44 has to travel twice the distance of the .22. Its speed has doubled...but not its energy. We know from the formula for kinectic energy that if mass remains constant, a doubling of velocity will quadruple the energy since it is determined by the square of the velocity. Every particle on the surface of that .44 bullet has four times as much contained energy as the .22 ... attempting to move it off in a tangential direction to the actual bullet. In effect to attempt to “blow it up”. Also, on the .44, any particle of lead between the radius of the .22 bullet (0.11) and the .44 will have a like increase in energy induced because of that increased velocity. This is the whole principle of the flywheel...to maximize stored energy for any given mass, you want to maximize diameter...most of the energy contained in a rotating flywheel is stored in the outer sections where mass velocity is the highest. The good news is that increase in “gyroscopic” effect with diameter means that you don’t need to rotate a larger bullet as fast to stabilize it. That’s why large caliber rifles can get away with slower twists even while firing relatively long bullets.

I believe that the real issue for on an accuracy threshold may be found to be more directly related to rotational energy of the bullet ...which is dependent on bullet diameter as well as RPM. Run that energy high enough and the bullet will fly apart...at some point below that, depending on how perfect the bullet is, inaccuracy will begin to appear as imbalanced rotational energy adversely affects the bullets flight to the extent it becomes unacceptable. An unbalanced tire remains a good analogy to an imperfect or unbalanced bullet. The less uniform the tire, the bigger the wheel, the faster the rotation and the more adverse the affects on smooth rotation become. An imperfect tire or bullet prefers to rotate around the center of mass and that center is not the dimensional center that the car axle or firearm barrel is forcing upon it. Wheel weights (which we all love)...simply adjust the center of mass toward the center of rotation. We don't balance our bullets...just load and shoot them...weight sorting is as close as we can come to indirectly achieve balance. I suspect that there is a bit of an "average" quality that is produced in a cast bullet...and that's why we have an apparent threshold. This threshold is not linear with twist rate because the associated energies are not linear. In theory, an absolutely perfect bullet should have no upper velocity limit for accuracy...just the disintegration limit when it flies apart. The true energy contained in a rotating bullet would require mathematic integration of the mass and velocities involved. However, for our purposes, I believe a simple calculation of a surface particle energy would suffice. If mass remains the same in each case, then one would simply square the rotational velocity at the surface of the bullet to get it...and use then use this "rotational energy index" to perhaps establish a better upper threshold than pure RPM will provide. Not a hard and fast rule due to differing bullet alloys, degrees of bullet perfection, etc. but likely a useful one nevertheless. Also, other variables become introduced such as a tendency for long thin bullets to bend, etc.

No, I do not have the resources to test that theory myself. I have zero data to try to back it up. As it stands, Larry still has the best substantiated theory out there. It’s why I am extremely grateful to people like Larry who are willing to share their data with us.

So, now we’re back to your actual question, Joe, and the complex world I alluded to in my initial post. As I understand your question, in order to apply science to determine the value at which that cylinder would leave the core, or in effect disintegrate as a lightly constructed .22 condom might do when driven at high speed from a fast twist rifle, one would first need to determine the energy value at which the rotational energy of the lead core is high enough that the lead, without the jacket, would wish to deform (yield strength) and then fail...then one would need to determine the energy or force the yielding and failing lead core would transfer to the jacket that is now holding it all in place, then calculate how much internal force the jacket is able to contain as it itself is under increasing strain from its own increasing rotational energy. However, in order to do that one would have to have an intimate knowledge of metallurgy. Does the tensile strength value of a metal adequately measure its total failure point when the internal rotational energy or force is constantly changing and increasing as one moves outward...and is not a constant force applied externally to the material itself? Do the tensile strength values apply at all in this case? The physics required are complex and beyond me. However, I’m sure it is a problem that metallurgists and engineers have tackled before...and done empirical studies to determine the values. I’ll leave those experts, hopefully someone on this board, to answer it.

No I don’t believe RPM itself is the direct culprit here...I believe it to be an indirect means of measuring the real culprit which is bullet imperfection and our limits in controlling it. However, that may be better measured by rotational energy. Rotational energy better measures our limits by more accurately measuring the stress and accompanying distortion inflicted on the bullet while it is in the barrel and serves to magnify any bullet imperfections, both initially present and barrel induced, once that bullet leaves the muzzle.

However, RPM does provide a good indication of a caliber dependent threshold that the “average caster” can accept as an upper limit for accuracy. It’s a damn good indicator if not the direct cause. Kind of like the health experts telling you that if you’re male you have a reasonable chance of living to be 75 but a poor one of reaching 90. You won’t die of your age...it will be cancer, heart disease, stroke, you name it. Age is a good indicator...not the cause. Same here.

Time to really shut up this time. I’ve said enough to fill 20 average posts.

longbow

04-26-2008, 06:21 PM

joeb33050:

I will do a calculation based on the ultimate tensile stress of the lead to see what RPM's are required for bullet blow up. I won't have time for a day or two.

I will have to go through it a few times to see the differences between bullet diameters. I'll see if I can put a graph or table or something together for you. I am not a math wizard by any means, I am a mechanical technologist with a machine design background I work with stress and strain calculations regularly but not for situations like this so I had to do a bit of digging for the info.

You are welcome to use whatever I come up with in your book but before you do I would like to make sure that it is checked and accurate. No point in spreading misinformation because I made a silly mistake.

Also, as mentioned before, the RPM's I determine are required to produce enough stress in the bullet to cause it to fail and blow up will be due to stresses produced purely by rotation without consideration of imbalances due to voids, surface imperfections, eccentricities, slump, etc.

Anyway, I will do my best.

Longbow

joeb33050

04-26-2008, 06:32 PM

MT;
Is this a "no"? It's certainly long.
I call it "rotational speed" because many identify "velocity" as a vector quantity, and that which the bullet has while twirling ain't a vector quantity. Direction changes instantaneously, non?
Anyhow, Thanks;
joe b.

Joe:
Damn, should have let common sense be my guide and kept my mouth shut. However, an honest question deserves an honest answer and will try to provide one.

Understanding the math and physics prepared by someone else requires far less operating expertise than developing those equations from scratch. Although my background is in math and physics, it will be 39 years this June since I last saw the inside of university classroom (other than an alumni tour). Although physics was required in my profession, computers made that knowledge superfluous rather quickly as I was in the realm of applied atmospheric physics, not research. Suffice to say math and physics is very much the language of science, and like any language, when not used it becomes rusty and in my case is rapidly approaching little more than a red stain. There are much better physicists than I on this board...I’ve seen their work.

With that disclaimer aside, lets consider what is involved from the standpoint of the pure physics involved and any perceived “blowup” associated with a rotating bullet. That rotating bullet contains rotational energy as well as linear energy associated with its forward motion. The amount of that rotational energy is related to it’s mass (weight for our purposes) and rotational speed (directly related to RPM and diameter). For any bullet fired from a firearm with a given twist, once we know the forward velocity of the bullet we can calculate the RPM. From the RPM it’s pretty easy to calculate the velocity of any point on or in the bullet by knowing its distance from its rotational axis. You’ve already done that so well understand the principle.

I believe the implication of rotational velocity needs to be taken one step further. The important consideration here is rotational energy...that’s what we are demanding that the bullet contain if it is not to fly apart. One of the implications of Newton’s First Law is that any object in motion at a certain speed and direction will remain at that same speed and direction unless acted on by an outside force. Any particle of metal on the surface of the bullet or within it wants to continue moving in exactly the same direction it was the millisecond before. That is the force commonly viewed as “centrifugal force”. The force that keeps that bullet from flying apart is the bond that holds the lead together...once exceeded it will in effect “blow up” as each particle takes the tangential path it is currently on...not the continual turning path the rotating bullet is trying to induce on it. Run that rotational energy high enough and any bullet will fly apart...even a solid copper one...just that in the case of the latter is way beyond what is capable of being accomplished in a rifle. As you’ve already indicated, the velocity on the bullets surface, is dependent on caliber. Take a .22 caliber rifle and a .44 caliber rifle (true calibers here, not actual firearm calibers) with the same twist and firing a bullet at the same velocity. Upon firing, both bullets are rotating at the same RPM. From the formula for calculating the circle circumference, we know any particle on the surface of the .44 has to travel twice the distance of the .22. Its speed has doubled...but not its energy. We know from the formula for kinectic energy that if mass remains constant, a doubling of velocity will quadruple the energy since it is determined by the square of the velocity. Every particle on the surface of that .44 bullet has four times as much contained energy as the .22 ... attempting to move it off in a tangential direction to the actual bullet. In effect to attempt to “blow it up”. Also, on the .44, any particle of lead between the radius of the .22 bullet (0.11) and the .44 will have a like increase in energy induced because of that increased velocity. This is the whole principle of the flywheel...to maximize stored energy for any given mass, you want to maximize diameter...most of the energy contained in a rotating flywheel is stored in the outer sections where mass velocity is the highest. The good news is that increase in “gyroscopic” effect with diameter means that you don’t need to rotate a larger bullet as fast to stabilize it. That’s why large caliber rifles can get away with slower twists even while firing relatively long bullets.

I believe that the real issue for on an accuracy threshold may be found to be more directly related to rotational energy of the bullet ...which is dependent on bullet diameter as well as RPM. Run that energy high enough and the bullet will fly apart...at some point below that, depending on how perfect the bullet is, inaccuracy will begin to appear as imbalanced rotational energy adversely affects the bullets flight to the extent it becomes unacceptable. An unbalanced tire remains a good analogy to an imperfect or unbalanced bullet. The less uniform the tire, the bigger the wheel, the faster the rotation and the more adverse the affects on smooth rotation become. An imperfect tire or bullet prefers to rotate around the center of mass and that center is not the dimensional center that the car axle or firearm barrel is forcing upon it. Wheel weights (which we all love)...simply adjust the center of mass toward the center of rotation. We don't balance our bullets...just load and shoot them...weight sorting is as close as we can come to indirectly achieve balance. I suspect that there is a bit of an "average" quality that is produced in a cast bullet...and that's why we have an apparent threshold. This threshold is not linear with twist rate because the associated energies are not linear. In theory, an absolutely perfect bullet should have no upper velocity limit for accuracy...just the disintegration limit when it flies apart. The true energy contained in a rotating bullet would require mathematic integration of the mass and velocities involved. However, for our purposes, I believe a simple calculation of a surface particle energy would suffice. If mass remains the same in each case, then one would simply square the rotational velocity at the surface of the bullet to get it...and use then use this "rotational energy index" to perhaps establish a better upper threshold than pure RPM will provide. Not a hard and fast rule due to differing bullet alloys, degrees of bullet perfection, etc. but likely a useful one nevertheless. Also, other variables become introduced such as a tendency for long thin bullets to bend, etc.

No, I do not have the resources to test that theory myself. I have zero data to try to back it up. As it stands, Larry still has the best substantiated theory out there. It’s why I am extremely grateful to people like Larry who are willing to share their data with us.

So, now we’re back to your actual question, Joe, and the complex world I alluded to in my initial post. As I understand your question, in order to apply science to determine the value at which that cylinder would leave the core, or in effect disintegrate as a lightly constructed .22 condom might do when driven at high speed from a fast twist rifle, one would first need to determine the energy value at which the rotational energy of the lead core is high enough that the lead, without the jacket, would wish to deform (yield strength) and then fail...then one would need to determine the energy or force the yielding and failing lead core would transfer to the jacket that is now holding it all in place, then calculate how much internal force the jacket is able to contain as it itself is under increasing strain from its own increasing rotational energy. However, in order to do that one would have to have an intimate knowledge of metallurgy. Does the tensile strength value of a metal adequately measure its total failure point when the internal rotational energy or force is constantly changing and increasing as one moves outward...and is not a constant force applied externally to the material itself? Do the tensile strength values apply at all in this case? The physics required are complex and beyond me. However, I’m sure it is a problem that metallurgists and engineers have tackled before...and done empirical studies to determine the values. I’ll leave those experts, hopefully someone on this board, to answer it.

No I don’t believe RPM itself is the direct culprit here...I believe it to be an indirect means of measuring the real culprit which is bullet imperfection and our limits in controlling it. However, that may be better measured by rotational energy. Rotational energy better measures our limits by more accurately measuring the stress and accompanying distortion inflicted on the bullet while it is in the barrel and serves to magnify any bullet imperfections, both initially present and barrel induced, once that bullet leaves the muzzle.

However, RPM does provide a good indication of a caliber dependent threshold that the “average caster” can accept as an upper limit for accuracy. It’s a damn good indicator if not the direct cause. Kind of like the health experts telling you that if you’re male you have a reasonable chance of living to be 75 but a poor one of reaching 90. You won’t die of your age...it will be cancer, heart disease, stroke, you name it. Age is a good indicator...not the cause. Same here.

Time to really shut up this time. I’ve said enough to fill 20 average posts.

Tiger

04-26-2008, 06:36 PM

Mtweatherman

A most excellent post. There's your answer Larry, your bullets are not perfect. How can your guarantee that each of your bullets are the same and near perfect as can be? You can't. Larry I get like you, once again read my post: A friend who worked at BRL (Aberdeen Proving Ground) noted from their testing that over stabilization had little effect on accuracy as long as the bullet didn't distort from the centrifugal forces involved.

This includes beside not distorting that the bullet is perfect with no defects that the centrifugal force can act upon. Yes Mr Shaefer was talking about all bullets cast, jacketed, copper, what have you.

Still no accuracy definition from Larry. Just go back and read my tests. Can't just type a post with the figures Larry hey? I make it more easy. You do not even have to define as varmint accuracy, deer accuracy, or African big dangerous game accuracy. Merely a maximum and minimum figure.

I give you this Larry. RPM has something to do with accuracy if the bullet is not perfect. Larry how you explain good accuracy at most any velocity and rifling twist with Zinc bullets? Do they cast more perfect then lead alloys?

More for Larry to think about.

Ralf

MTWeatherman

04-26-2008, 06:55 PM

Joe...had to answer to prove I could handle a short post.

The answer is NO...beyond my abilities. Sorry.

Checked one of my fading memory cells and it reports that since velocity is indeed a vector (speed and direction), as you stated, speed would be the correct term in describing the rotation.

MTWeatherman

04-26-2008, 08:10 PM

After glancing through my previous dissertation, discovered another glaring error. In it I stated:

"In theory, an absolutely perfect bullet should have no upper velocity limit for accuracy...just the disintegration limit when it flies apart."

Wrong! There is another factor determining the upper limit for accuracy, and that is that in a rifled barrel, it is determined by the riflings ability to grip the bullet...and any associated gas cutting that follows slippage on the rifling. An absolute upper limit would be determined where the bullet actually strips the rifling.

Didn't correct the initial post, since didn't want anyone to have to go through the entire text again to find it.

At this rate, my thesis will be rejected if it hasn't been already!

leftiye

04-27-2008, 12:25 AM

Mt weatherman, Great stuff! Even your errors give insight. I have no way of being sure, but one or the other, boolit explosion due to centrifugal force exceeding the tensile strength of the metal , or stripping the rifling ( plastic failure of the lead involving stress on the metal incurred by force against the rifling?) would end it all fer sure. I like your estimation of the reason RPMs apears to be the limit too.

Larry admitted somewhere that perfect boolits offer nothing for RPM to act upon, yet here we still are argueing what has already been admitted by both sides. (As per Sesame Street) Larry can you say "Litany"?

runfiverun

04-27-2008, 01:15 AM

how ya gonna make a perfect cast boolit?
i don't think that even if you cast it and then swaged it, it would be perfect.
nor even close.
and weighing everyone is still not a guarantee, even weighing after every operation.
casting ,sizing, lubing, g/checking.
but this is just a real world test with as good as we can get, [at least as good as larry can do]
probably as good as most or less of us could do.
my god it is probably a good thing the internet wasn't around when
elmer , phil , and the good colonel were doing their tests.
as they would still be debating what they were going to do instead of just doing it
working on it and telling others what happened so that they could try it
and say hunh that does seem to work quite a bit better then what we was doin before!!

Larry Gibson

04-27-2008, 02:49 AM

leftiye

Of course I can say litany. However bullets pulling themselves apart because of centrifugal force have nothing to do with the RPM threshold. You see, some of use have been successful and shooting cast bullets at quite high velocity and RPM without them coming apart. Actually many shoot cast bullets at high velocity/RPM without the bullets showing any real evidence of coming apart. However it is the lousy accuracy at these high velocities and RPM levels that is the concern of my tests. The RPM threshold is merely that range of RPM wherein a cast bullet becomes less accurate than it otherwise should have been. Zinc bullets, PP'd cast bullets, cast bullets of specialized design and jacketed bullets appear not to be affected in this same manner. Those types of bullets are adversly afrfected only not in the same way. Only regular cast bullets seem to be affected. I am attempting to learn why. All the various comparisons with those other types of bullets is not relevant and only detract from an intelligent discussion. While MTWeatherman's discertation is certainly interesting and thought provoking it discusses causes and effects way above the RPM threshold and what causes inaccuracy with in that threshold.

The fact that the BCs remain the same at the same pressure and velocity while the RPM is of considerable difference between the 3 twists gives unequivocal proof that the bullets are not distorting or coming apart while in flight. In my case I am not “admitting” anything; I am instead presenting factual measured results from actual tests. Others are presenting only thoughts, opinions and sometimes some semblance of witchcraft. RPM will adversely affect any imbalance in any type of bullet. The question here is why are regular cast bullets so adversely affected with in a certain range of RPM. Perhaps if some would present intelligent response in lieu of responses like Ralf presents we could get somewhere in understanding the cause of cast bullet inaccuracy above that certain range of RPM. The litany of constant comparison of apples to oranges serves no useful purpose.

Larry Gibson

Bass Ackward

04-27-2008, 09:20 AM

The fact that the BCs remain the same at the same pressure and velocity while the RPM is of considerable difference between the 3 twists gives unequivocal proof that the bullets are not distorting or coming apart while in flight.

Larry,

I don't think this is a true statement. The angle difference of the rifling is like changing the pitch on a propeller. So the slower twist rate would have have a higher BC than than a faster twist.

sundog

04-27-2008, 10:43 AM

I shot high power yesterday for the first time since last September or October. With cast boolits. 200 yards. 730/800-6X. Every 7 I shot was my fault and was called - there were no flyers. I suspect this load is capable of shooting master (751). Why this load? Because it shoots. In this gun.

What does this have to do with the current discussion? Maybe nothing, maybe everything.

I am using fire formed, outside neck turned LCNM 78 cases ('06) and visually inspected 314299 sized to .312 and loaded to barely touch the lands over 32.0/surp 4895. Alloy is AC WW/RS. Loob is FWFL. Estimated vel is 1900. I will shoot this load again next month, but I am going to weight the boolits.

I suspect there are at least a couple of things going on here. First, I am trying to maximize concentricity, b) get a good pressure seal, and lastly find a smooth, consistent pressure (which produces velocity which produces rpms which some of you explain as rotational velocity). I prolly ought to run some of these across the chrono, just for grins.

I'm pretty sure that I am at my velocity (rpm) limit with this load in the this gun. Increased charges yielded groups that began to open up.

So here's my take on all this. RPM (which is velocity which is pressure)(explanation of rotational velocity up above was enlightening) amplifies internal errors induced anytime before the boolit is completely free of any force associated with internal ballistics. If a good boolit wobbles or yaws or tumbles, and it is not induced by an outside force, then where did it come from? Call it an indicator or what ever you want. Apply all the formulas you can come up with to explain it. Given a decent platform (barrel, sights, etc) some loads will shoot and some will not. Those that do will have a 'sweet spot'. That sweet spot will be a combination of minimized errors.

My remarks are directly related to a gas checked cast boolit fired in a rifle. I am just a poor country boy trying to make my way in the world. This is what I know. I also know that there are things that I do not know, because I'm still learning.

Larry Gibson

04-27-2008, 11:22 AM

Larry,

I don't think this is a true statement. The angle difference of the rifling is like changing the pitch on a propeller. So the slower twist rate would have have a higher BC than than a faster twist.

Bass

Sometimes what we "think" just doesn't pan out.

Remember I did not "thinK" up the BCs, I measured them with the M43 by atually firing the bullets. They are what they are calculated from the measured velocity loss of real bullets over the distance of 100 yards. I had expected the 10" twist bullets to show a greater loss of velocity and thus a lessor BC also. However the 10" twist BCs were slightly higher when the velocity was above 2150 fps. The facts are what they are no matter how hard we "think" they are not.

My statement of; "The fact that the BCs remain the same at the same pressure and velocity while the RPM is of considerable difference between the 3 twists gives unequivocal proof that the bullets are not distorting or coming apart while in flight" remains a true observation.

Larry Gibson

Larry Gibson

04-27-2008, 11:36 AM

Sundog

314299 sized pretty much the same as your bullet over 29 gr milsurp 4895 with a dacron filler does 1897 fps out of my 24" M1903 match rifle and shoots 1-1.5 moa. That is right around 136,500 RPM. Your load without the dacron is probably pretty close to the same or maybe a little more. You are probably pushing the top end of the RPM threshold as I am. I have used that bullet at 2100 fps for 600 yard shooting but had to mildly clean the barrel every 10 shots to maintain accuracy of 2 moa. Yours is a good load. Have you tried a dacron filler?

Larry Gibson

405

04-27-2008, 11:41 AM

Tiger

04-27-2008, 12:03 PM

Some of you are finally getting this. Sundog, Bass, Leftiye, 405. I especially like Sundogs and 405s remarks. Here what Sundog say: So here's my take on all this. RPM (which is velocity which is pressure)(explanation of rotational velocity up above was enlightening) amplifies internal errors induced anytime before the boolit is completely free of any force associated with internal ballistics.

And here what 405 say:Since pressure, velocity and RPMs are so interrelated I can't completely wrap my brain around pointing to one as the causative culprit.

These are two very very good remarks and show these two shooters are thinking. Notice also how Sundog say "this is how this particular load shoots out of this particular rifle". Thats very important and observant.

Leftiye sums it up pretty good: Larry admitted somewhere that perfect boolits offer nothing for RPM to act upon, yet here we still are argueing what has already been admitted by both sides.

Larry is stuck on rpm threshold. Larry says: However it is the lousy accuracy at these high velocities and RPM levels that is the concern of my tests. The RPM threshold is merely that range of RPM wherein a cast bullet.

Larry tell that to the ones that have shot cast bullets at high velocities and rpm levels. Ralf is trying to show you that if the bullet isn't real defective, isn't flying apart, isn't damaged in the barrel, and isn't damaged somehow outside the barrel, that high rpm is not going to affect it. Maybe it boils down to that you are upset that you can't achieve it and others can.

Larry still no exact accuracy figures in type. Tell us Larry what are you accuracy requirements. You did say to Sundog: 314299 sized pretty much the same as your bullet over 29 gr milsurp 4895 with a dacron filler does 1897 fps out of my 24" M1903 match rifle and shoots 1-1.5 moa. So is that it Larry? 1-1.5 inches or below? Is that your accuracy requirements?

Ralf

felix

04-27-2008, 12:04 PM

Larry, if they are stripping up front, that would improve the BC. If there is absolutely no stripping at the check, then the rotation will still be right on. ... felix

leftiye

04-27-2008, 01:58 PM

"The fact that the BCs remain the same at the same pressure and velocity while the RPM is of considerable difference between the 3 twists gives unequivocal proof that the bullets are not distorting or coming apart while in flight. In my case I am not “admitting” anything" [Quote: Larry Gibson]

B.A., Beyond the rifling pitch issue Larry's statement is also irrelevant - not unequivocal at all. He's mixing beans and horse dung. That's like Larry's earlier statement that it was a PROVEN FACT that RPMs IS THE GREAT DETROYER OF ACCURACY- actually that's only his opinion. And so long as he won't address what's said to him it will remain that, his opinion too.

I figured he wouldn't wait to finish the test before he claimed validation. It would seem that they (boolits) are not coming apart during flight, but no one said they were. What WAS said was that RPM can have no effect if there isn't a defect in shape or balance (or other) for RPMs to work on. Further, that this would be the case until another factor like boolit disintegration occurred.

B.C. doesn't measure distortion unless it's relatively major. Accuracy could go south way before it showed up in a B.C. change. Remember that .001" deflection at the muzzle moves POI at 100 yds. 1" (with or without B.C change). B.C. remaining the same, or getting better MIGHT (but maybe not) indicate no further distortion beyond what existed at the muzzle. But so what? If boolits were coming apart or deforming during flight due to centrifugal force it would even better prove Larry's position! It doesn't make B.C. measurement capable of removing distortion as a variable, except after departure from the muzzle, and only in gross increments then. It would still not be able to measure what happened in the barrel, and that is the stuff inaccuracy is made of. Those are the imperfections that enable RPMs. Further, THAT is what has been said over and over by many posters previously.

Larry is now "not admitting to anything." It don't matter Larry. Ya can't have it any way ya want it to be to fit what is needed for you to win the argument. Either the deformations/imperfections prior to flight are necessary for the RPMs to act upon, or the boolits MUST then be being deformed in flight. You can't "just deny everything." If the distortion etc. isn't happening during flight, then it must be happening before flight - can't happen afterwards and affect accuracy.

As usual, Larry has merely repeated himself, and not addressed what was said. He over and over wants to imply that we haven't read his study. And over and over he doesn't read our posts, and answers something that wasn't said (also known as distorting what was said). I guess I've well proven myself foolish here, it is a waste of time, and I doubt that any progress is even remotely possible.

leftiye

04-27-2008, 02:32 PM

Bass

Sometimes what we "think" just doesn't pan out.

Remember I did not "thinK" up the BCs, I measured them with the M43 by atually firing the bullets. They are what they are calculated from the measured velocity loss of real bullets over the distance of 100 yards. I had expected the 10" twist bullets to show a greater loss of velocity and thus a lessor BC also. However the 10" twist BCs were slightly higher when the velocity was above 2150 fps. The facts are what they are no matter how hard we "think" they are not.

My statement of; "The fact that the BCs remain the same at the same pressure and velocity while the RPM is of considerable difference between the 3 twists gives unequivocal proof that the bullets are not distorting or coming apart while in flight" remains a true observation.

Larry Gibson

Huh? What's this got to do with what was said? Regurgitate the litany?

Larry Gibson

04-27-2008, 05:53 PM

leftiye and ralf

Post edited; I had a long "litany" of responses to your stupid questions but I shall not answer them. As stated the answers are in the facts of the tests.

However, I shall respond to leftiye in particular. I have not drawn any conclusions regarding the RPM threshold thus I have not "claimed validation" before the test was done. The answer was with regards to BCs and the effect different rifling might have on them. My answer had nothing to do with the RPM threshold. Your stupid assumption was way out in left field as usual.

Leftiye, you also make a lot of claims as to what BCs do and don't do. Might we know just how many tests of BCs you have conducted and what equipment you used in those tests? Oh, excuse me, was that answer "none"! Then what you are saying is that you are again making assumptions based on what? Your own opinions....I am making observations based on actual test results. When you can match that with something intelligent please let us know.

Ok Ralf, here's the accuracy answer from Chapter 1; I will compare the accuracy of each rifle unto itself. In other words each rifle and it’s bullets flight will tell us when that rifles accuracy begins to deteriorate."

Ralf, here is the answer from Chapter 2; "Let’s now take a look at the results on target. After all what we are looking at in conducting this test is the accuracy at higher velocity and why that accuracy goes bad. Graph #4 shows us the group sizes vs pressure. Whoa there! Something is amiss….if the time pressure curves are the same, the acceleration the same and the BCs are the same; then if the groups get larger as we increase velocity shouldn’t the groups get larger by proportionally the same amount? [Note; by “proportional amount” is an amount to compare the accuracy of each twist to each other. The proportional amount of increase is found by dividing the increased group size by the smallest group with each rifle.] However, what we see is that the groups do not get proportionally larger as velocity increases. The inaccuracy of the 10” twist increases 5.38 while the inaccuracy of the 12” twist increases 3.14 and 14” twist increases 2.08."

Now in case you haven't noticed there are lots of "accuracy figures there in type". However if in your inability to comprehend that (some might use the word ignorance or even stupidity but I won't. I'll just say you have an inability to comprehend, comprehend?) let me try it this way. Bass sent me quite a few of his 154 gr LBT bullets to test. I ran several tests with several powders including his recommended loads. Out of my 24" barreled '06 with a 10" twist. Shooting 5 shot groups at 100 yards I got 1.1" groups at 1838 fps (132,300 RPM) and using Bass's favorite load at 2493 fps (179,500 RPM) the group was 3.45". The 1.1" group was the best accuracy obtained with that bullet. All groups above that 1838 fps load were larger. Now, some might say that 3.45" is "acceptable" accuracy but that is not the point. The point is that Bass's LBT bullet was more accurate down in the RPM threshold than above it. So the question is; what is causing the bullet to be less accurate? Comprehend?

Another way to look at it is (I'll explain it here since you appparently can't comprehend the difficult aspects of reading and understanding a graph); the 10" twist barrel in the test produced groups of 2.3", 1.9" and 1.95" with 26, 28 and 30 gr of 4895. The corresponding velocities were; 1745 fps, 1894 fps and 2030 fps. The corresponding RPM were; 125,700, 136,400 and 146,200. That gives a fair indication that that particular bullet with that particular range of 4895 is a 2 moa rilfe/load, comprehend? Now, that same bullet with 38 gr of 4895 gives 2491 fps at 179,400 RPM with a 7" group size. Thus we see (perhaps all of us except you and leftiye) that the 2moa is more accurate than 7 moa. That's not to hard for you to understand is it?

Larry Gibson

joeb33050

04-27-2008, 06:16 PM

I've been working on this most of the day, and have an EXCEL workbook to calculate centripetal force. It appears that lead bullets will not blow up with any known velocity,twist,caliber combination.
See http://hyperphysics.phy-astr.gsu.edu/HBASE/cf.html#cfc
for another calculator.
I eagerly wait your results.
Thanks;
joe b.

joeb33050:

I will do a calculation based on the ultimate tensile stress of the lead to see what RPM's are required for bullet blow up. I won't have time for a day or two.

I will have to go through it a few times to see the differences between bullet diameters. I'll see if I can put a graph or table or something together for you. I am not a math wizard by any means, I am a mechanical technologist with a machine design background I work with stress and strain calculations regularly but not for situations like this so I had to do a bit of digging for the info.

You are welcome to use whatever I come up with in your book but before you do I would like to make sure that it is checked and accurate. No point in spreading misinformation because I made a silly mistake.

Also, as mentioned before, the RPM's I determine are required to produce enough stress in the bullet to cause it to fail and blow up will be due to stresses produced purely by rotation without consideration of imbalances due to voids, surface imperfections, eccentricities, slump, etc.

Anyway, I will do my best.

Longbow

joeb33050

04-27-2008, 06:22 PM

Seems almost impossible to cipher all the posts in this thread:(

Looking at the original data.... appears very difficult to name or conclude a simple, underlying "cause" for inaccuracy.
Since pressure, velocity and RPMs are so interrelated I can't completely wrap my brain around pointing to one as the causative culprit. I have a fairly strong background in physics and math.... this one is tough!

And, wonder why Molly has been silent on the debate:confused:.... should be right down his alley given the extensive calling out in his thread... "What makes you think so?"

The last three graphs show that accuracy does not decrase with pressure or velocity, but does decrease = bigger groups with increased RPM.
That's pretty clear to me.
The numbers are too small to decide anything, but the suggestion, from the data, is pretty clear.
More numbers are needed.
joe b.

joeb33050

04-27-2008, 06:25 PM

Larry,

I don't think this is a true statement. The angle difference of the rifling is like changing the pitch on a propeller. So the slower twist rate would have have a higher BC than than a faster twist.

What does this mean? Bullets shot from a slower twist barrel have higher BC than same bullet shot from faster twist barrel? Is that it? Do you have any data, or a cite? Or am I not understanding?
joe b.

sundog

04-27-2008, 06:37 PM

leftiye

04-27-2008, 07:42 PM

Larry Gibson

04-27-2008, 08:49 PM

I've been playing electrician all day. Turned back on, and didn't burn the house or barn down. Big plus! (Yet.)

Larry my match yesterday was not an O3 but a Win 70 heavy bbl that is proven at 600 with SIE match bullets at 600 by previous owner. Ten twist. It dawned on me just now that if my accuracy slides off as summer warms up, it might be charge (pressure which is velocity, which is rpm). My loads did not have any wad or filler.

Sundog

I try real hard NOT to play electrician.....were it me the house would have gone up in flames! The summer heat just might push your load over the edge. Would be something to watch for and interesting to see if it does. However a match is not the time to lose points just to see. Might drop back a gr or two and try the dacron filler. Sounds like a nice old match rifle to me. You shootin' scope or iron?

Larry Gibson

Larry Gibson

04-27-2008, 09:15 PM

Larry, Why don't you just deal with the "Stoopud" issues. Is what is being said right or wrong and WHY. Not your litany about how you see things, nor what you want to deal with. People criticize your concepts and say why, you turn on the record and play them the music.

Quite frankly I'm tired of your obnoxious attitude. You ask a reasonable question even if it is in disagreement with me and I'll answer. I answer with facts based on the tests results or other tests. I do not quote others opinions or theories. If you don't like or agree with what I say then at least come back with some test data or factual information. Your next statement is a good example of your obnoxious attitude.

If you don't like what I said about Ballistic Coefficient, then PROVE ME WRONG! Nothing else will get it! If you don't like the implications that saying that Ballistic Coefficients are flatly inadequate to measuring deformations before the boolit leaves the barrel (that's not even possible BTW), and has glaring reasons that it won't measure problems AFTER leaving the barrel until they're WAY PAST being extreme enough to destroy accuracy. PROVE MY STATEMENT to be wrong.

I presented the test data eveidence pertaining to the BCs. I also made the observations concerning them. The test data has been presented and it proves you wrong. Therefore it is up to you to prove yourself right. Present test data of your own if you'd like.

Otherwise you're not dealing with the issues. Don't tell me you don't think I know what I'm talking about, or that it's speculation, don't speculate yourself about where I got my info, or wonder if it was only my opinion, or ask how many B.C. tests I've done, or call it "stoopud". Address the issue! I'd have stopped long ago if I were as unintelligent as you claim, I'm intelligent enough to notice things like that! Insulting people doesn't get the cows fed.

I did address the issue and if you ask a question it opens it up for me to tell you what I want. If you don't like it then debate the issue with facts. Otherwise obnoxious demands will not get you answers.

So far, I believe you've done this to just about everything I've posted.

Perhaps you should consider the content of your posts, there in you'll find the answer as to why. Bass and numerous others disagree quite a bit and we have a reasonable intelligent discussion. Perhaps the same would happen with you if you were reasonable and intelligent.

And - Oh Yes! You have on the previous page in post 289 said that so far the testing was demonstrating that RPMs is THE GREAT DESTROYER OF ACCURACY in response to my comment that such a conclusion was ridiculous. You've said it other places too.

You might want to read that again. I did in fact state the testing was demonstrating.....etc. Stating that something is demonstrating something is not saying I have "concluded" anything. If I said n airplane accellerating to take off "looked like it wanted to fly" is not a conclusion that it will fly. Perhaps that just flew over your head as most everything else seems to.

Larry Gibson

leftiye

04-27-2008, 10:38 PM

Gawd! He done it again. Where do you deal with the issues? Didn't I say demonsrating? Didn't you quote me quoting you saying it? Duh.

Larry, since you apparently only want to tell me about how you done this, and how you done that and won't on pain of death deal with concepts presented to you that call your "experiement" into question, I'm done. If all you want to do is hold court, and outlaw all who don't adulate you, I quit. What a bunch of b@n*4578. I suspect that this is quite pleasing to you (but why waste my time). Obnoxious my @$$. (You seem to have lost the part about you being insulting, Mr Superior).

sundog

04-28-2008, 10:23 AM

Larry, Redfield Olympic rear with a Gehman apperture, and Palma front. Got plenty of slide left on the rear sight, so even if I slow the boolit down a tad, I'm still good to go for elevation.

If I get some time before the next match, I'll try some loads with 1 and 2 less grains and a dacron wad just to see what they'll do. If I do, I'll post the results.

The biggest problem at the range I shoot at is the hundred yard skipper berm we shoot over. Can you spell M-I-R-A-G-E???

I've also got scope blocks mounted, and a mil dot scope dedicated to it -- just in case...

Larry Gibson

04-28-2008, 12:26 PM

Sundog

That's a good setup.

I use a Palma rear with Gehmanaperture and Palma front on my M70 match rifle .308W. It is the 12" twist rifle used in the test but it also is set up for a scope and has one on it for the test. I also use a Palma rear and Tiger front on my Savage Competition .223. The Redfield Olimpics and Palma's are supposed to be "old" generation sights but I like them. On the M1903 Type II National Match rifle I built I have a Lyman 48 with long slide and 1/4 moa adjustments with a Merit aperture along with a Lyman aperture front. My eyes are still good enough to use iron if the sight radius is long enough and I can adjust the aperture.

They are really fun to shoot a longer range match with. We have the same problem when shooting a 200 yard reduced course at my local range. The mirage coming off the 100 yard berm and grass right behind it can be fierce. Many find it hard to believe that mirage can cause sighting errors with irons sights. But I've had it whip my butt if I didn't pay attention to it enough times to know better!

Larry Gibson

sundog

04-28-2008, 12:45 PM

Larry, I also set up a RI 03 w/HS bbl in a Carbolite sporter stock (VERY comfortable) with Ly 48 rear and Ly aperture up front. Great rifle, and lots of fun, BUT I have not been able to locate a long slide for the rear sight. Do you know where one is at? Long slide, that is. Can't get to 200 very well with heavy cast.

Yeah, those Redfields might be 'old school', but they sure work good.

felix

04-28-2008, 01:13 PM

The only reason the BR crowd likes these high powered scopes is to see the soup. 20X for years has been the norm, until those folks with incrementally more power shot better consistently. There is inclination by some folks to get away from the internal adjusting scopes, and revert back to the adjustments on the mounts. That would be taking care of the repeatability problem of the internals. Repeatability here means better than 1/32 inch or less error per click. Other shooters still use the KY windage and could care less about the click error. There is no correlation that I can muster between the shooters using one system over the other, except for the scope power. ... felix

Larry Gibson

04-28-2008, 01:35 PM

Larry, I also set up a RI 03 w/HS bbl in a Carbolite sporter stock (VERY comfortable) with Ly 48 rear and Ly aperture up front. Great rifle, and lots of fun, BUT I have not been able to locate a long slide for the rear sight. Do you know where one is at? Long slide, that is. Can't get to 200 very well with heavy cast.

I have the 1/2 moa one. Below are pictures, if you are interested PM me.

Larry Gibson

Larry Gibson

04-28-2008, 01:42 PM

Felix

I've used a 25X Kowa spotting scope for years to read mirage. It works well for that. While I shoot a lot of bench rest testing loads the highest power rifle scopes I use are 24X. I understand the need for high power when looking for the nth degree of accuracy but most of my rifles see field duty so the really high powered scopes don't work well there. I seldom measure my groups any smaller than hundreths of an inch anyways. Were I seriously competing in BR I would go to the higher powers.

Larry Gibson

Tiger

04-28-2008, 02:34 PM

Larry

I hope you are not tired of my attitude so we can still continue to argue.

I see you are not going to commit to just typing down your accuracy requirements. I assume from your test then that with optical sights that it is to be 1.5 inches to as small as possible hole. Hey Larry that is my requirement too. For iron sight it is bigger. I don't like to see groups bigger then 2.5 to 3 inch maximum. With receiver sights just little smaller.

I had laugh when you say to Sundog you try not to play electrician. I think you should not play ballistics expert either. How is that for attitude? [smilie=s:

Larry I have done this. Shoot high velocity high rpm with accuracy. It is not easy especially for the new cast shooter. Very much has to be pay
attention to every detail. It is not over stabilization, not the rpm that makes accuracy go bad for some shooters. We know too that breaking the sound barrier has to do with accuracy to some degree. The alloy used for cast bullets like mentioned before is strong enough for much higher pressure and velocity. One time I load up some very high pressure loads for a 7x57 Mauser with very soft alloy to see if I could strip the bullet in the rifling. I could not. I did not get my acceptable accuracy but I tell you that it was good enough for deer accuracy. I was surprise that the bore did not get so much leading. I have never recovered a rifle bullet that showed big stripping.

Everyone keep saying with higher pressure and velocity there is higher rpm. Well back to the automobile tire. One could say the faster the automobile goes the higher the rpm the tires rotate. Well of course. These things are connected and you can not change them. Except if you take a rifle with a very fast rifling twist you can equal the rpm of another rifle with a slower rifling twist that shoots a higher velocity. I can not see how you could make tire rotation change on the automobile going at similar speeds except to have much different size tires.

I believe the whole answer to the accuracy lies inside the barrel and with the manufacture of the bullet and in the assembly of the load and cartridge. Some of the things that jacketed bench rest shooters work on are perfect jacketed bullets and good as possible barrel. There is much more of course but I mention bullet and barrel specifically.

Ralf

Larry Gibson

04-28-2008, 05:16 PM

[QUOTE=Tiger;330467]Larry

I hope you are not tired of my attitude so we can still continue to argue.

Ralf, well at least most of your arguments have some merit. They may be out in left field or not applicable to what we are testing here but you at least present them with some intelligent thought.

I see you are not going to commit to just typing down your accuracy requirements. I assume from your test then that with optical sights that it is to be 1.5 inches to as small as possible hole. Hey Larry that is my requirement too. For iron sight it is bigger. I don't like to see groups bigger then 2.5 to 3 inch maximum. With receiver sights just little smaller.

As I've stated numerous times before I'm not seeking the most accurate loads with these tests. The accuracy is used as a comparative measure. Thus the most accurate load is not applicable to this test.

As to my own accuracy requirements; I seek the most accurate loads for a given rifle for a given application. My accuracy requirements for my M70 target rifle are much more stringent than for my M94 30-30. The accuracy loads for a 50 yard small game load are different than for a deer hunting load. Sometimes I end up with a lot of bullets and just load them to a certain velocity and accept what I get. I expect more accuracy out of a varmiint load in my .22 Hornet than I do with a 500 gr bullet out of my 45-400-70 for use on elk. So in reality my accuracy requirements are the same as yours; it depends. However, once again let me remind you that we do not need to seek the most accurate loads with these rifle to determine if RPM adversely affects the accuracy. The accuarcy requirement is comparative.

I had laugh when you say to Sundog you try not to play electrician. I think you should not play ballistics expert either. How is that for attitude? [smilie=s:

Obnoxious, as usual.

Larry I have done this. Shoot high velocity high rpm with accuracy. It is not easy especially for the new cast shooter. Very much has to be pay
attention to every detail. It is not over stabilization, not the rpm that makes accuracy go bad for some shooters. We know too that breaking the sound barrier has to do with accuracy to some degree. The alloy used for cast bullets like mentioned before is strong enough for much higher pressure and velocity. One time I load up some very high pressure loads for a 7x57 Mauser with very soft alloy to see if I could strip the bullet in the rifling. I could not. I did not get my acceptable accuracy but I tell you that it was good enough for deer accuracy. I was surprise that the bore did not get so much leading. I have never recovered a rifle bullet that showed big stripping.

If you read what I am saying then you'll know that "good enough for deer hunting" is ok but it has nothing to do with the question here. How many times have I said I get acceptable accuracy at HV? And how many times must I point out that "acceptable accuracy" at HV if not better than down in or below the RPM threshold is part of the question we are trying to answer. How many times must I say that it is possible to shoot cast bullets at HV just not with regular cast bullets? When you understand the question then you will quit with these arcane and obnoxious comments and perhaps can be of some use in this quest. You don't have to agree with the results but unless you can come up with actual test data to refute the actual test dat presented then you are wasting both our time.

Everyone keep saying with higher pressure and velocity there is higher rpm. Well back to the automobile tire. One could say the faster the automobile goes the higher the rpm the tires rotate. Well of course. These things are connected and you can not change them. Except if you take a rifle with a very fast rifling twist you can equal the rpm of another rifle with a slower rifling twist that shoots a higher velocity. I can not see how you could make tire rotation change on the automobile going at similar speeds except to have much different size tires.

Changing the twist rate is synonimous with changing the size of the tire. Both will change the RPM given the same speed.

I believe the whole answer to the accuracy lies inside the barrel and with the manufacture of the bullet and in the assembly of the load and cartridge. Some of the things that jacketed bench rest shooters work on are perfect jacketed bullets and good as possible barrel. There is much more of course but I mention bullet and barrel specifically.

You are correct and we have agreed on this numerous times. The quality of the bullet is important and what happens to it inside the barrel is also important. That doesn't explain why regular cast bullets shoot quite well up to a certain point and then accuracy goes bad very quickly. If it were just what happens in the barrel we would see a steady decrease in accuracy as velocity/RPM is increased. We do not see that. We almost invariably see good accuracy until the RPM is within the RPM threshold and then accuracy goes bad. The question is; why?

There is indication baced on measured BCs that the difference in proportional accuracy loss between the barrels is not due to increased inbalance in the faster twist bullets. Contrary to lefiyes position there is a measureable difference in BCs. If we go back to the M118 ammo test I did earlier where I unbalanced the bullets by drilling a hole in the side we find a very measureable differeance in BCs between the balanced and unbalanced bullets. Also we find a measureable difference in BCs of that same M118 ammuniton when fired in the 3 different twists. The higher the measured BC the better the accuracy. The unaltered M118 bullets averaged a BC of .481 for 10 shots. The unbalanced M118 bullets averaged a BC og .473 for 10 shots. The difference in group size at 100 yards was 1.94" and 5.5". The difference in BC is noticeable and measureable even though leftiye doesn't think so.

Now how does this correlate to cast bullets and the RPM threshold? What we find is that even though accuracy deteriorates at a greater disparity with the quicker twists as we increase RPM above the RPM threshold the BCs decrease in a slight predictable amount at an equal rate. Were the quicker twist causing more bullet damage the BC would be lower. It is not and in fact the 10" twist had the highest BC at the highest velocity and RPM. It is thus that I am beginning to think that since the bullets are apparently equally stable regardless of the RPM that the centrifugal force is over coming the rotational stablility and the bullets flight becomes more of a cork screw pattern.

Larry Gibson

leftiye

04-28-2008, 06:42 PM

I'll break my silence only for this. You won't comment on stuff like that unless you think I'm not going to post? That is (even if I was misrepresented) the most attention you've given anything I've said so far. I posted about ballistic coefficient on the very first page of this thread.

As usual, I didn't even think of saying what you are attributing to me, so your criticism of it is irrelevant, also as usual. (must have a cognitive problem with language) Like I said it is surprising that you won't address what has been said to you when I'm around. Please refrain from taking unfair advantage in the present situation.

Bass Ackward

04-28-2008, 10:20 PM

The 1.1" group was the best accuracy obtained with that bullet. All groups above that 1838 fps load were larger. Now, some might say that 3.45" is "acceptable" accuracy but that is not the point. The point is that Bass's LBT bullet was more accurate down in the RPM threshold than above it. So the question is; what is causing the bullet to be less accurate? Comprehend?

Larry Gibson

I think this is the wrong approach and I am going to come at this from a different angle.

Let's reverse the thought process and define slow problems first.

Take a wadcutter out of a handgun. Poor BC. Even though RPM loss is minimal, a perfectly stabilized wadcutter destabilizes and becomes in accurate fairly quickly. Why? Can't be RPMs making it go wild. Must be air resistance. So the answer is to increase RPM with a faster twist rate to compensate for stabilization. Cause if you try to drive the wadcutter faster, it will lose accuracy at the same RPM that a faster twist would stabilize it at a lower velocity.

Take that wadcutter and put a nose on it. Now it's called a semi wadcutter. This improves BC and bullet balance by making it easier to stabilize with weight shifted to the rear of center. But not necessarily making it more accurate at close range distances. Just easier to drive faster. Load that with a low power charge and it too will lose stability at fairly short distance, probably at a longer range than the wadcutter. RPMs remain constant there too, over this short distance but air (wind) really causes the inaccuracy. Shoot 7 grains of Green Dot in a 44 Mag with a 250 Keith in several guns with the same exact twist rate and all will have the load go wild at different distances even though RPMs and velocity are fairly close to the same level.

Same as some 38 twist rifles that can launch 300 grain bullets well and others that can't at the same velocity level, the same (low) RPM level. Can't be too low or no guns would perform well. The typical velocity range for these handgun loads (above) that air affected them, are less than 1000 fps. This equates to 788 MPH. Now when accuracy is lost, these results are fairly understood. Over RPMs are not involved in the inaccuracy. The slugs became destabilized even though RPMs were constant causing air to have more effect. Increasing the velocity of poor BC slugs makes it more difficult to obtain accuracy when it is easier to simply spin it faster with a faster twist if stabilization is necessary.

But change to rifles .... and we lose our common sense when velocity really increases. Air goes from having a major effect on accuracy on a poor BC at low velocity to having ZERO effect what so ever when we double or tripple veliocity.

Load and pressure means nothing to launch at these levels when we KNOW it does in really low levels of both RPMS and pressure. The fact that LArry shoots my bullets differently in his guns is the fault of RPMs and not the mechanical difference in the guns that we readily understand at low levels. Our ignorance cause us to look for excuses.

Is there a sweet spot for for RPMS? Same question can be asked is there a sweet spot for velocity? And what happens if we increase wind resistance by increasing bullet diameter? We lower the ideal RPM or velocity level. Which means we lower the accurate velocity level. Even though 22s are the hardest to mold well, (balance) they have the highest velocity potential. An inaccurate 22 caliber (jacketed or cast) is most often more accurate than a 30 caliber at the same RPM level. Why? Has to be less wind resistance, cause it is just as highly a destabilized slug or worse.

The whole purpose for spinning a projectile is to allow stabilized flight through air to minimise the negative effects of air. Without air, RPM is a non factor. No bullet spin or over spin, good balance or bad balance, all slugs would fly true in a vacuum. So air REALLY causes all inaccuracy, not RPMs. Assuming a bullet exits at the same point in the harmonic position of a barrel which handguns do not deal with. But handguns do see barrel time and recoil as similar effects to harmonics.

Do anything to increase air resistance by a bullet at launch, whether that be poor balance, increased twist rate angle, or increased velocity and RPM, all increases air resistance.

Easiest accuracy occurs at the point that rotation is sufficient for the length of the slug to stabilize it at the lowest .... velocity .... possible that is required to reach the distance of interest. Anything above and beyond that point magnifies wind resistance and inaccuracy. You can have just as lousy accuracy at low velocity / RPMs as high all because of air. If you can manage to launch a cast bullet true, 200,000 RPMs won't affect it. I need a bigger case to go faster to tell you where the top actually is. Right now I have a 625-2 that is RPMing me to death. But I will beat it. :grin:

Larry Gibson

04-29-2008, 03:20 AM

I think this is the wrong approach and I am going to come at this from a different angle.

Let's reverse the thought process and define slow problems first.

Take a wadcutter out of a handgun. Poor BC. Even though RPM loss is minimal, a perfectly stabilized wadcutter destabilizes and becomes in accurate fairly quickly. Why? Can't be RPMs making it go wild. Must be air resistance. So the answer is to increase RPM with a faster twist rate to compensate for stabilization. Cause if you try to drive the wadcutter faster, it will lose accuracy at the same RPM that a faster twist would stabilize it at a lower velocity.

Take that wadcutter and put a nose on it. Now it's called a semi wadcutter. This improves BC and bullet balance by making it easier to stabilize with weight shifted to the rear of center. But not necessarily making it more accurate at close range distances. Just easier to drive faster. Load that with a low power charge and it too will lose stability at fairly short distance, probably at a longer range than the wadcutter. RPMs remain constant there too, over this short distance but air (wind) really causes the inaccuracy. Shoot 7 grains of Green Dot in a 44 Mag with a 250 Keith in several guns with the same exact twist rate and all will have the load go wild at different distances even though RPMs and velocity are fairly close to the same level.

Same as some 38 twist rifles that can launch 300 grain bullets well and others that can't at the same velocity level, the same (low) RPM level. Can't be too low or no guns would perform well. The typical velocity range for these handgun loads (above) that air affected them, are less than 1000 fps. This equates to 788 MPH. Now when accuracy is lost, these results are fairly understood. Over RPMs are not involved in the inaccuracy. The slugs became destabilized even though RPMs were constant causing air to have more effect. Increasing the velocity of poor BC slugs makes it more difficult to obtain accuracy when it is easier to simply spin it faster with a faster twist if stabilization is necessary.

All basically correct. However what you are discussing is the minimal amount of velocity required to maintain stability. Each design has it's own limitations at the bottom end. Nothing new there. What does this have to do with cast rifle bullets at the velocities we are discussing. Stabilization is not the issue.

But change to rifles .... and we lose our common sense when velocity really increases. Air goes from having a major effect on accuracy on a poor BC at low velocity to having ZERO effect what so ever when we double or tripple veliocity.

I have no idea where you get this idea?

Load and pressure means nothing to launch at these levels when we KNOW it does in really low levels of both RPMS and pressure. The fact that LArry shoots my bullets differently in his guns is the fault of RPMs and not the mechanical difference in the guns that we readily understand at low levels. Our ignorance cause us to look for excuses.

Again i'll refer you to the fact that I am comparing the proportional difference in accuracy with the same rifle. I am not comparing the accuracy of my rifle against yours. I also am looking for consistant results. Not something that can only be done under limited circumstance with one rifle. Also I'll remind you this is test is about regular designs of cast bullets, not custom made ones for a specific cartridge/barrel/throat. You might also remember I have already agreed that acceptable accuracy can be had above the RPM threshold. I've asked you many times to take a 311291 and shoot it in increments from 1700 fps to 2500 fps with a powder of your choosing in your own '06 with 10" twist and to show us the 5 shot groups. You've not done so because you know what the results will be. And those results will substantiate the RPM threshold.

Is there a sweet spot for for RPMS? Same question can be asked is there a sweet spot for velocity? And what happens if we increase wind resistance by increasing bullet diameter? We lower the ideal RPM or velocity level. Which means we lower the accurate velocity level. Even though 22s are the hardest to mold well, (balance) they have the highest velocity potential. An inaccurate 22 caliber (jacketed or cast) is most often more accurate than a 30 caliber at the same RPM level. Why? Has to be less wind resistance, cause it is just as highly a destabilized slug or worse.

The whole purpose for spinning a projectile is to allow stabilized flight through air to minimise the negative effects of air. Without air, RPM is a non factor. No bullet spin or over spin, good balance or bad balance, all slugs would fly true in a vacuum.

Quite untrue. The centrifugal force acts the same; in air or in a vacuum. How is it do you suppose a spinning space station "creates" gravity without air?

So air REALLY causes all inaccuracy, not RPMs. Assuming a bullet exits at the same point in the harmonic position of a barrel which handguns do not deal with. But handguns do see barrel time and recoil as similar effects to harmonics.

Could you run a test to prove this hypothysis or at least provide some scientific proof? I really think you're in left field here Bass.

Do anything to increase air resistance by a bullet at launch, whether that be poor balance, increased twist rate angle, or increased velocity and RPM, all increases air resistance.

Easiest accuracy occurs at the point that rotation is sufficient for the length of the slug to stabilize it at the lowest .... velocity .... possible that is required to reach the distance of interest. Anything above and beyond that point magnifies wind resistance and inaccuracy.

It is quite proven that given equal shapes (BCs) the fastest bullet is less effected by wind.

You can have just as lousy accuracy at low velocity / RPMs as high all because of air. If you can manage to launch a cast bullet true, 200,000 RPMs won't affect it. I need a bigger case to go faster to tell you where the top actually is. Right now I have a 625-2 that is RPMing me to death. But I will beat it. :grin:

First it was pressure, then it was "nodes" then it was rifling pitch and now it is all about air! I really don't think so but perhaps the air is different where you shoot.

Larry Gibson

Tiger

04-29-2008, 11:37 AM

Larry

I think this is what Bass is getting at: If a spinning object is truly free of outside torques--the influences that affect rotation--then it will spin forever. Angular momentum is a conserved quantity in our universe, meaning that it can't be created or destroyed and can only be transferred between objects. Thus if you set an object spinning (by exerting a torque on it) and then leave it entirely alone, it will not be able to change its angular momentum. The earth is a good example of this situation--it's almost free of torques and so it spins steadily about a fixed axis in space. Its angular momentum is essentially unchanging.

Since gravity acts at the center of rotation of a freely falling object (which is that object's center of mass), gravity exerts no torque on freely falling objects. Because of that fact, even objects in orbit around the earth are essentially free of torques and satellites that are set spinning when they're launched continue to spin steadily for centuries. The space shuttle astronauts encounter this result each time they release or catch a satellite. If they set it spinning when they let go of it, it will still be spinning when they retrieve it years later.

Centrifugal force is a ghost force...it does not exist!
Centrifugal force is not a force at all, it's a lack-of-centripetal force.

The gravity on a spinning space station is not a true gravity, it is only stimulated.

The bullets that you are using that lose their accuracy which you blame on their rpm threshold are through imperfections in the casting of the bullets and/or deformation while still in the bore. There can be many things to defore it in the bore and these deformations can be to base, gas cutting, slump, compression, incomplete or uneven obturation. You get the point. Then when the bullet exits the barrel all these items get acted upon by the rpm, air, velocity, and gravity.

Thinking about what I wrote above does it now make more sense why a zinc bullet can out do the cast lead alloy bullet at high velocity and rpm?
One thing that is eliminated is the zinc bullet has less deformation in the bore.

Now Larry you must do the test over again with a different alloy and guess what? After that you still must do it all over again with yet another alloy.

Larry there is no simple way to put except that you are wrong.

Ralf

joeb33050

04-29-2008, 12:49 PM

Larry

Larry there is no simple way to put except that you are wrong.

Ralf

I wish that I as this sure about things. Specially cast bullet things.
joe b.

Tiger

04-29-2008, 01:08 PM

I wish that I as this sure about things. Specially cast bullet things.
joe b.

Joeb

......and this helps us how?

Ralf

Larry Gibson

04-29-2008, 02:02 PM

QUOTE=Tiger;330857]Larry

I think this is what Bass is getting at: If a spinning object is truly free of outside torques--the influences that affect rotation--then it will spin forever. Angular momentum is a conserved quantity in our universe, meaning that it can't be created or destroyed and can only be transferred between objects. Thus if you set an object spinning (by exerting a torque on it) and then leave it entirely alone, it will not be able to change its angular momentum. The earth is a good example of this situation--it's almost free of torques and so it spins steadily about a fixed axis in space. Its angular momentum is essentially unchanging.

Since gravity acts at the center of rotation of a freely falling object (which is that object's center of mass), gravity exerts no torque on freely falling objects. Because of that fact, even objects in orbit around the earth are essentially free of torques and satellites that are set spinning when they're launched continue to spin steadily for centuries. The space shuttle astronauts encounter this result each time they release or catch a satellite. If they set it spinning when they let go of it, it will still be spinning when they retrieve it years later.

It is known that the rotaional spin of a bullet slows down very, very little over the time of it's flight. Satelites orbits also decay because their spinning also slows down over time (among other reasons). I really fail to see what the point of this is in relation to what we are discussing.

Centrifugal force is a ghost force...it does not exist!
Centrifugal force is not a force at all, it's a lack-of-centripetal force.

Wikpedia's discertation is not correct. You feel centrifugal force every time you turn a sharp corner in your car. It does exist.

The gravity on a spinning space station is not a true gravity, it is only stimulated.

That is quite true (simulated not "stimulated" though) but the "simulated" force is actually centrifugal force. Your statement here contradicts your previous statement that centrifugal force does not exist.

The bullets that you are using that lose their accuracy which you blame on their rpm threshold are through imperfections in the casting of the bullets and/or deformation while still in the bore. There can be many things to defore it in the bore and these deformations can be to base, gas cutting, slump, compression, incomplete or uneven obturation. You get the point. Then when the bullet exits the barrel all these items get acted upon by the rpm, air, velocity, and gravity.

The factual evidence of the tests and previous experience of many, many shooters proves your line of thinking to be wrong. Granted that casting imperfections and defects caused by acceleration unbalance the bullet but it is the affect of RPM on those imbalances that causes inaccuracy. If it was just the defects created in the barrel or on exit from the barrel then exhibited inacuracy would occur on a linear scale as velocity and pressure increase. The fact is it does not. Accuracy is very good below and up into or even a little ablove the RPM threshold (depending on alloy and powder used). Accuracy actually can and most often does improve as we approch the RPM threshold. Then at some point accuracy seriously goes south. The decrease in accuracy is not linear but increases dractically as velocity/RPM increase. The tests demonstrate this as does the experience of countless shooters for decades. I believe this inaccuracy is caused by the centrifugal force created by higher RPM which over comes the rotational stability of the bullet. I am conducting tests to prove or to disprove that.

Thinking about what I wrote above does it now make more sense why a zinc bullet can out do the cast lead alloy bullet at high velocity and rpm?
One thing that is eliminated is the zinc bullet has less deformation in the bore.

Have you actually shot any zinc cast bullets? I have and when cast in a regular bullet mould like 311291 they to suffer from RPM though the threshold is higher. Casting bullets of linotype is the same. Jacketed bullets and PP'd hard cast bullets do not seem to suffer from this effect. It appears that only cast bullets do. We are attempting to determine why.

Now Larry you must do the test over again with a different alloy and guess what? After that you still must do it all over again with yet another alloy.

Larry there is no simple way to put except that you are wrong.

Wheter I am right or wrong will be determined by the facts of actual testing, not by your predisposed thoughts.

Larry Gibson

Tiger

04-29-2008, 02:23 PM

Hallo again Larry,

I meant simulated instead of stimulated thanks for catching that.

Larry you really need to go into the internet and study centrifugal force and all if it's associated parameters. Try to find one written by a physicist. You really don't know what you are talking about. Centrifugal force is what a person feels or better yet how a person describes what he feels when being spun in some type of machinery. The amusement park ride where you stand strapped against a wall the ride spins you then the floor drops from under you.

Yes I have shot zinc bullets and they are hard to cast as far as cutting the sprues and they are hard on the molds. Why you suppose their rpm threshold is higher Larry? Do you think perhaps some of the detrimental influences done to them in the bore are gone? In other word that the bullet is not damaged as much in the bore as a lead alloy. So think Larry what happens to the lead alloy bullet that is not happening to zinc bullet or the jacketed bullet. Let me throw this thought at you. Cut copper rings that fit inside lube grooves on a mold. These bullets if they are done correctly will shoot higher velocity thus your rpm and more accurately. Why Larry?

My ideas are not supposed. My ideas are reality in my cast shooting as are for a few here on this forum.

Ralf

Larry I edited this in. Here are three places to give you more idea on centrifugal force.
http://regentsprep.org/Regents/physics/phys06/bcentrif/centrif.htm

http://phun.physics.virginia.edu/topics/centrifugal.html

http://www.britannica.com/eb/article-9022100/centrifugal-force

I think Wekipedia is one of the worse places to get factual information from.

Larry Gibson

04-29-2008, 02:54 PM

Ralf

Here's the problem with everyone who says centrifugal force does not exist. The following is a quote from one of your sources It best typifies the usual explanation.

"It is important to note that the centrifugal force does not actually exist. We feel it, because we are in a non-inertial coordinate system. Nevertheless, it appears quite real to the object being rotated. This is because the object believes that it is in a non-accelerating situation, when in fact it is not. For instance, a child on a merry-go-round is not experiencing any real force outward, but he/she must exert a force to keep from flying off the merry-go-round. Because the centrifugal force appears so real, it is often very useful to use as if it were real"

If centrifugal force does not exist then just exactly what is it that causes the child to fly off the merry-go-round? Note that the child must exert a counter force to this "non-existant force" to keep from flying off in the very description of something that doesn't exist. How is that? Then the last sentence is the catch all caveat; .it is often very useful to use as if it were real".

Reminds me of the witch doctor who tells his warriors his potion makes them bullet proof unless, of course they drink beer, jack off or otherwise have bad thoughts. Then after they all get shot. the witch doctor can say; hey they must have drank beer, jacked off or otherwise had bad thoughts. So ok if centrifugal force does not exist then it is the effects of that non-existant force caused by RPM that we can assume "is often very useful to use as if it were real".

The effect is real.

The threshold is higher with zinc bullets because there are less defects for the non'existant centrifugal force to act upon as if it were real. I see by your question; "Why you suppose their rpm threshold is higher Larry?" that you do understand there is an RPM threshold.

Larry Gibson

Tiger

04-29-2008, 03:02 PM

Larry,

Yes I do have a rpm threshold. It is called unlimited. Lead alloy can reach this same zinc area with paying attention to every detail.

You just do not get the forces of nature. You only pick from them what you want to believe not the entire picture. Same with your rpm threshold.
You pick the rpm as the great accuracy destroyer but yet you admit to bullet defects being the cause too. Everything is connected Larry. I could start a thread about the bullet defect threshold. What would be the difference? Or the BC threshold. See what I mean Larry?

Ralf

Larry Gibson

04-29-2008, 04:23 PM

No Ralf, I don't see what you mean.

Why don't you convince me. How about you cast up some 311291, 311041, 30-180s or what ever like mould you have....or better yet, how about in any caliber. You cast up some bullets and shoot them from 1600 to 2500 fps (you say "unlimited" but I'll give you a sporting chance) in a 10" twist rifle in increments of 100 fps or so and shoot 5 shot groups at 100 yards. Load them with whatever powder you choose, using what ever alloy you choose, whatever lube you choose and whatever GC you choose. Use any loading technique you want. Then show us the load data, the velocity and the corresponding groups.

Continuously you tell me I'm wrong even though my test data is showing I'm right. You continuously tell us how you can do it but do not present any data or actual facts. So far I've mostly seen just obnoxious replies from you. So how about it, put up or shut up.

Larry Gibson

Tiger

04-29-2008, 04:51 PM

Larry

I thought I spin in one more time before bed. How you like that on topic beginning?

I don't have to prove anything to anyone. That's how it alway is here on cast boolits. I think Albert Einstein have to prove E equals MC squared to hey?

This is your thread and so far you have proved nothing. You have not nailed anything on the head yet. You think you have but you have not.

I am here because I hope that myself and others can prevent you from polluting the minds of the novice cast shooter which your unprovable threshold theory. Your fancy tests so far have not shown rpm is the amazing great destroyer of accuracy.

Ralf

Larry Gibson

04-29-2008, 05:10 PM

Bass Ackward

04-30-2008, 09:10 AM

Well there is a sure fire test to see if accuracy loss occurs at the muzzle or if RPMS are the issue. Cause RPMs do not slow down. So if they negatively impact the unbalanced bullet, then they will continue to impact the slug through out flight. Cause over RPMS is over RPMS the whole distance of flight?

Shoot the same loads that failed at 50, 100, and 200 yards. If accuracy is linear, and to define that I mean 50 yards is 1/2 of 100 yards and 200 yards is twice as much, then ALL accuracy loss is occurring at the muzzle for other reasons before RPMS takes hold of the slug.

IF RPMs is the issue, then groups should get DRAMATICALLY worse as the distance is increased because bullet balance remains what it is all the way to the target. Now I never see this unless a slug is under stabilized, NEVER over because my accuracy remains linear until velocity slows enough the UNDER stabilization cause wacky issues.

This test is a down and dirty test to eliminate RPMS from the inaccuracy discussion.

If the groups turn out to be linear, then accuracy loss is occurring only at the muzzle release and this CAN"T be RPMs. Simple as that.

Bass Ackward

04-30-2008, 09:14 AM

First it was pressure, then it was "nodes" then it was rifling pitch and now it is all about air! I really don't think so but perhaps the air is different where you shoot.

Larry Gibson

Larry,

I am trying to get you to understand that this is a complicated issue that there are more factors than RPMS. IF you run the test I gave you above, you can throw out RPMS as an Enemy because it will be RPMS that CORRECT the bullets flight to a linear trajectory.

RPMs are your friend, not the enemy.

Tiger

04-30-2008, 10:58 AM

Ralf

That's just about the answer I thought you'd give. You won't put up because you're afraid of what the results will be. Since you have stated your objective I see no further use in wasting time on you. Those who read this thread and subsequent threads regarding the RPM and its effects on cast bullets will no doubt make up their own minds as to whose mind is polluted.

BTW; the Japenese discovered the proof of E= MC squared in late 1945, twice to be exact.

Larry Gibson

Larry

I say too that is the answer I thought you would say. So you want me to take a rifle with a fast twist and go out and consistently shoot small accurate groups at very high velocity and rpm hey? I have done that. I believe so have 45 2.1, Bass, and others.

Yes the two atomic bombs were prove of Einsteins theory, but was proved much early before that like in 1930 with first nuclear fission. I just mentioned him because when someone does they don't doubt him.

Bass has just stated something is very interesting. If the rpm alone is the bigger of the accuracy destroyers, he is right in saying why would it only destroy accuracy a little bit. Why not destroy it bigger. Destroy it altogether. Probably because like Bass say rpm is your friend. It is why you get accuracy to start with. Maybe way back in black powder day someone thing to put grooves in barrel. Yes Larry I know that it was for the intentions to collect and prevent so much fouling. But back to this man. He shoots and looks at his target. He is amazed. He go back home and gather all the male members of the village for ancient type forum talk. He tell them he think he just found a rpm threshold. Much like you Larry.

Larry I am new here. But I get pm's about how wrong you are from some of the very respected members of castboolits. They do not want to get involved in the silly mess.

Ralf

Larry Gibson

04-30-2008, 02:39 PM

Bass

First let us remember that accuracy with any bullet is not strictly linear, groups do get larger as range increases. In other words a load with a good bullet that shoots 1/2" at 50 yards will not necessarily shoot 1" at 100 yards and 2" at 200 yards. The better the quality of bullet the closer it will be given proper stabilization. It may shoot ½” at 50 yards 1.1” at 100 yards and 2.4” at 200 yards. Remember how many times I've said; "all bullets when fired are unbalanced and are affected by RPM. That's why we shoot groups instead of all shots going into one hole." That is because RPM adversely affects the flight of all bullets. BTW; I didn’t dream that up, it has been known for a long time. With the exception of regular cast bullets all the other bullets do seem to follow a close to linear expansion (or at least a slight parabolic curve) of groups as range increases. Regular cast bullets on the other hand when pushed to a certain point (somewhere in the RPM threshold) do not. What I am trying to find out with my tests is why regular cast bullets inaccuracy is not linear as velocity is increased through and above the RPM threshold.

Thus I think your test would be valid. But the test load would have to be one that was above that point in the RPM threshold where accuracy was really adversely affected. One of the loads where the accuracy loss was non-linear on the graphs should be used along side an accurate load that is in or below the RPM threshold. I would expect the accuracy loads groups to be relatively linear and the high RPM groups to get substantially larger as the range increases.

Now you say you "never" see this. Well I have. I've seen it numerous times where accuracy was good at 50 yards but horrible at 100 yards. I'm sure many others have too. This is why I always recommend testing at a minimum of 100 yards and preferably then confirmed at the longest range you are really going to shoot at.

So are you going to run the test? You might want to so.

If not then it will be a couple weeks before I can get to it. I have to replace the water heater which is in the garage so my reloading area has been moved for that. I also will be gone back to Camp Lejeune for a couple weeks. I probably will be back on the 11th or 12th. If I do the test I will conduct a side by side test with two loads out of the 10" twist rifle. One load will be the accuracy load of 28 gr H4895 which is down in the RPM threshold at 1894 fps. The second load will be with the 38 gr H4895 load which is above the RPM threshold at 2491 fps. Would that meet the criteria for your test?

Larry Gibson

Tiger

04-30-2008, 02:46 PM

Larry

Much to think. I like what you say to Bass. I think reverse of what you say and look at what they call bullet goes to sleep? I would like hear your explanation of how bullet shoots terrible groups at close distances and then much further out it get better lots better.

I think too that no matter how well we put together cartridge that no two cartridge are exactly the same in performance. Even when fired from a solid machine rest they can not achieve that one bullet diameter hole you wrote of. There too many variables like neck tension, perfection of the bullet, does each kernel of the powder burn exact same. You know what I mean Larry.I think that if ever benchrest shoot one bullet diameter hole I would not believe it. I think it a fluke. Unless it can be repeated reliably. What think you Larry?

Ralf

Larry Gibson

04-30-2008, 02:46 PM

Ralf

You say you have "done it". I have posted my test results. Once again I'll ask you to post your test results, if you have really "done it". If not then as they say; money talks, b*llsh*t walks.

As to private PMs; I've got numerous of them too. So what? PMs do not change the facts of the tests I have run. Opinions are like (you know what), everyone has one.

Can anyone tell me why I continue to waste my time on Ralf?

Larry Gibson

Larry Gibson

04-30-2008, 02:49 PM

Maybe because I like him as he keeps coming back for more?

Larry Gibson

Scrounger

04-30-2008, 02:55 PM

Larry, I can only tell you it takes two to have an argument. (Or discussion if you prefer) If you wish to end it, all you have to do is quit responding on that thread. I think most of us lost interest in it several weeks ago. I agree with your theory, by the way, but he is probably correct that some other factors may sometimes alter the outcome. As Forrest Gump says,"____ happens."

onceabull

04-30-2008, 03:09 PM

"Tiger" -"Ralf" sez: "I am here because I hope that myself and others can prevent you from polluting the minds of---------------". That helps, he is here to save us from OURSELVES !! And this from a guy that cited "starmetal's"(aka "joe", MaxPayne, et al) work as though it was a credible source..:twisted: Onceabull

Larry Gibson

04-30-2008, 03:25 PM

OK guys, I guess that's it for this thread. I will post Chapter 3 when the tests are done.

In defense of Ralf, Leftiye and others; this is a forum and as such it is always open for argument or discussion. I presented an idea and have backed it up with actual tests. Others disagree with that idea and I must be able to defend that idea. That's how some advances in what we really know are made. I may be right and I may end up proving my idea about a RPM threshold wrong. Either way we gain some knowledge along the way. We can sit around and hypothesize all day long but that does not mean what we think is right. If we are to learn we must be able to substantiate those hypothesis. So far I am substantiating mine.

Larry Gibson

Larry Gibson

04-30-2008, 03:27 PM

Last post on this thread;

Bass

As I am through on this thread shall we take the test you suggested to a new thread or convey via PM?

Larry Gibson

leftiye

04-30-2008, 03:57 PM

I notice you didn't answer B.A. !?!?!? - either! Want to take it to PMs. (you did just mention me didn't you? So I get to post?) Concepts Larry, "deal with them or die" (- Or was that "Publish or die?") Test Results are fine, but they aren't discussion, nor are they argumentation.

Larry Gibson

04-30-2008, 04:06 PM

Leftiye

What part of my posts to Bass do you not understand? He asked to run a test. I said you or me Bass and proposed how we do it. So what part of that is not an answer. What's with this stupid remark of yours? How about you run the test too?

Larry Gibson

Tiger

04-30-2008, 04:17 PM

Larry

Sorry see you don't wish to continue. No one can take your place here who I argue with then? :roll:

onceabull

You have problem with me? From search I find Starmetal stuff but who Maxpayne? I find no post in search with that name. I question why you post nothing that has do with rpm but only negative things?

Hey maybe we quit then hey. Maybe some get hot under collar and time for period of cooling.

Ralf

leftiye

04-30-2008, 05:37 PM

leftiye

04-30-2008, 11:17 PM

carpetman

04-30-2008, 11:56 PM

leftyie---I hook up a bullet alarm clock to my bullets so they dont yawn and go to sleep.

Bass Ackward

05-01-2008, 07:24 AM

Last post on this thread;

Bass

As I am through on this thread shall we take the test you suggested to a new thread or convey via PM?

Larry Gibson

Larry,

The short answer is no. Since you have the three rifles with three different twists, and are continuing the tests, you are the one with credibility here, and if the inaccuracy you are seeing or reporting on needs to come from you.

Larry Gibson

05-01-2008, 10:27 AM

Larry,

The short answer is no. Since you have the three rifles with three different twists, and are continuing the tests, you are the one with credibility here, and if the inaccuracy you are seeing or reporting on needs to come from you.

Very well Bass, I shall include that test in with the others. This is getting to be a long series of tests.

Larry Gibson

Larry Gibson

05-01-2008, 10:38 AM

Larry,
The concept that groups do (almost always) open up LINEARLY flat blows you out of the water. As Bass says, If rpms were doing the causing of the inaccuracy, groups would open up exponentially, because the RPMS would CONTINUE to cause more inaccuracy to be added to the already existing deflection (because RPMS don't slow down much with distance they would continue to deflect more and more over distance.) and group size at doubled distances would not be only double in size but probly be in the range of four times the size of the previous group. Even those loads that are poor in accuracy open up LINEARLY. Even if they have lost accuracy due to increased velocity. Curious that you wouldn't answer that, I"d say. (stupid statement over)

Leftiye

Once again you fail to understand what was said and you have once again ignored the results of the test. The groups of the test do not open up in a linear fashion when velocity is increased and they are targeted at 100 yards. The test that Bass suggests is to test the groups of one load (one velocity/one RPM) that is above the RPM threshold at 3 different ranges. If the groups size increase in a linear fashion then Bass could be correct. If the groups increase larger than linear would suggest then RPM is adversely effecting the. We still haven't answered the question as to RPM above the threshold causing the bullets to "cork screw" (opposite of "going to sleep") in flight.

As to "stupid statement" if you are referring to your own statement you are correct.

Larry Gibson

Larry Gibson

05-01-2008, 10:41 AM

What does the fact that boolits "go to sleep" (just as tops do) over distance say in this context? They start out yawing, and then settle down. Wouldn't Rpms aggravating out of balance get worse and eventually tumble? In this scenario, the reality is that 200 yard groups are often SMALLER than 100 yard groups.

Due to the exhibited consistancy of the BCs it appears the RPMs are not causing additional yawing, pitching of woblle but are causing the bullets to cork screw as previously mentioned. This has yet to be proven but further testing will do that.

Larry Gibson

Tiger

05-01-2008, 11:44 AM

Larry,

I am glad you are back. Remember I tell you that you test require much shooting? You just say that.

Larry tell me your idea on the sleeping bullet. I explain first. A shooter find his group is much better at a farther distance like 200 or 300 yards then it is at the 100 yard mark. Some claim the bullet has not yet stabilized it self at that close distance and when much farther away it go sleep as they say. My question is if it so unstabilized why do not the rpm just make it much worse? I think to the gyroscope. If you disturb it becomes unstable. If you disturb it enough it go crazy and fly off. But if you disturb it just a little it wobble some then regain it steady spin again. You think maybe this what happens to so called go to sleep bullet?

Ralf

leftiye

05-01-2008, 12:29 PM

Larry Gibson

05-01-2008, 12:45 PM

Ralf

I am plumb amazed, an intelligent question/explanation in the second paragraph instead of the obnoxiousness as in the first. That is refreshing to say the least!

First if you will read Chapter 1 you will see my inference that the test will take a lot of shooting. I believe I also mentioned the number of rounds fired in the first test. Like I need you to tell me what I already know?

Bullets that "go to sleep" is an interesting subject. I believe it was Elmer Keith reporting on the .333 OKH that first brought this up. I've had several shooters report this to me and attempt to prove it. Seems all had scopes with parallax adjusted farther than 100 yards. When the scopes were parallax adjusted to the proper range the groups were linear as range increased. I though the concept a myth until I first worked with slow twist Palma barrels some years back and using M80 ball ammo (that was required for Palma matches back then).

When using iron sights (no parallax involved) 10 shot groups at 100 yards were very often the same as 10 shot groups at 200 yards. Score books were kept recording each shot. At 600 yards, 800, 900 and 1000 yards the groups increased in a linear fashion (again not exactly linear but with the expected results). The range we were using had target holders at 100 yards and 100 meters or roughly 10 yards between them. One target was placed behind the other at these two ranges. The 100 yard target was just the paper target with no backing to avoid deflecting the bullets as much as possible. The bullet hits in the groups was the same in the two targets. It was observed (confirmed with a retest) that the group of the second target was rotated about 30 degrees clockwise. This gave a real indication that all the bullets were cork screwing in flight. It did not appear that the bullets themselves were unstable and were flying point on. Instead it appears the path of the bullet was one of a cork screw flight instead of a straight line.

Whether the flight of the bullet straightened out (went to sleep) at some range or the cork screw flight simply became smaller than the linear dispersion of the group was not determined in our limited test. It was the consensus of opinion at the time that the bullets still corkscrewed in flight. I tend to agree but am waiting for some definitive testing to prove it one way or the other. I’m not sure the concept is a myth, is real or just a misconception of what is really happening.

Thus it may be the same with cast bullets when they go above their own RPM threshold. They simply fly point on but their flight path begins to cork screw. The higher the RPM above the threshold the larger the corkscrew and the larger group dispersion becomes. I’m not even sure if cast bullets at very high velocity/RPM actually go unstable. I’ve shot some cast bullets of 150-180 gr out of a 10” twist ’06 at 2700-2800 fps that gave 16-30” groups at 100 yards yet the bullet holes were very round giving no indication of tumbling. Granted they pass through the target very quickly but still there was no sign of tumbling.

Those are my ideas or thoughts regarding bullets “going to sleep”.

Larry Gibson

leftiye

05-01-2008, 01:13 PM

My understanding of corkscrewing is that it is the manifestation of the bullet yawing, and that as the boolit rotates while yawing air pressure deflects the bullet into a spiral path. Not to be argumentative, just that the bullet isn't flying point on when it yaws.

Corkscrewing is also what often happens when a bullet hits an obstruction and is not completely knocked @$$ over teakettle, and the bullets flight then in many cases is an expanding spiral.

Tiger

05-01-2008, 01:16 PM

Larry,

I have seen this happen. One time reading magazine an article on a new tactical type Weatherby rifle. Very expensive. I surprised the author criticize the rifle. At 100 yards the groups were very bad. He think for that much money this should shoot better. Fortunately he shoot as 300 yards. Then the groups look like good groups for 100 yards. He concludes the bullets going to sleep.

Your paper targets with no backs make me think of story a military veteran tell me. He say if you hang pure silk scarf on clothes line let hang free an shoot at it with any high power rifle that the bullet not put a hole through it because air wave in front of bullet push scarf away. I never try this as I don't believe it. You ever hear such thing?

Ralf

Larry Gibson

05-01-2008, 01:22 PM

Ralf

Many think of the bullet going to sleep under such circumstances without realising the scope has parallax at shorter ranges. Never heard of the silk scarf trick. Not going to try it either. If it isn't right and I put a hole in a silk scarf the wife would shoot me!

Larry Gibson

Pat I.

05-01-2008, 03:58 PM

Larry,

I have seen this happen. One time reading magazine an article on a new tactical type Weatherby rifle. Very expensive. I surprised the author criticize the rifle. At 100 yards the groups were very bad. He think for that much money this should shoot better. Fortunately he shoot as 300 yards. Then the groups look like good groups for 100 yards. He concludes the bullets going to sleep.

I don't believe that for a second unless the wind pushed the bullets back together. Even if the bullets did go to sleep they're still going to follow their 100 yd flight plan and be much worse at 300, that is unless someone's behind a little steering wheel steering them back in.

leftiye

05-01-2008, 04:00 PM

Maybe not on subject, BUT- - (eh?) I guess it's not such a rare or unusual thing, but I once tried to shoot a group in a plastic bucket with one of my 22-250s. Couldn't make a hole in the plastic. You'd hear the bullet hit, but no hole. I don't think it was just bullet frangibility, but probly also the plastic giving way just a bit at the critical moment. Just FWIW.

Tiger

05-01-2008, 04:37 PM

Tiger

05-01-2008, 04:41 PM

Larry

Larry I find good site for you to look at. Please do not tell me you have seen already. Especially read subjects in Contents.

http://www.nennstiel-ruprecht.de/bullfly/index.htm

Ralf

runfiverun

05-01-2008, 06:30 PM

Larry Gibson

05-01-2008, 06:51 PM

Larry,

"The concept that groups open up linearly" and etc.. Sorry, should have said fact.

Please stop doing that! My comment didn't have anything to do with your test results, it was about what we ALL know happens - not the armchair wisdom, but the observed facts seen by every shooter who has ever shot groups. They DO open up linearly, always have (and hopefully they always will!). I didn't fail to understand anything, neither did you. But you chose to stray from what was said, not me. Excuse me, but as usual. Excuse me again, but "Stupid" is a quote from yourself (don't forget). Not obnoxious, just irritated by your distortions.

How could I fail to understand what was said when I wasn't referring to anything you (or anybody else) said?! Deal with the concepts Larry. Don't quote the liturgy.

So, corkscrewing wouldn't show up as a reduced B.C. number? The boolit IS travleing further isn't it?

Ok, so what did you mean? If you are saying that the groups from normally accurate loads open linearly then we agree. If you are saying that groups from those inaccurate cast bullet loads exceeding the RPM threshold will also open linearly then that assumption is what the test Bass and I are talking about will determine. My experience over shooting such loads at longer range to see if they would "go to sleep" is that groups will increase in size in a very much non-linear fashion as the range is increased. If all that is not what you’re talking about then you've lost me as I then fail to understand your "concept".

Yes, if the bullet is cork screwing the bullet is traveling farther. The measured BCs in fact begin to show smaller BCs as the groups get larger. The BCs are expected to get smaller as velocity is increased but there appears to be a higher rate with the faster twists. If we stretch the cork screw out how much farther the bullet actually travels I do not know. I’m sure there is a math wizard here that could tell us.

Larry Gibson

Larry Gibson

05-01-2008, 06:52 PM

Larry Gibson

05-01-2008, 07:05 PM

Larry

Larry I find good site for you to look at. Please do not tell me you have seen already. Especially read subjects in Contents.

http://www.nennstiel-ruprecht.de/bullfly/index.htm

Ralf

Sorry to tell you this Ralf, that has been one of my "favorites" for some time. If you "Especially read subjects in Contents" you may notice a great similarity between what you read there and what I've posted here.

Larry Gibson

Larry Gibson

05-01-2008, 07:11 PM

larry that 38gr load is a good choice!!!!
might be a reason on why i shoot 37gr in my 308 after going up to 39gr
it was noticeable at even 50 yds.
i appreciate all the work you are doing, and especially the extra effort with yet another
"test"
hope my 4 yr prediction is false,,,,,,,lol,,,,

Thanks. I'm not sure of the necessity to run the test in all 3 twist barrels. I would think that the 28 & 38 gr loads shot in the 10" twist at 50, 100 and 200 yards would be definative enough.

Bass, if your'e reading this why the mention of all 3 barrels for this test?

Larry Gibson

405

05-01-2008, 07:19 PM

leftiye

05-01-2008, 08:07 PM

"Perhaps your "understanding" is not all inclusive." - Larry Gibson.

Well that answered the issue perfectly, didn't it?

Haysoos, Larry, give it a rest! Do you know anybody whose understanding is "all inclusive"? Even thine, as exalted as thou art?

I was only stating my understanding. I think it is correct. Don't denigrate me, PROVE ME WRONG (if you can)!

See what I mean? Issues and concepts Larry, Issues and concepts! Not ad hominem arguments.

Larry Gibson

05-01-2008, 08:14 PM

Or so the saying goes reference accurate cast bullet shooting.

Couple of interesting things being batted around. Yawing instability increases should show in increasing BCs. Could be that the test design sensitivity or equipment is adequate to show increased group size but inadequate to show changes in BC correlating to yawing or other bullet instability. Very interesing stuff!

If on the other hand RPM increases are inducing larger spiral bullet paths to target while the bullet is still aerodynamically efficient and pointed in the right direction... then BC changes probably wouldn't show up and would be very, very small. If that is the theory behind the RPM threshold then it seems something like a "Rotationally Induced Precessional or Perturbational, Escalating, Harmonic Magnus Effect" is in play. Sorry, best terminology I could come up with to explain the theory. Whew! that is getting into some serious and complex physics. Without equally serious test equipment and expert help I wouldn't have a clue as to how to tackle explaining it or testing the theory.

BTW agree with PatI.... even if bullet gyroscopic precessional reduction or "settling down" or "going to sleep" or whatever it's called happens between muzzle and target--> there is no way relative group sizes will get better with increasing distance. The best one could hope for is a trajectory dispersion curve changing from curvilinear to more nearly linear.

NO expert here just shooting out some more ideas :mrgreen:

405

Outstanding explanation!

I believe the M43 is showing sufficient change in the BCs to demonstrate bullet instability. The BC measurement goes to the third decimal and changes have been consistent between different velocities of the same string. The M43 also gives TOF to the sixth place so if one were mathematically capable one could compute the proportional time of flight differences. For our purposes I think the average BC per string is sufficient.

I think this is exactly what I’ve been trying to say; “RPM increases are inducing larger spiral bullet paths to target while the bullet is still aerodynamically efficient and pointed in the right direction”. I'm not stating for certain that is, in fact, what is happening but there is some evidence pointing that direction.

I also concur on groups getting smaller as the range increases. As I’ve previously stated I’ve seen one instance where groups were pretty much the same at 100 and 200 yards but got larger as the range increased after that. Every other instance where someone demonstrated to me the effect of bullets “going to sleep” either it was not reproducible or the scopes induced the larger groups through parallax. I have seen shadow graphs where bullets exhibited yaw on exit from the barrel but then settled into gyroscopic stability. There was no illusion that they produced smaller groups at longer ranges in the test conclusions however.

Larry Gibson

chaos

05-01-2008, 09:08 PM

Can someone summarize this for me? I tried to read through the thread, but it's giving me a headache.

What's the big deal?

Some bullets work better with different rates of twist.

Maybe I'm just a simpleton..............

Chaos

Larry Gibson

05-01-2008, 09:34 PM

Perhaps your "understanding" is not all inclusive.

Larry Gibson.

Haysoos, Larry, give it a rest! Do you know anybody whose understanding is "all inclusive"? Even thine, as exalted as thou art?

I was only stating my understanding. I think it is correct. Don't denigrate me, PROVE ME WRONG (if you can)!

See what I mean? Issues and concepts Larry, Issues and concepts!

The following is ample demonstration (or "proof" if you will) that there are other "inclusions" in the concept. I percieve that is not all inclusive either.

“RPM increases are inducing larger spiral bullet paths to target while the bullet is still aerodynamically efficient and pointed in the right direction”.

You really need to quit taking things so personal. I was not singling you out in the "pot and kettle" issue nor am I denigrating you now. Merely pointing out that there is more to it than your "understanding". 405 gives a pretty clear idea of what we're talking about.

Let's quit bickering so we can learn here, ok?

Larry Gibson

Larry Gibson

05-01-2008, 11:26 PM

Chaos

That's an honest question. The big deal is this; have you ever loaded bullets for any rifle of say 7x57, 280, 300 Savage, 308, 30-06 or any similar rifle with a 9-12" twist? If so have you loaded them up with "standard" loads in the 1500-1600 fps with, for instance, "the load"? Then have you thought; Gee this is a medium weight bullet for this caliber so I'll just load them up to factory velocity. Boy won't that just be the cat's meow....cast bullets I make myself at factory velocity! The 308 is a good example; with a 175 gr 311291 why shouldn't you get 2550 fps, the same as match ammo with 168-175 gr bullets? Then you start working up loads and you find accuracy is pretty darn good up to 1900-2000 fps. But when you push velocity higher the accuracy gets really bad.......so what the heck you say. This just doesn't make sense. I should be able to shoot the same weight of cast bullet as fast as a jacketed bullet if I don't exceed factory pressure, right?

Well it just doesn't work out that way. Pretty much regardless of the cartridge or caliber accuracy with regular cast bullets out of rifles with faster than 14" twist (9-10" twists in particular) is only good to a certain velocity level and then accuracy goes south. That velocity level is always a considerable amount less than what the cartridge can do with an equal weight jacketed bullet. With 9-10” twist rifles best accuracy is usually found in the 1800-1900 fps range.

So the question is why? For many years the most often reason given has been pressure. However that dog doesn’t’ always hunt. Many times someone asks; I can load my 311359s to 40,000 psi in my M1 Carbine and have excellent accuracy. However when I load them to 40,000 psi in my ’06 accuracy is terrible. The difference is in the M1 Carbine the velocity is 1900 fps and in the ’06 the velocity is 2500+ fps. They are the same pressure right? Yet accuracy is good with one and not with the other. So if it is pressure how can that be? Well if we look at it the M1 carbine has a 16 or 20” twist and the ‘06 has a 10” twist. At the same pressure the bullet is spinning 80,000 RPM and accuracy is good. The same bullet at the same pressure is spinning at 173,000 RPM out of the ’06 and accuracy is bad. There are many such examples if we only look at them.

Thus it appears there is a threshold of RPM where in a regular cast bullet begins to lose accuracy. The questions we seek answer to are; does the RPM threshold exist? What is the inaccuracy actually from? Can we do anything to enable a regular cast bullet to push through the RPM threshold to a higher velocity with accuracy? Those are the questions I seek to answer by conducting actual tests and measuring the variety of specific things mentioned in Chapter 2.

Larry Gibson

D R Greysun

05-01-2008, 11:33 PM

runfiverun

05-01-2008, 11:50 PM

chaos remember this is with plain old cast boolits, with g/c that the guys here can cast
ay home, with lead that can be found made or bought,
no super titanium cores or depleted uranium or paper patching.

just GOOD boolits made as good as possible, with some culling and care in loading.

Larry Gibson

05-02-2008, 12:02 AM

Suggest some head ache inducing reading? :) I think if you can't find an answer to your questions here, you may be asking the wrong questions. :roll:

http://www.nennstiel-ruprecht.de/bullfly/index.htm

D R

That is a very good site and one can learn a lot there. However, as you mention, some headaches may evolve from too much reading at a time. The problem with that site and most all others concerning ballistics is they do not address the questions we seek answers to. Most often if cast bullets are addressed only "pressure" is addressed as the limitation. As mentioned by myself and others, that dog doesn't always hunt.

Still that is a very good site and I have just referred to it. Thanks for the input.

Larry Gibson

Tiger

05-02-2008, 12:15 AM

I don't believe that for a second unless the wind pushed the bullets back together. Even if the bullets did go to sleep they're still going to follow their 100 yd flight plan and be much worse at 300, that is unless someone's behind a little steering wheel steering them back in.

Good morning everyone I write before I go to work.

Pat i

This last paragraph of site I will give you: The difference in muzzle velocity between rounds causes the bullets to
go through the paper at close range at different points of the
spiril. You will see this more frequently as time goes by due to the
numbers of tight twist barrels being used in this fad of shooting overly
heavy, long bullets. Shoot a 55 grain bullet out of a 9 twist barrel
etc. There has been posts in this thread indicating that the dispersion
of shots would be in seconds and minutes of angle proportionate to the
distance checked. Then I ask why not check every thing at short range
and eliminate shooter error. We shot 18000 rounds of 50 cal ammo during
a contract. The guns were sighted in and function tested at 100 yards
and averaged 1.5 moa groups. When these same guns were tested at 600
yards you would expect the groups to run 1.5 moa or 9 inches. The 600
yard targets ran as small as 3 inches and never any larger than 6 inches
as an average. Any that shot larger than 9 inches were inspected and re
tested.

Gale McMillan

Okay now the site: http://yarchive.net/gun/ammo/bullet_helical_path.html

I think McMillan 18000 rounds should be proof enough hey?

Ralf

leftiye

05-02-2008, 02:26 AM

Ralf - Applause!

Same statements made on Joe Brennan's thread - "Do cast boolits blow up". More posts there on this subject. Much disbelief both of phenomenon, and the explanation. FWIW, boolits spiral because of AIR DEFLECTION while yawing (proir to settling down). Yawing boolits DO NOT fly point on - by definition (will leave out the duh).

chaos

05-02-2008, 08:42 AM

Well Larry,
I do understand what you are saying, but I'd never gave it much thought. I've never used cast bullets in Rifle rounds so I never had such terrible problems. When I find a bullet/ powder charge combination that doesnt work for a particular firearm (because of RPMs, twist rate, or the stars not aligning properly), I generally just work up another load for the thing and not waste my time thinking of it anymore.
Quite interesting stuff that you have shown though.

I stole the Baby Jesus in the little manger from my wife's nativity scene. I keep it on my reloading bench. I pray to it each and every time that start a reloading session. So far so good....

Chaos

leftiye

05-02-2008, 12:53 PM

Chaos, - I've gotta say it - your pen name coupled with that avatar really are kinda unsettling - But it's cool.

Larry Gibson

05-02-2008, 01:33 PM

Perhaps groups from bullets that have "spiral bullet paths to target while the bullet is still aerodynamically efficient and pointed in the right direction” do not open up in a linear fashion because they are departing the muzzle on a tangent to what would be a straight trajectory?

Groups were still larger at 600 yards than at 100 yards with McMillan's test.

BTW; the test did not consist of 18,000 rounds fired. The guns were; "The guns were sighted in and function tested at 100 yards and averaged 1.5 moa groups. When these same guns were tested at 600 yards". No doubt a considerable lesser amount of ammunition than 18,000 rounds was used. Depending on the number of guns for the "contract" probably less than 20 shots were used during this test per gun. I've shot numerous of McMillan's "guns" and you just don't sit there and shoot accurately for much more than that. However even if the testing consisted of only 100-200 rounds that is still a fairly good indicator.

Also note that McMillan says the expected norm was a linear sized group from the 100 yards sized group. Any guns not shooting that minimum 9" were re-inspected and retested. He doesn't say how many were rejected or how many actually shot linear sized groups at 600 yards only that 6" was the average. An average of 6” at 600 is still a larger size that 1.5” and is still a linear increase. It’s just not a linear increase based on range increase.

Another thing to consider is the number of shots fired. I have many times seen shooters with target rifles and sniper rifles shoot five shots into 1" at 100 yards and then put 3 shots into 1" at 300 yards. The all want to quit right there and say how good they are and how accurate their rifle is. However when they shoot 5 shot groups at 300 yards the group size expands to 3". My point here is we have to remember we shoot into a cone of fire. Any bullet may hit anywhere within that cone. Just because we can shoot 1" at 100 yards does not mean a bullet fired at 300 yards will hit farther away from the center of the group. Many of them will still hit in the middle of the group and be quite close together.

Still, McMillans comments are interesting.

Larry Gibson

Tiger

05-02-2008, 02:07 PM

Larry you funny. You have answer for everything. I often wonder why you don't have book or some big business in this area. Do work for the military, ammunition manufacture, and big firearm companies.

So then I ask you Larry are there really Aliens on earth? Also I like to know who really assassinated John Kennedy.

I don't wish to disagree with you but like I say you have answer for everything and always answer to the negative of the question or statement.

Ralf

leftiye

05-02-2008, 03:29 PM

Larry, Ye're grasping at straws. Groups for the 6" @ 600Yds if interpolated down to 200 yds. (assuming the NORMAL linear divergence - 6 at 600 would be 5 at 500, and 4 at 400, and so on))would be about 2". Guess what they'd be for 3" groups interpolated back to 200 yds (half of 2" - ya think?)? It's still 18000 rounds testing God knows how many rifles (or barrels). The variance between rifles (barrels) should make it an even better proof (ya think?)? No, he (McMillan) doesn't say how many shot 9", and how many shot 6", and how many shot 3", BUT he does say they AVERAGED between 3"and 6". Might actually be a statement of the mode, I don't know. But I AM sure it doesn't matter.

Larry Gibson

05-02-2008, 08:57 PM

Ralf

You and leftiye just crack me up! To determine how something gets done or what is happening I deal with facts not notions , opinions or wild ass guesses. Look at the facts...look at what McMillan really said. Not what you think you wanted him to say. If the theory of bullets going to sleep is correct then your "proof" should have showed smaller groups at 600 yards (or somewhere in between) than at 100 yards. Even if we back track in 100 yard increments to 100 yards we will still see that the groups enlarged in a linear fashion. Your "proof" was supposed to be in answer to the challenge that groups do not get smaller as the range increases. In this case, your "proof", the groups do not get smaller. The groups in fact get larger. Also both you and leftiye insinuate the test involved 18,000 rounds. It did not. That was the "contract". It is very plain too discern that fact from McMillan's statement. However neither you nor leftiye seem adept at determining facts. Re-read Mcmillan's statement (his statement should have been quoted and seperated from you part Ralf) and if you can understand what is written you will then understand. If not then you are hopeless.

Leftiye

You might want to read carefully what is posted before shooting off your own mouth. I quite clearly stated "It’s just not a linear increase based on range increase." in the paragraph where I say "was a linear sized group". I also put it in bold, italicised print in the first post so you might understand it. Alas, you did not which should have been expected.

McMilan states; "never any larger than 6 inches as an average" He does not say "between 3 and 6". If 3" was the smallest (what he actually says) and some shot over 9" then the average would probably be around 6" as he states. He also seems to contradict himself with the word never in there. Perhaps you construed that to mean none of the groups were over 6". That however can not be as he goes on to talk about those that shot ove 9" groups. Obviously the 'average" was 6" groups. Makes sense to most of us except perhaps you. Again, look at the facts then try to make a comment that makes some sense.

McMillan also states; "We shot 18000 rounds of 50 cal ammo during a contract. The guns were sighted in and function tested at 100 yards and averaged 1.5 moa groups. When these same guns were tested at 600 yards you would expect the groups to run 1.5 moa or 9 inches."

That says the 18000 rounds were part of the "contract", not the test. Nowhwere does he state the 18000 rounds were all used in the test of zeroing at 100 and 600 yards. I'd bet this was a contract to train military snipers and not a "test" of his guns grouping abilities. Minimal ammo was used to sight in the rifle and then the rest was used during training. That is the usual course of events with this type of "contract".

Ralf

As a matter of fact I do work for the military. I contract to train Soldiers and Marines. I was gone to Alaska for 3 weeks last month and am leaving in the morning for North Carolina to do so again. Part of that training is weapons training. I probably will have a book out some day, just haven't had the time or the inclination to do it so far. Having a book published does not make you and expert BTW. There are lots of books published with lots of factual errors in them. I also do not claim to be an expert, just a man on a search for the way things happen. I do not have an answer for everything actually it is you and leftiye who seem to have all the answers. After all I am the one conducting a test to get answers, remember? It is you and leftiye who want to argue every point without looking at the results of my tests or coming up with test results of your own. I would even listen to bonafide test results of others but both or you fail to even provide those. I found McMillans "testsing of groups at 100 and 600 yards to be quite interesting but it in no way proved the concept, or even supported it, of bullets "going to sleep" and producing smaller groups at longer range than they do at shorter ranges. Perhaps the difference between us is I don't jump to conclusions or formulate answers based on preconcieved notions. I look at facts and the results of actual tests (and how those tests were conducted) to agree or disagree and to formulate my own ideas. I then use those facts to prove my ideas (or the ideas of others). You do not as once again you have only used the computer to search for something, anything that someone else might have done in an attempt to prove your own preconcieved notions. You have failed again. Unfortuneately, leftiye went down with you.

Larry Gibson

chaos

05-02-2008, 10:00 PM

Chaos, - I've gotta say it - your pen name coupled with that avatar really are kinda unsettling - But it's cool.

My Avitar is a picture of the little Inbreed who plays banjo in the greatest movie of all time...Deliverance

I was thinking of trading my baby Jesus in on a New and improved crying model. Its supposed to start crying when you are about to make a mistake. I could just put him up on my reloading bench and watch for the little tears. Then I wouldn't have to burdon myself with intellect such as this and then maybe my headache would go away.

runfiverun

05-02-2008, 10:12 PM

leftiye

05-02-2008, 11:06 PM

No conclusion to jump to Larry. That's been the conclusion ever since I first heard of it 30 years ago. Getting smaller groups at twice the distance, I mean. Bullets "going to sleep" is a fairly common occurrence, and a fairly universal conclusion for this type of experience.

Larry, you're unbelieveable! You can distort anything! Look at your guess that this was a training contract for snipers (a sniper rifle that only shoots 1.5 moa? Come on!) and you accept your guess without any substantiation. Wild @$$ed imagination! McMillan makes barrels, maybe the best in the world. He SAID that he was testing guns. If he had a contract, would it be training snipers? H@11 no! The military has it's schools for that.

There never was an actual experimental test in the McMillan scenario (as you try to manufacture). It was all production testing of guns for QC. It was data (facts) from that production.

Before you go off on your tangent about tests, I can no way accept the feeling you project that you think that anything that you don't like - even if everyone else on earth has seen it and knows what causes it - can be thrown out as common knowledge. There is no reason I can see to accept your opinions over the common knowledge - test or no test. It's hogwash.

Frankly, lately your arguments have been so bizarre that I can see that if you got turned to ashes by the facts, your teeth would say out of the pile of debris that nothing happened. You might win because everyone gives up on the process, but you'll still be wrong.

You're still grasping at straws.

blackthorn

05-03-2008, 11:40 AM

First let me say that any education beyond a partial grade 11 in the Canadian system is purely coincidental/accidental. I hold no degrees from any university (well known or otherwise). I am not a physicist, mathematician, etc. nor do I do my drinking in the library (as the wording (to one with my limited education) in some of the posts seem to indicate that some may do). I have read each and every contribution to this thread and I have found it to be sometimes confusing, sometimes frustrating, sometimes amusing and over all very informative. At this point, sans the final conclusions of Larry's testing, I am leaning toward a conclusion that when all is said and done we will likely decide that each firearm is different, each one has limits that are unique to that firearm, and that each firearm must be worked with to develop its full potential. At the end of these tests we should know (at least in Larry's rifles) whether there is an effect on accuracy caused by RPMs of varying degrees. In the end we will all draw our own conclusions based on our own experience and on our own individual rifles! I for one will wait until all the evidence is in before I attempt to draw my own conclusions. Test on Larry and thanks for your effort.

Tiger

05-03-2008, 11:56 AM

Larry

Read this from Paco: Lyman’s 3589, is the original mold number...not sure what it is today, probably something like 358009. But it is a round nose at around 280 grains in weight. I cast these bullets from magnum shotgun shot with 5% tin added...cast hot and dropped directly into water.

The ones I’m going to use for hunting I size and lube...then place them standing in water up to just above the shoulder and run the butane torch over the noses ...doesn’t take much...at the first sign of color change take the flame off...Let them cool slowly and the temper in the noses is gone for good expansion ...yet the body is hard and will take high pressure and velocity without fouling....pushing these from the 358 Winchester cartridge at 2400 fps is a snap with H335, AA 2015, or 3031...accuracy is very fine. Muzzle energy is almost 3600 lbs....a 30-06 has to work very hard to get even close to that kind of power.

Here the rifle he build for that amazing feat above: Using a commercial Mauser action, I had a 23 inch .358 barrel with a 1 in 10 twist mounted with a medium weight and taper....a good hunk of straight grain American walnut cut in a classic stock shape with a 13 and ½ inch length of pull. And it stayed a .358 Win until I ran into a BSA 24 inch rifle a few years later in .358 so I rechambered the custom rifle to 35 Whelen.

I wonder why he pick 10 twist. Maybe he not read Larrys test. Maybe this one man Larry doesn't know.

Here is the website for that Larry: http://www.leverguns.com/articles/paco/358_wcf.htm

Okay another:
Products

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Website: http://www.roosterlabs.com/products.html

I don't have to do the rpm figures. All those shooters out of Larrys threshold. I have come to conclusion too. I come to conclusion that Larry is little above average cast bullet shooter but when it come to high velocity cast bullet shooting he is of no use. He come up with threshold test to make his inadequate high velocity shooting abilities look better. Larry I can shoot high velocity and get good accuracy and I not doing series of tests to prove this to you or anyone else. You know how expensive gathering components have become in your area imagine what my costs are. I also think your lube and alloys not right. From reading I think one change you should make is use Bullshop Lube. I have to laugh maybe you try the Rooster Lube.

Your threshold test like TV commercials. You know what intelligence class they aimed at.

Ok Larry I await your negative reversal of my post contents. Yes I get little negative myself in dealing with you.

Ralf

Larry Gibson

05-03-2008, 02:44 PM

Leftiye

Larry, you're unbelieveable! You can distort anything! Look at your guess that this was a training contract for snipers (a sniper rifle that only shoots 1.5 moa? Come on!) and you accept your guess without any substantiation. Wild @$$ed imagination! McMillan makes barrels, maybe the best in the world. He SAID that he was testing guns. If he had a contract, would it be training snipers? H@11 no! The military has it's schools for that.

There never was an actual experimental test in the McMillan scenario (as you try to manufacture). It was all production testing of guns for QC. It was data (facts) from that production."

Again you make assumptions and statements of which you apparently know nothing. The military (ours) does indeed contract out sniper instruction. Especially when a unit procures a quanity of weapons such as the Barret. There are several models of barrets. The bolt actions give better accuracy against soft targets. Th semi auto barrets are intended to be used agains hard targets. You might check out the current issue of G&A. Also you're knowledge of sniper rifles is lacking. The M21 accuracy requirement was 2 MOA with M118, the M40 and M24s were 1.5 MOA. Tht's a fact Jack, check the manuals....oh, excuse me...facts are not what you pay attention to.

If you have "facts" as to what the "contract" was please post. Otherwise it's just more of your own misguided opinion.

However, the point was you and/or Ralf were challenged to provide proof that "(in your words from above post) That's been the conclusion ever since I first heard of it 30 years ago. Getting smaller groups at twice the distance, I mean. Bullets "going to sleep" is a fairly common occurrence, and a fairly universal conclusion for this type of experience". The mcMillan test as reported by Ralf do not substantiate "smaller groups at twice the distance". Thus the "proof" you and Ralf cite does not match the criteria of your own proof. You are both halucinating that it perhaps does. It does not.

Larry Gibson

Larry Gibson

05-03-2008, 02:49 PM

wow this is.........well.......come on you two......
just do a test.....? i cannot even add to that...
sept that my nice 100 yd loads in the 308 went to crap at 200 today. step down to 36
and bigger paper next time..

Maybe I won't have to run the test for Bass, seems you've got a running start on it. Keep us posted.

Larry Gibson

runfiverun

05-03-2008, 05:08 PM

larry
what i have been doing is almost a random range, lube test as in
pick a distance, a different distance each time, from 25 to 300 yds
and note temperature at that time and of the bbl and shoot for flyers and how many
untill groups come together. this is with a dry bbl andno cleaning in between sessions
so it is actually more then one at a time.

i am keeping notes and i have an awesome 50 yd load so far.
when i am done i am going to shoot my best 50yd best 100yd and best 200 yd
all at 300 yds.
under what i see as their best conditions fouler shots and ambient temps.
this is going to take at least a full year or more. i have started with 2000 cast boolits
cast from the same pot of mixed lead. [i made one 100lb pot of mix]
and one lot of 500 rem. 308 brass.
i am also trying to hold 100 loaded out to shoot test groups to see if lube builds up and
causes a loss of accuracy.
if i can finish this fall i will start with comparing all loads with a wet bbl between sessions.

it does look like i could just get me some zambini or that other lube though and just shoot 1/4"
groups ...well okay 1/2" groups all day..and save me a whole bunch of range time.

maybe i will just get some and have the guys just rub it on their cooper loads.

Larry Gibson

05-03-2008, 09:33 PM

blackthorn

Appreciate the thanks. When all is said and done ( i am testing in other calibers than .308 also) I believe whatever we find will hold. There is always a possibility of a rare exception but I believe upon close inspection we may find no exception. Remains to be seen though. Thanks again.

Larry Gibson

Larry Gibson

05-03-2008, 09:48 PM

Ralf

This may surprise you but the turnip truck you saw recently is not the one I fell off of. Do all the internet searches you want and come up with whoever you want (I have been reading Paco for years. I have one of his .22LR tools) It's not too hard to get "fine accuracy" out of 10" twist barrels with cast bullets at high velocity. If you have read read any of my posts regarding hunting loads you would know that. Cleaning the barrel every 3-5 shots usually allows you to push the RPM threshold for 3 shots. You might want to read more of Paco's writings and you'll discover that if you don't want to believe mine. Might be why I'm shooting 10 shot groups in my tests....to get by that and determine the continued accuracy capability.

You can find a whole litany of things gun writers and others "claim". I say, show me results not claims. When push comes to shove they can't. Ralf, do you shoot any cast bullets at all? Or are you just an armchair internet researcher interested in arguing a point? Why don't you back away from the computer and actually go shoot and chronograph (do you even have one?) some cast bullet tests and show us the results. Quoting other people's claims just does't cut it. I have posted the results of my test (so far more than 200 rounds). If you want to refute it come up with some actual tests. Gun writer and product manufacturers claims just aren't really worth much.

Larry Gibson

runfiverun

05-03-2008, 09:58 PM

larry
my 50 yd load is right near 33 grains and for some reason no filler my 100 load has no filler
either but i think my 200 load may be tamped in with lint .
i have a feeling each distance is going to require almost completely different components
except boolits and cases.
just the way it is looking at this point.
i am thinking near 2200 fps with h-322 for my 200 yd load. 12 twist.

405

05-03-2008, 11:24 PM

No, I haven't found the answer, no way I could do the testing, not good enough at it and don't understand it well enough to try :mrgreen:

But, not withstanding the McMillan statement which can either stand on it's own or be taken for what it is, it seems exactly this type of testing has been done (thought it had but just found a reference to it). Wish I had a copy of original reports! At the risk of getting jumped on..... here's a link to another forum's thread which was having almost the exact same debate. While it was not focusing on RPM theory or cast bullets it was following a similar line and debate about converging bullet paths. I found this quote of a quote to be fairly interesting and seemed to come from an objective source (not selling something :mrgreen:). The link is to a page in the forum thread and the quote of interest is at bottom of page. It references Army and NRA testing of bullet group dispersion at increasing distances. The reference quote of a quote seems almost boring in comparison to some of this. :coffee:

http://www.snipercentral.com/forums/viewtopic.php?t=13183&postdays=0&postorder=asc&start=45

waksupi

05-04-2008, 12:35 AM

As far as I can see, anyone involved in this topic, that isn't doing thier own empirical testing, don't have a dog in the fight. If you travel the internet, or read books, quoting other peoples writings, you do nothing to further a topic. Regardless of who the writer may be, they deserve to be questioned. I have certainly see many things in the NRA Cast Bullet book that are no longer viable ideas, so no longer hold it to be a final source. Same applies to Veral's writings.
THIS is where the cutting edge of cast bullets is. If you wish to be constructive, excellent. If you post just to inconvienience electrons upon your screen, your time may be better spent elsewhere.
If Tubbs, Gullo, or Munson say something about thier special areas of shooting, yes, I will pay attention, and try thier method. But, I will also try my own testing, to see if there is any other answer.
However, when you question and debate the one doing the research, you only forward the very thing we are here to dispell. This board has found the answer, solution, and fallacy of may things that have been thought to be gospel, for many years. If you are not willing to be part of the research, why participate? You contribute nothing by picking apart things which you have not researched yourself.
I guess what I am trying to say, be part of the solution to a question, rather than a road block.

Tiger

05-04-2008, 01:21 AM

Hallo Waksupi,

Hold for a moment. Take a look at what Larry wrote in his last post to me:

It's not too hard to get "fine accuracy" out of 10" twist barrels with cast bullets at high velocity. If you have read read any of my posts regarding hunting loads you would know that. Cleaning the barrel every 3-5 shots usually allows you to push the RPM threshold for 3 shots.

Larry read too. So now the test have changed. If the bore clean you can shoot the high velocity with accuracy in a fast twist barrel. First I say you keep adding things. Make up your mind. Next I say how can it be rpm ruins the accuracy above your threshold when you say can shoot 3 shots. Which is it Larry rpm or dirty bore that ruin accuracy?

Waksupi I have and have not done test. By that I mean I have shot and still shoot high velocity in fast twist barrels . What I do load my guns and take plane to United States and show everyone? I don't thinks so.

Larry one more question. Why Paco choose 10 twist for his custom rifle? He not talk to you about rpm threshold? Rules change now rpm ruin accuracy in fast twist barrel at high velocity only if many shots are taken.

All I can say be happy never to know the full potential of your rifles and cast bullets.

Ralf

runfiverun

05-04-2008, 02:14 AM

i believe the twist is a big part of the high vel problem
as much in the rpm [external]
as the internal ,stripping
you are also handicapping yourself to higher velocity with the faster twist
as you are expending more energy to rotate the boolit that could be used to push it forward.
and yes lube is a big part of what happens in the bbl too little or not used "properly"
in the bbl and leading occurs. [ leading is a good way to read a load and lube properties]
too much and accuracy suffers and you can cause leading this way also
" hydraulicing" causing the boolit to lose the rifling under the lube. extreme case.

now i have not heard larry say he has all the answers, what i have heard him say
is that he believes that cast boolits shoot to a higher level of accuracy
in a lower level of rpm,s
actually within a window between x and y and that above level y that accuracy
will be worse.
and so far as i can see he has not finished his tests but his testing so far
is pointing in this direction.
i am definately good at math, however i can see that his rifle with the same twist as
one that i have is exhibiting very similar traits as far as velocity and accuracy drop-off
if you are doing things differently and getting better results............
then please share your info.
even bass whom disagrees with larry at times put together some boolits
and shot them and posted what he did and his results some conclusions
were drawn and he was able to show what direction he was going with his discussion...

i have no idea what any of the numbers of larrys boolit molds look like
nor his mix of lead but we are using some similar components.
notice i was able to tell from his post about two different grain amounts
of powder just about what his results would be i have tried them as they are falling
in line with something i am working on.
it probably seems very haphazard from my earlier post but that is almost
the point to the test as this is how rifles are shot [ in the weather,rain,snow, hot ,cold,etc]
i am trying to replicate field conditions over a very long time in a short period
and am trying to do it in temp extremes, and notice distance accuracies
i.e. try to work up loads for distance [ best average for temp and weather extremes]
then compare them all at an untested distance. 300 yds for groups.

sorry this is so long.

Larry Gibson

05-04-2008, 07:02 AM

405

That is very interesting; would be interesting to se the actual results of that test. I'll quote what you point out here;

"Charles E Charles E is offline
Super Moderator

Join Date: Jul 2003
Location: Misplaced . . .
Posts: 1922
No, both the army and the NRA have done tests. They shot through multiple targets, so each shot printed on each target at different distances. Horizontal dispersion was constant in terms of MOA, vertical dispersion greater (again MOA) with distance, but within the amount of vertical you would expect given the velocity variations (this last was stated by the army, not me).

For people to come along & say the US Army & NRA are wrong, they need to show it. Not just "I shot so&so one day at 100 and such&such later at 200."

No ballistic theory I know of -- & this would include the years of testing by the Army at Aberdeen, uses the term "goes to sleep" or attributes increases in shot dispersion to small levels, say the difference between 4.5 degrees and 3.5 degrees, of coning motion. Moreover, coning motion is the sum of the fast arm and the slow arm; the fast arm damps, the slow arm grow slowly. Different rates of twist get you different amounts of fast & slow precession, but the sum varies only about a half to one degree.

We should keep an open mind, but what counts is constantly repeatable tests -- and the US Army has done a bunch of these. If you think brenchrest is demanding, consider the needs of artillery at 6000 yards."

It is also interesting to noe I am not the only one who uses this "litany"; "For people to come along & say the US Army & NRA are wrong, they need to show it. Not just "I shot so&so one day at 100 and such&such later at 200."

Many ballistics articles do discuss bullet yaw, pitch and wobble on exit from the muzzle and how this settels out in a short distance many times. They do not however, expouse any thoughts of bullets going to sleep and producing smaller groups at longer ranges than at shorter ranges. I do think it has been done as I have pretty much equaled group sizes at 100 and 200 yards myself. But it is an anomoly and not readily (if ever) reproduceable.

Thanks for the input 405.

Larry Gibson

Larry Gibson

05-04-2008, 07:17 AM

Ralf

First of all go back and research my posts concerning hunting accuracy. I quoted the term "fine accuracy" because I do not take it to mean "exceptional accurate" or the "best obtainable accuracy", etc. "Fine accuracy" for a hunting rifle (what Paco was talking about) can be as much as 6 moa to those who only shoot at close range. Many accept 2-3" groups at 50 yards as "fine accuracy". How many moa are they?

The question has not changed, the test has not changed.

I'll assume Paco chose the 10" barrel because when he built that rifle (just when do you think it was Ralf? He built that rifle a long time ago.) the 10" was considered "necessary" for heavy bullets of 35 caiber. Paco did not talk to me becuase when he built the rifle cast bullet inaccuracy was still though to be a function of pressure. The topic of RPM causing the inaccuracy above a certain level was not a concept back then.

Do some of your own testing, you may really learn something. At least go shooting, it may relieve some of your frustration. You then may have something to quote of your own instead of others.

Larry Gibson

Larry Gibson

05-04-2008, 07:20 AM

Runfiverrun

Keep up the testing, thats how we learn. Keep posting here, that's how we all learn.

Larry Gibson

Tiger

05-04-2008, 11:23 AM

Larry

You should be politician campaign director. You avoid issues and certain questions. Answer to why you can shoot up to 3 shots high velocity fast twist accurately then it go bad. If it can do that why you say rpm have a threshold? You fell into something as you lay in it you do not recognize it.
Bore fouling part the reason to not achieve accuracy at high velocity with both fast or slow twist. More so with fast twist.

Like I tell Waksupi I have done all this. What you suggest I take holidays from work and come visit?

Ralf

leftiye

05-04-2008, 12:02 PM

Ralf, No it's just a ploy to help Larry avoid having to answer questions about concepts. What percentage of our members have ever performed an experiment other than "I made a load, and it shot like this"? What percentage of the posts on this forum or any other forums involve anything more than "I did so and so, and X happened. What's going on?" But now all of a sudden with Larry, virtually nothing in God's green earth is valid except what Larry wants to hear. ALWAYS followed by the "do a test" dodge.

Larry can quote text from other forums, we can't. Somebody quoting the Army is okay, it supports Larry's position. Somebody quoting (not paraphrasing) Gale McMillan doesn't get the time of day. The cutting edge isn't the Army (1 1/2 moa sniper rifles remember - Do you believe that?), it's the bench rest and industrial people (.2 moa sniper rifles) like Gale. Plainly.

Of course, when you DO quote anything that amounts to being able to prove anything, It's never good enough to matter (look at the history of this thread). So why waste your time doing a test so that Larry will supposedly address your information conscientiously. THAT hasn't happened yet.

It goes this way. Step 1 - Read post. Don't like it. Distort it. Step 2 address the issue created by your distortion (not what was said). Step 3 - (oatmeal) - Deliver long spiel about what was profferred not being acceptable because there was no test data. Babble on about how author didn't read Larry's test format and/or results. Or just quote larry's test directly ad infinitum. Step four - Attack author personally. His comments are stupid, His comments are inintelligent, He isn't very good at scientific things, He's stupid, He's obnoxious.

If this forum isn't a place for discussion of concepts and issues by the proper rules of addressing issues, Then I for one will not just refrain from argueing with Larry, I'll refrain from coming to this site. It will then have no interest for me. If whatever is said is going to be screened by a biased party as to whether or not he wants to hear it or not, then let him waste HIS time, not mine.

Tiger

05-04-2008, 01:29 PM

Leftiye

You forget next step. It now become forum law that you can not disagree without having done tests.

In big business they have meeting people sit around table to solve problems. People throw out ideas and they call this brainstorming. Can not do that here, must do tests. Some good Mcmillan tests do he fire 18000 rounds and Larry don't like. So who going believe Ralf over other side of pond?

Ralf

leftiye

05-04-2008, 01:35 PM

So who going believe Ralf over other side of pond?

Not Larry for sure. Don't feel bad, there are a lot of people here who agree with you!

leftiye

05-04-2008, 01:59 PM

"They do not however, expouse any thoughts of bullets going to sleep and producing smaller groups at longer ranges than at shorter ranges. I do think it has been done as I have pretty much equaled group sizes at 100 and 200 yards myself. But it is an anomoly and not readily (if ever) reproduceable." Larry gibson

Larry, hold on to your seat - I agree with you on this. Not the part about some "experts" (if you can do that, then I can too?) not espousing smaller groups at longer range, etc..

But I agree it does happen. It happens when all of the same shots pass through several targets at each of several distances too. No parallax happening there. I agree that it is not readily produceable - and I have myelf have never tried to produce it. The bad thing about the xxperts on that other board and other places saying it doesn't happen is that a couple of posts later there is another poster saying that it happened to him again today. One of the posts there was about an interview with a 1000 yd. benchrest shooter of some repute whose groups are often .2 moa saying that it happened often to him in his testing. I guess we choose who to believe on which days, huh?

My point is that the recurrence of this over and over for 30 years to me indicates that something is actually happening, regardless of who doesn't want to believe it. There are many many incidences.

Larry Gibson

05-04-2008, 02:38 PM

Ralf

"Answer to why you can shoot up to 3 shots high velocity fast twist accurately then it go bad."

RPM

"If it can do that why you say rpm have a threshold?"

Because before the accuracy goes at a level of velocity accuracy is good and consistant for a large number of rounds without cleaning the barrel.

"You fell into something as you lay in it you do not recognize it."

Don't you wish!

"Bore fouling part the reason to not achieve accuracy at high velocity with both fast or slow twist. More so with fast twist."

Duh...if you'ld pay attention to what I write instead of your own preconcieved conclusions you'ld know that is what I say. It is the imbalances caused during casting, sizing and accelleration that the RPM acts upon during flight. This is what creates the inaccuracy. Normally the increase of inaccuracy is linear. However at a certain level with regular cast bullets the inaccuracy is not linear but in a much greater fashion. That is the area of the RPM threshold I believe. The tests will prove or disprove it. How may times must you be told this?

"Like I tell Waksupi I have done all this. What you suggest I take holidays from work and come visit?"

If you have done this the show us the targets, the loads, the rifle, and the velocity. You do not have to come over here to do it. However if you'ld like to you would be welcome.

Larry Gibson

Tiger

05-04-2008, 03:10 PM

Larry you say:Duh...if you'ld pay attention to what I write instead of your own preconcieved conclusions you'ld know that is what I say. It is the imbalances caused during casting, sizing and accelleration that the RPM acts upon during flight. This is what creates the inaccuracy. Normally the increase of inaccuracy is linear. However at a certain level with regular cast bullets the inaccuracy is not linear but in a much greater fashion. That is the area of the RPM threshold I believe. The tests will prove or disprove it. How may times must you be told this?

It is more then that. Bad casting wrong powder choice wrong alloy bad lube
wrong bullet sizing wrong fitting bullet to throat load techniques case neck fit to neck in chamber bullet tension gas check situation and more. Throw in too mechanical problems with rifle like bad bedding you know the stuff I am sure. If one can shoot high velocity high rpm for certain amount time before accuracy go away it is not rpm causing problem. Look to the area of black powder. One big problem with this powder is fouling. You almost say with your test that it should read fouling threshold.

Ralf

leftiye

05-04-2008, 05:46 PM

"Duh...if you'ld pay attention to what I write instead of your own preconcieved conclusions you'ld know that is what I say. It is the imbalances caused during casting, sizing and accelleration that the RPM acts upon during flight. This is what creates the inaccuracy. Normally the increase of inaccuracy is linear. However at a certain level with regular cast bullets the inaccuracy is not linear but in a much greater fashion. That is the area of the RPM threshold I believe. The tests will prove or disprove it. How may times must you be told this?" Larry Gibson

First off, remember a while back when you "weren't admitting anything" in response to my statement that you had said that RPM needed an imbalance or distortion to work on. 'Twould be easier on both of us if a stretched string scribed a straight line. Why not admit it?

And continuing in that vein, and going way back, virtually all of your detractors at one time or another stipulated that RPM does have an effect, just not maybe the supreme effect you wanted to hear admitted. What's the diff? Even if Rpm does have more effect than I think it will; we'll all - even yourself - continue to do what we've always done to overcome inaccuracy, at high velocity.

BTW, How do you see RPMs causing spiral boolit paths without deflection from "footballing" (yawing) against air resistance being the operant force? I've got to say that pure out of balance alone that is large enough to throw the boolit from side to side is more likely to simply produce tumbling boolits that depart to parts unknown than spiral paths. Nor will out of balance very often allow the boolit to continue to fly point on. Only in the rare instances that the defect in balance is at the centerline of or balanced across the centerline of the weight of the boolit. And you COULD HAVE forgone the Duh - maybe?

runfiverun

05-04-2008, 06:43 PM

normally the increase of innacuracy is linear 1"@100, 2"@ 200 and so on
up to a point !!! this is and has been the consensus amongst shooters, testers and ballisticians.
for a number of years words like you should get. and i once saw.
were good enough for readers and debates around the camp.
then came a thing called a chronograph. not the one on a chain with a big box on the end.
and rifle scopes that you could see the moon with [both sides]
and suddenly the 300 win mag was really an overbored 30-06 not doing what
THEY said it was doing sooooo. you say whats that got to do with this thread?
it made the factories prove what their boxes were saying on the back side.
you wanna sell ammo make it right,cause the other guy is gonna do it. guess who
makes the profit?
i can feel larrys frustration with you two and i think you do not READ his posts
just skim them and look for things to peck and poke at. [kinda like a retired mother in law]

my god i am about dim and i can see what larry is saying plain as day
and i know you two guys can also,
if you are doing
iv'e already said this.............enough.

leftiye

05-04-2008, 07:20 PM

R5R,
You're right, I think we all know very well what Larry is trying to prove. More often than not when we get the rehash of Larry's test, it is when we should be hearing a rebuttal to something stated, or an answer to a question.

I spent four hours going through this thread last night with a friend. For my money, I do read Larry's posts. Time after time I read him throwing some off the wall distortion (or something completely off subject) at me in response to something I asked him. This is not how it is supposed to happen. Yes, one might tend to ignore those kinds of answers. Especially when they totally beg the question asked or the point someone was attempting to make..

Larry doesn't ask me to explain something that is a fact that opposes my viewpoint (as I do him), he uses his imagination to turn what I DID ask him that DOES throw HIS ideas into question into something else completely. And in doing so he escapes answering my questions, and rebutting my statements.

And, yes it is a waste of all of our times.

runfiverun

05-04-2008, 10:10 PM

well you all could cut him a it of slack.
if he is like me when i get on a project i tend to focus fully on it [tunnel vision]
and you probably can tell from some of my posts a bit scattered on other subjects.
even if they are similar or even on a parallel line like the bass test i need to go and re-read
it i may have done his test and and have some notes on it, but glossily didnot let it
sink in .
larry pointed out the similarities earlier but i focus too narrowly and what would a few more rounds i was going to shoot any way hurt?

runfiverun

05-04-2008, 10:32 PM

Larry Gibson

05-05-2008, 05:18 AM

larry
if the test of bass's is the one on page 18
i am not really sure of what he wants, it looks to me he wants to shoot a bad
load at distance to see if it gets worse?
if the last load taken from 1to 200 yds is an indication of worse.
i would literally have to find a barn to shoot at 300 yds.
when i said that load went at 200 it went ,out of ten shots 4 were on paper.

Runfiverun

Regards Bass's test; there can be a difference between a "bad" load and a load that is shooting badly in the RPM threshold. This is something that Ralf has a hard time comprehending if you see his last post. All of the things he is talking about do not apply in this test. While I do not say I cast a perfect bullet (who really does?) the bullets and loads for this test are good. The rifles are good rifles with a track record of accuracy using both cast and jacketed bullets. They are shooting some of the cast bullet loads during this test with very good accuracy. That is the point that Ralf and perhaps leftiye seem to not understand. These are good loads and these are good rifles.

What I am doing with these good loads and good rifles is to merely increase velocity up to 2500+/- fps observing when accuracy lessons. I am measuring the size of the groups and a multitude of other things with the M43. This gives me comparative data to make observations.

So, when Bass mentioned his latest test I believe he wants me to shoot groups with a load that is in or above the RPM threshold and “shooting badly”. This test is to determine whether or not the inaccuracy is caused from the load/rifle being bad or whether it is caused by RPM. The measured BCs do not indicate there is increased distortion of the bullet nor that the bullets has excessive wobble, yaw or pitch and is becoming unstable. If the load/rifle is bad (nodes, bad bullets, uneven bases, bad crown, etc) then the groups should still open up when fired at 50, 100 and 200 yards in a linear fashion comparable to moa’s (i.e. 1” at 50, 2” at 100 and 4” at 200). If it is RPM that is causing the inaccuracy then the increase in group size will be larger than linear as the range increases (i.e. 1” at 50. 2” at 100 and 6” at 200 yards). This is because the RPM does not slow down significantly during a bullets flight and as range increases the centrifugal force of the RPM will have a greater effect on the flight of the bullet.

I concur with Bass that this is what should occur and should amply demonstrate if it is RPM. It will not establish the fact of an RPM threshold but it will establish the root cause of the inaccuracy.

Larry Gibson

Bass Ackward

05-05-2008, 07:00 AM

I concur with Bass that this is what should occur and should amply demonstrate if it is RPM. It will not establish the fact of an RPM threshold but it will establish the root cause of the inaccuracy. Larry Gibson

If a person is serious about developing a high velocity load, the important point is to correctly identify problems and fight the battle that needs fought.

Larry should use the same top end loads that he did in this test that the slow twist performed better than the fast. Keep this simple. We know that the slower twist is going to shoot these more accurately, he already proved that. Right now we are drawing the conclusion that it is RPMS that is the reason.

If groups are radically bigger with the faster twist rate at 200 than they were at 100, then Larry has proven the RPM theory. If the groups from all twist rates are all linear, then RPMs was NOT the reason for the inaccuracy.

Let's identify the enemy that needs fought.

Added: Really Larry only has to do this with the 10 twist at first. It should be the WORST of the three twist rates. If it is wild, then he has satisfied me and he can continue with the other twists if he wants. If the 10 twist is poor, but still linear, then why waste his time and components? Cause RPMs won't be the problem.

Larry Gibson

05-05-2008, 07:26 AM

If a person is serious about developing a high velocity load, the important point is to correctly identify problems and fight the battle that needs fought.

Larry should use the same top end loads that he did in this test that the slow twist performed better than the fast. Keep this simple. We know that the slower twist is going to shoot these more accurately, he already proved that. Right now we are drawing the conclusion that it is RPMS that is the reason.

If groups are radically bigger with the faster twist rate at 200 than they were at 100, then Larry has proven the RPM theory. If the groups from all twist rates are all linear, then RPMs was NOT the reason for the inaccuracy.

Let's identify the enemy that needs fought.

Added: Really Larry only has to do this with the 10 twist at first. It should be the WORST of the three twist rates. If it is wild, then he has satisfied me and he can continue with the other twists if he wants. If the 10 twist is poor, but still linear, then why waste his time and components? Cause RPMs won't be the problem.

I concur with Bass (don't be shocked folks, Bass and I agree quite a bit actually) and that's exactly what I shall do. Hope to get it accomplished between 12-18 May.

Larry Gibson

runfiverun

05-05-2008, 10:33 AM

if my notes and shooting are correct
my ruger 308 has a 1-10 twist it has a conditioned bore
and i should have 60-80 rounds of culled 165 rcbs silh w- g/c loaded with
37 gr imr 4895, fed 210 primer in rem cases that have been trimmed,flash holes done
and primer pockets cut to depth.
just a plain average everyday cast load, this should be right at the edge of the rpm
scale.
i donot have a big nor fancy scope on this rifle but i think it will shoot to 200 yds well
enough.
i took a deer with it at near this distance, and can hit the rams on the 200meter
silhouette range standing so if i have some weather windows i think i will try
this out this week this week.

Tiger

05-05-2008, 01:07 PM

Larry say: The rifles are good rifles with a track record of accuracy using both cast and jacketed bullets. They are shooting some of the cast bullet loads during this test with very good accuracy. That is the point that Ralf and perhaps leftiye seem to not understand. These are good loads and these are good rifles.

I will say one thing for you Larry what is word..Bravito ... perhaps spelling wrong but you get point. You certainly have no threshold when it come to talking about yourself and shooting ability.

Ralf understand quite well. I hate to see such knowledge and good cast shooter such as Bass fall to your constant rpm bs.

Ralf

Tiger

05-05-2008, 02:53 PM

Larry

I was thinking back some search I have done. It was the mountain mold mans contest. His requirement beside rpm to be more exact. I think he say no cleaning of the bore during the shooting. I think he know something he not say. He know something of fouling.

Larry maybe you right I do not know what you say sometimes. More to point about you say you can shoot up to 3 shots or more high velocity high rpm before accuracy go bad because fouling. I still don't think you explain the mechanics of that to me that it sink in. Let me take stab with the good old tire story. Say tire is balanced well . Then say you get some mud or maybe better some tar stuck to tire. You and I know this unbalance tire. Think this as fouling. Then I say the diameter of tire not change. Think this as twist. Tell me again how rpm has to do with bad accuracy after bore becomes fouled when twist was fine when bore clean.

I know I tax you patience and for that I say I am sorry. Please explain more about above.

Ralf

Tiger

05-05-2008, 03:39 PM

Larry Gibson

05-05-2008, 07:01 PM

Ralf

“Bravito”, so ok you don’t spell very well. Also your English is somewhat broken to say the least. I don’t have a problem with that which is why I am having patience with you. I don’t know where you are but obviously English is a second language. That is probably why I also repeat numerous points to you. That is really not a problem with me. It can be a little annoying but we’ll work past that.

I normally don’t beat my own chest with my own “bravito” when it comes to my shooting skills. I normally just like to stick with shooting facts. I’ll give you a little of my back ground and you can judge for yourself whether or not I have any shooting skills or am just blowing "bravito".

I began with smallbore competition when I was 16 years old. I had been shooting and hunting since I was 5 years old (I am 61 years old now). I joined the Army when I was 17 and as an infantryman I qualified expert with the M14, the M1911A1, the M14E2, The M60 MG, the M79 and the bayonet during training. I went to war when I was 18 years old as an airborne infantry scout (obviously had something going as I am here typing this today) I qualified Expert every year with either the M14 or M16 for the 42 years I was in the Army. Besides being an infantryman I also spent 26 years as a Special Forces NCO, most of them as a Special Forces Weapons NCO. I spent a lot of time all over the world teaching our Solders/Marines and those of other nations how to shoot with proper marksmanship skills. I am sniper trained and have given instruction to Rangers and Special Forces. I have served in two wars and a lot of small sh*th*les throught the world in hostile environments. I literally have the “chest full of medals” both from war and peace to demonstrate how good I was/am.

Some of the time in the Army was reserve and National Guard time so for my civilian occupation I managed a gun department in a major sporting good store, repaired guns and studied firearms with a passion. I also was a police officer for 18 years and during that time I was a state certified Advanced Firearms Instructor for the state board on police standards and training. I provided some years of instruction to the police officers in a tri-county area.

I have a Master Classification in both High Power and Long Range from the NRA earned with an M14 Service Rifle. I was a Class A IPSC competitor some years back and also heavily competed in police matches. I also was a state sniper rifle champion and a state assault rifle champion during statewide police competitions. I have hunted across North America including Alaska, in Central America and Asia. I have a Rocky Mountain Bighorn Sheep in my living room that scores a paltry 188 7/8ths SCI among other mounts.

There are probably a few more things but I think you may get the idea on my shooting ability. Oh yeah, one more thing; I have been shooting cast bullets since I was 15 and have been casting my own since I was 20.

Any other questions on this "bravito" point?

Larry Gibson

Larry Gibson

05-05-2008, 07:15 PM

Ralf

"Larry maybe you right I do not know what you say sometimes. More to point about you say you can shoot up to 3 shots or more high velocity high rpm before accuracy go bad because fouling. I still don't think you explain the mechanics of that to me that it sink in. Let me take stab with the good old tire story. Say tire is balanced well . Then say you get some mud or maybe better some tar stuck to tire. You and I know this unbalance tire. Think this as fouling."

You are correct, it is fouling and with fouling comes increased deformation of the bullet during accelleration. I believe I've mentioned this to you numerous times.

"Then I say the diameter of tire not change. Think this as twist. Tell me again how rpm has to do with bad accuracy after bore becomes fouled when twist was fine when bore clean."

The diameter of the tire may not change but perhaps the air pressure in the tire is less and it doesn't roll as smoothly as it did before. Think of the air getting let out of the tire as what happenss to the bullet during accelleration (internal balistics). Think of the tire rolling as what happens to the bullet during flight (external ballistics). It is during external ballistics (the flight of the bullet) where the RPM adversely affects the accuracy. I believe I've also mentioned this numerous times to you also.

You really need to start thinking of what is happening to the bullet in flight instead of in the barrel.

Larry Gibson

Larry Gibson

05-05-2008, 07:24 PM

Larry

How about this then Larry. Shoot as many shots you can through fast twist at high velocity then clean and shoot same number as before and continue to do like. So then we end up with good accuracy group. How you then pin blame on rpm and make up threshold? Yes I am confused.

Hang in here with last post my. I sure you can explain.

Ralf

Yes Ralf, you are confused. I don't mean that in a sarcastic way either. I really mean you are confued. Let's accept what happens to the bullet inside the barrel. The bullet gets unbalanced, ok. So let's then look at what is happening this unbalanced bullet during flight. RPM is causing it to be inaccurate. Maybe by only a slight degree but still inaccurate. Rotaional stability is what is still keeping it fairly accurate. However if we increase the RPM to this cast bullet there is a point where accuracy will radically decrease. This is that bullets RPM threshold. Thus you can see in the test with the 10" twist accuracy was pretty good up through 1900 or so fps (I don't have the figures here with me to quote exactly) after that accuracy went very bad very quickly as velocity/RPM was increased. Those are the facts of the test.

As to leading Bass down a path to BS? I know Bass and I don't think BS will do it. If he is convinced of the RPMs adverse effect on cast bullet accuracy, as we are discussing, it will be because the facts have convinced him, not me.

Larry Gibson

runfiverun

05-05-2008, 07:55 PM

tiger you should not need to clean a good load, i am over 200 rounds without loss
of accuracy and no type of cleaning.
refer to earlier post...
however i still have "firstshot" flyers. and if you are going to only shoot a few rounds
and clean a bbl to get high velocity you can keep that...... [ i know,, the high priceof fame]
but how can you know the potential of a cast load if by the time it settles in you gotta clean it
and start over.....
the flyer thing i will be working on later after the fouling thing i'm doing now.

Pat I.

05-05-2008, 11:13 PM

Ralf

“Bravito”, so ok you don’t spell very well. Also your English is somewhat broken to say the least. I don’t have a problem with that which is why I am having patience with you.Larry Gibson

Larry,

And if you check his earlier posts it's getting more broken by the minute. This cat's just pullin your chain :kidding:.

Larry Gibson

05-06-2008, 12:55 AM

Larry,

And if you check his earlier posts it's getting more broken by the minute. This cat's just pullin your chain :kidding:.

Yes, I've considered that but I like to give everyone here the benifit of the doubt. If he is doing that then He'll be forever called to task for it here and nothing he might have to say in the future will be meaningful.

Larry Gibson

Tiger

05-06-2008, 01:45 AM

Larry,

Okay Larry I like the last you posted to me. Here is what I think. Could we say that your rpm threshold is one without have to clean the bore often?
Could we say to that the fouling damage bullet and rpm then act upon it?
Can we agree this two things?

Okay I don't know what problem here is. First onceabull then this Pat I.

I think with few arguments we get along but these other two I don't know.

Larry I live Frankfurt Germany. With explanation your military service I bet you where at one time another in bases here. Right? Which if so?

Okay back to rpm. When will you finish last test? Will you try test with other calibers?

Ralf

Larry Gibson

05-06-2008, 03:51 AM

Ralf

Okay Larry I like the last you posted to me. Here is what I think. Could we say that your rpm threshold is one without have to clean the bore often?
Could we say to that the fouling damage bullet and rpm then act upon it?
Can we agree this two things?

Agree on it? Heck Ralf, that's what I've been trying to tell you from the beginning! Looks like we're on the same page of the hymn book after all. The RPM threshold will happen whther you clean the bore or not. It'sjust that if you aren't pushing the threshold too hard the first 3-5 shots out of a clean bore will give reasonable (note I said "reasonable") hunting accuracy. Not the best ccuracy but reasonable hunring accuracy. Then if the barrel is not cleaned the accuacy can get pretty bad.

Larry I live Frankfurt Germany. With explanation your military service I bet you where at one time another in bases here. Right? Which if so?

I traveled through there but most of my time except for the middle east was in the aisian or central American theaters.

Okay back to rpm. When will you finish last test? Will you try test with other calibers?

Yes, I have mentioned that when I'm done with the 3 twists in .308W I will test regular cast bullets in the following rifles with there standard twists; .223 (9" & 12"), 6.5 Swede (7.5"), 7x57 Mauser (9.5"), 30-06 (10"), 303 British (10"0, 7.65 Argentine (9.5"), 7.62x54R (9.5"), 8x57 (9.5"and 375 H&H (12"). All will be tested with the M43 Oehler wilth groups at 100 yards.

Larry Gibson

Bass Ackward

05-06-2008, 06:46 AM

Ralf,

As bullet speed increases, the ability to pass fouling acts more and more like an obstacle. This obstacle would eventually require the barrel to bulge or the bullet to size down. Lead sizes down.

We all know what undersized bullets shoot like at any RPM level. Fouling is in effect creating lube fliers (undersized bullets) with each shot that dramatically open groups to look like RPMs. The more muzzle pressure you have when this happens, the wilder groups get. That's why I believe the slower twist shows better accuracy cause when you size down, you are in effect lowering rifling height by lowering the grip on the bullet and the slower twist angle of the rifling can maintain a grip on it for a better launch.

Same effect you see down low if your barrel leads up. Groups open fast, but you don't call it RPMs there. Bullet HAS to get passed that somehow and the bullet pays the price. Fouling is fouling, but velocity increases the effect. The faster you go, the more sizing takes place just like a tire hydroplaning on a wet road if you go fast enough .... or if you have enough water.

A wise man here once said, "the best accuracy occurs just before leading begins". That is because lube is used up and a balance is achieved. It's just more difficult to do that at higher velocities. This is a big problem for me and softer lead at higher velocities, especially in cold weather. Over 80 degrees one load is MOA all day long. By 50 degrees, that load is a 5"er.

There are many more factors that are tweakers to accuracy, but if your groups are linear and BAD, I'd say 99% chance this is what killed your accuracy. Pressure escaping unevenly around an undersized slug caused more wobble. Down low in velocity or with calibers that have ultra slow twist rates, you would key hole. Only high RPMs saves you from seeing that. But at the same time, it hides the true cause making it look like RPMs. The only cure is a harder bullet, less or better lube and clean the bore. Or .... a barrel with taller rifling for lead. :grin:

You can't test for this, only eliminate RPMs as the cause using linearity as a guide. If your groups are linear, this is the first place I look.

Pat I.

05-06-2008, 08:11 AM

Larry,

Okay I don't know what problem here is. First onceabull then this Pat I.

Ralf

Maybe we just have good BS detectors. Let's take a random paragraph from your post #134

" Larry it's not the rpm. One other thing you haven't looked at is that shooting at very high velocity increased the recoil. Take the 30-06 with a twist of 10 and lets use the Lyman 311284 or the Lyman 311299. Both of these bullets are over 200 grains. In order to get them out of Larry Gibson's rpm range on the high side requires what I think is a very high velocity which is going to have much more recoil then a bullet that is lighter and shot within Larry's rpm range for accuracy. I will tell you where I am going with this. None of you here will dispute that a shooter can shoot more accurate with a rifle that doesn't have a lot of recoil. In order to prove Larry's theory a rifle would have to be fixed in a solid firing device that would take all the human error out of the testing."

Now on to post #433.

" I was thinking back some search I have done. It was the mountain mold mans contest. His requirement beside rpm to be more exact. I think he say no cleaning of the bore during the shooting. I think he know something he not say. He know something of fouling."

Not to be insulting but Tonto couldn't have said the second post better. Just a gut feeling but you don't have a 6.5 Grendel do you?

this Pat I.

Tiger

05-06-2008, 01:51 PM

Larry

I look forward to other caliber test. I have some calibers you listed.

By way I look up bravito on google and I get a good laugh. So I find out the word is bravado. I chop that one up good hey?

Pat I

I struggle with the english but you prefer I will from now use microsoft word?

No I do not have 6.5 grendel do you? I do have 6.5x47 Lapua. From what I research seem many members have trouble with the 6.5 caliber here. Maybe Larry can help them with this.

Ralf

leftiye

05-06-2008, 01:55 PM

Pat,
"Maybe we just have good B.S. detectors" OR maybe you're just wrong. And insulting. But that's standard on this thread. Why not though eh? Only half the posts here address issues anyway. The other half are mouthwash (might as well be gargleing).

Ralf, "Bravito" actually says it better! Really.

45 2.1

05-06-2008, 02:11 PM

Larry Gibson

05-06-2008, 02:50 PM

From what I research seem many members have trouble with the 6.5 caliber here. Maybe Larry can help them with this.

Ralf, I don't really believe thats gonna happen as thats out of Larry's range and ability right now.

My, my but isn't that snippy!

As it seems you can't read and comprehend at the same time (I can be snippy too!) let me explain; The test of further cartridge/calibers, the 6.5 Swede being one I mentioned, as Ralf requested will not be to develop a most accurate load as you seem to continuously p*ss and moan about. Nor will it be to help anyone here. It will be merely to demonstrate if the RPM threshold adversely affects the 6.5 and if so, then at what velocity/RPM (with the rifle/bullet/load used) does it hit the RPM threshold. That may assist some here but that is not the intent. It is the same though as is the intent of this test and that is not to develop a most accurate load for any of the 3 different twist rifles used. A fact you seem not able to comprehend.

Thanks for your "valuable" contribution to this discussion.

Larry Gibson

45 2.1

05-06-2008, 02:59 PM

My, my but isn't that snippy!

As it seems you can't read and comprehend at the same time (I can be snippy too!) let me explain; The test of further cartridge/calibers, the 6.5 Swede being one I mentioned, as Ralf requested will not be to develop a most accurate load as you seem to continuously p*ss and moan about. Nor will it be to help anyone here. It will be merely to demonstrate if the RPM threshold adversely affects the 6.5 and if so, then at what velocity/RPM (with the rifle/bullet/load used) does it hit the RPM threshold. That may assist some here but that is not the intent. It is the same though as is the intent of this test and that is not to develop a most accurate load for any of the 3 different twist rifles used. A fact you seem not able to comprehend.

Thanks for your "valuable" contribution to this discussion.

Larry Gibson

You yourself have continuously denegrated anyone who disagreed with you on several threads. You have also said that excellent accuracy cannot be achieved via your RPM statements at those levels. Now you are having a fit..... go cool off and make a tactfull response when you can regain some rationality if you are at all capable of doing that.

Tiger

05-06-2008, 03:25 PM

45 2.1

05-06-2008, 03:53 PM

My, my; now isn't that snippy!

Larry Gibson

Larry pulled his post preceding this one. Embarassment it seems.

Somewhat better, but still not tactfull. Anyway, I congratulate you on your return of composure. Thats not at all snippy compared to what could be said using your own statements in rebuttal.

leftiye

05-06-2008, 03:53 PM

larry,

"You yourself have continuously denegrated anyone who disagreed with you on several threads." 45 2.1

45 2.1, WELL said! In both cases. Don't forget, Larry can't comprehend rebuttals (or chooses not to).

Larry Gibson

05-06-2008, 03:54 PM

Oh oh I guess this stuff with onceabull and Pat I open can of worms. I am sorry if I provoked that.

Larry first I say there is a six hour difference between us and makes it difficult to be on same times. I want to ask you think it just 6.5 caliber that causes problem or the Swede in general? Is it more the fast twist in that caliber? I do not see much talk about other 6.5 calibers much beside Swede. I have not shot cast out of my 6.5x47 yet. While on cast it is I think harder to get suitable material for alloy here. I am afraid wheelweights going to be past history everywhere soon. Even the militaries change bullet composition.

Ralf

Ralf

Apparently they don't believe you are in Germany, they may think you are an old member (barred from site) named Starmetal. Seems they are trying to smoke you out. Six hours if I'm on the east coast or 8 hours if I'm on the west coast. Either way you've got a running start on "happy hour" on me. That's ok because you pass out before I do! Just kidding.

With the 6.5 Swede it is also the RPM threshold (I've stated this before for a long time so no sense saying something else now). The faster twist generates high RPM a lot sooner so best accuracy isusually down in the 1500 fps range or so. Having corresponded by PM on this with 45 2.1 I've found we both can push the RPM threshold up into the 1800 fps range and maintain a fair degree of accuracy. Not the best the rifle is capable of but pretty fair. Takes a lot of tweaking and can get kind of more anal than some want but it can be done. $5 2.1 claims I can't do it. He is wrong.

I'm always glad to help anyone on this forum whether 45 2.1 thinks I can or not.

Larry Gibson

Larry Gibson

05-06-2008, 04:11 PM

45 2.1

I'm not the one having a fit here. Speaking of not tactfull; telling me where to go and what do is definately not being tactfull. You make a denegrating statement of my abilities and then chastise me, get serious. You can't handle the heat in this discussion stay out of the kitchen.

Larry Gibson

leftiye

05-06-2008, 05:12 PM

The devil is the only one enjoying the heat in hell.

45 2.1

05-07-2008, 06:42 AM

With the 6.5 Swede it is also the RPM threshold (I've stated this before for a long time so no sense saying something else now). The faster twist generates high RPM a lot sooner so best accuracy isusually down in the 1500 fps range or so. Having corresponded by PM on this with 45 2.1 Very old news with a handfull of PMs total. At the time you were with the 1600 fps crowd. Anyone can do the 1800 fps with a little instruction. Its the velocities above 1800 fps that most flunk at, including you it seems from your writings. I've found we both can push the RPM threshold up into the 1800 fps range and maintain a fair degree of accuracy. Not the best the rifle is capable of but pretty fair. Under MOA at 1800 fps is pretty fair considering your the guy who isn't taking accuracy into consideration on these RPM threads. It's a rifle, not a musket. Takes a lot of tweaking and can get kind of more anal than some want but it can be done. 45 2.1 claims I can't do it. He is wrong. Your the guy that always wants targets and proof. Why don't you follow your own protocals.

I'm not the one having a fit here. Speaking of not tactfull; telling me where to go and what do is definately not being tactfull. You make a denegrating statement of my abilities and then chastise me, get serious. You can't handle the heat in this discussion stay out of the kitchen. I'm not the one calling people stupid in posts. Should you stop calling people names and whining about them not reading your posts and lockstepping with your opinion, maybe you wouldn't have to be chastised and you might regain some credibility. Finish your tests and present the data. Most people here can decide for themselves whether they believe you or not without your brow beating them into submission.

Bass Ackward

05-07-2008, 06:51 AM

Well, let's see what Larry's distance testing of the failed HV loads shows.

That will answer a lot of questions and maybe generate others.

I was curious and I shot a load I new was trashy because of temperature yesterday. I just used 100 and 200 because I don't have a safe setup to do 50 yards for rifles. 100 was 5 3/8" and 200 was actually 9 7/8ths. (Rifle was clean and the second 5 shot groups always does better) I used a 36X scope, so I couldn't blame sight for any error.

This appears fairly linear to me. So the reason for inaccuracy for this load wasn't from RPMs in my opinion. That is 180,000 RPMs.

As temperature warms up, this load will get better. :grin:

Tiger

05-07-2008, 11:55 AM

runfiverun

05-07-2008, 11:58 AM

bass that is fairly linear, your 200 group is also near the same size as mine.
but your 100 yd group is near double mine..
what is really going on here ? i know you have shot that boolit before..

it is nice to see some groups posted that are not 1/4" at 1000 yds for once though.

leftiye

05-07-2008, 12:23 PM

Bass,
Velocity? With 180,000 rpm, It probly wasn't poking along, I'd guess.

R5R, A little better than linear. But groups don't settle down (Larry?)? Like I said before, it happens all of the time. One group doesn't prove anything. But a million groups, Two at a time does, maybe?

Larry Gibson

05-07-2008, 01:35 PM

Bass

I'll just answer your post. Was this with your 154 LBT? How many shots in the groups? What velocity? Assuming a 10" twist that would be around 2550 fps?

Yes that was fairly linear. Let's do wait until I complete the HV test.

Larry Gibson

Larry Gibson

05-07-2008, 01:40 PM

45 2.1, leftiye and Ralf

Say what you will. I will not answer any more of your posts. You continuously rehash the same old stuff over and over, I tire of answering. I also tire of the personal attacks. If some of your questions and/or statements are stupid and I call it then so be it. Don't try to BS everyone here and say you have the moral high ground. You are not on the moral high ground, you all have made similar comments either directly or with inuendo. However it doesn't matter as I'll not engage in any further conversations with any of you. I am not embarased any in the least for the deleted post. I hit the wrong key and it entered the post before I was finished. I think everyone can see that the deletion was the beginning of the next post. I don't believe the content of that post was one of emabarassment.

I must admit to some embarrassment though; that is trying to present facts and intelligent discussion with the three of you. I have been told by many to just forget answering you three as all you want is arguement and you will not listen to reason, right of wrong. They were right, I am embarrased and apologize to them for the extended nonsense here. No more from me as I will stick to conducting the tests regardless of what you post.

Good day gentlemen.

Larry Gibson

sundog

05-07-2008, 02:30 PM

I've been mullin' somethin' fer a spell.

When you shoot for trophies, braggin' rights, and sometimes money, you shoot your MOST accurate load. It doesn't make any difference the velocity.

I usually take a few minutes with every issue of 'The Fouling Shot' when it arrives and scan the match results. Most of the calibers represented are 30 BR, .308, 30-06, 32 Miller Short, 30-40, 32-40, and a few others. It appears all of the rifles in use are either bolt or single shot. I assume they are all over the place from box stock to all custom. Powders in use for other than the smaller cases are in the 4227 to Varget range. Just about everyone is shooting GC boolits, and just about everyone is in the 1600-2200 fps range. Boolit weights seem to run in the 180 - 210 range. These guys and gals shoot some very respectable scores.

So..., what I'm pondering is if HV can be ACCURATE, how's come all these folks are 'stuck' in the rut? After all, this is about accuracy. Isn't it?

Here's the other thing I'm thinking. Even if you can get an accurate HV load, is it consistently repeatable? If the answer is no, then it's not worth anything. Loads that are not CONSISTENTLY accurate, are not accurate.

45 2.1

05-07-2008, 02:49 PM

I've been mullin' somethin' fer a spell. When you shoot for trophies, braggin' rights, and sometimes money, you shoot your MOST accurate load. If your allowed to, which in some cases your not allowed to compete with certain guns and loads. It doesn't make any difference the velocity.Within the confines of the match rules and conditions you've entered.

I usually take a few minutes with every issue of 'The Fouling Shot' when it arrives and scan the match results. Most of the calibers represented are 30 BR, .308, 30-06, 32 Miller Short, 30-40, 32-40, and a few others. It appears all of the rifles in use are either bolt or single shot. I assume they are all over the place from box stock to all custom. Powders in use for other than the smaller cases are in the 4227 to Varget range. Just about everyone is shooting GC boolits Not the 32-40 boys. They breech seat as well as some of the 32 Miller guys., and just about everyone is in the 1600-2200 fps range. Boolit weights seem to run in the 180 - 210 range. These guys and gals shoot some very respectable scores.

So..., what I'm pondering is if HV can be ACCURATE, It can as many people have proved and written about. how's come all these folks are 'stuck' in the rut? After all, this is about accuracy. Isn't it? The assumption, it would seem, is that its only for group shooting. It isn't. Some people hunt big game with high velocity lead, shoot silohette matches, shoot groups etc. Everything involved with high velocity usually dictates distance and a accuracy requirement along with wind doping. Or the satisfaction of just doing it for fun.

Here's the other thing I'm thinking. Even if you can get an accurate HV load, is it consistently repeatable? If the answer is no, then it's not worth anything. Loads that are not CONSISTENTLY accurate, are not accurate. You shoot matches, are your loads consistently accurate? To what degree? Or does it depend on the ambient conditions and just how well you do. The old timers used a mechanical rifle rest to take out the human element. How many here have even tried that to determine accuracy of the rifle and load itself.

45 2.1

05-07-2008, 02:52 PM

Say what you will. I will not answer any more of your posts.
Larry Gibson

It seems you leave when the questions get to difficult or you don't want to answer them. More wiggle wiggle wiggle.

Larry Gibson

05-07-2008, 03:18 PM

Sundog

Your post is relevent, pertinant and correct. Some do not understand the difference between "best accuracy" and "hunting accuracy". Many try to have both at the same time and that is possible with jacketed bullets. However when you talk about regular cast bullet hunting loads pushed to HV in faster twist rifles then some trade off is necessary. Some also continuously use results that are not even used in the RPM threshold or above it.

Larry Gibson

sundog

05-07-2008, 03:20 PM

45, I don't know what kind of a burr you got under your saddle pard, but your comments, as far as I am concerned, are out of line. I made some general observations about something, posed at idea or two, and you act like I committed a capital offense.

Are you actually going to tell me that you will not shoot your most accurate load in a match? Really?

It seems like you have to be RIGHTer than anyone else. So, tell you what, you take it and do what you want with it. I'm done.

leftiye

05-07-2008, 03:21 PM

Dern! Larry accuses us of everything that's been driving me nuts about his non-answers. When I was a young man I came to believe (was gonna say learned) that this is one of the most salient features of an abnormal interpersonal situation - when both parties were saying the same things about each other.

Larry, if you dealt with issues, no one would have cause to continue bringing the same issues up again and again. It's not us quoting your ideas, and your study over and over either. But, it does save you from losing the argument - doesn't it?

Larry Gibson

05-07-2008, 03:34 PM

I haven't lost the arguement (assuming the concept of the RPM threshold). I have already admitted I will if proven wrong by actual testing. I wonder if others are as willing? Seems though it is just the usual "since you won't agree with me" I'll just keep saying you are giving non-answers and avoiding issues. Some should actually read what I've said. They don't have to agree but at least they should read it. I see no reason to agree with their postulations until they provide facts that prove those postulations. Might be nise if their postulations were pertinant to the question also.

Larry Gibson

leftiye

05-07-2008, 03:37 PM

Sundog, Regardless of who is doing it at the moment, that is a big part of what has been wrong with what has been posted here. Both the demonizing of dissent, and those in reciept of the abuse becoming sensitized to it and percieving more abuse than was intended. 45 2.1 didn't agree with you somewhat it seemed to me. Not taking his part (he's p!$$t me off a time or two too), maybe just don't take it too personal. Heck, at least he answered you! Point by point even. Right -ER?, don't we all?

runfiverun

05-07-2008, 03:42 PM

come-on
you guys keep saying that everything else matters but not twist rate[rpm's]
if it matters , it all matters!!!
with even a jacketed bullet all i hear is how they are more accurate when you donot
shoot a maximum load.
the only exceptions that i can think of are the short mags..
high velocity is obtainable with cast boolits.........the question is accuracy...
in my case i am trying to see what it takes at different yardages...
everything that is put in a thread is there to be read and discussed.
if you have a better or different way to do something say so..
this has to be the longest thread i have ever seen on any forum and only [maybe half]
has to do with the sublect.

leftiye

05-07-2008, 03:46 PM

Larry, Sounds like more of the same to me.

Larry Gibson

05-07-2008, 03:59 PM

Tiger

05-07-2008, 04:26 PM

Sundog

Maybe way off but all the time shooting of high velocity loads not so much fun. I think this explains why 22 rim fire so popular besides the most noticeable things lack of recoil low noise and cheap.

Ralf

Tiger

05-07-2008, 04:30 PM

runfiverun

05-07-2008, 04:35 PM

attacking an observation and a valid point is out of line..
you guys are attacking larry with things he hasnot even tested yet.
and he is telling you where his tests are pointing, then y'all tell him he is wrong.
before he can even get to that point of his test.
if [when] he gets to the point of failure [accuracy change] be it 20" or whatever
i am sure he will say so, if it dont happen, i am sure he will say that also.

amazing what you can observe from typewritten letters about a persons character.
there are quite a few people on this forum i would go fishin with,and a few i would
take fishin.

Larry Gibson

05-07-2008, 05:36 PM

I want to say something about testing. I would feel more comfortable if more professional testing done like military ballistic lab. Not to say you are lousy shooter Larry no no not at all. You know labs they do everything some kind of crazy way. They try to eliminate all errors. Then we get results from creditable place.

Ralf

If all of our knowledge about cast bullets were just based on "lab" testing we would be pretty ignorant. I guess that could be said about a lot of knowledge gained by mankind.

Also if you read Dr. Oehler you will note it is not about where the tests are conducted, but how the tests are conducted. I have layed out my testing criteria and have described and measured the conditions. I seriously doubt whether a multi-million dollar "lab" would change how bullets are effected in flight. I am using shooting techniques and loading techniques that have been "standard" for many years when conducting tests such as this. Additionally I have the equipment to measure pressure, velocity and time of flight among other things. If you can point out a specific way an improvement of a "lab" may provide better information then please advise.

Larry Gibson.

Larry Gibson

45 2.1

05-07-2008, 05:53 PM

45, I don't know what kind of a burr you got under your saddle pard, but your comments, as far as I am concerned, are out of line. I made some general observations about something, posed at idea or two, and you act like I committed a capital offense. I was trying to point out that other shooting games have different rules.

Are you actually going to tell me that you will not shoot your most accurate load in a match? Really? Correct, by match rules. The BPCR games for instance do not allow smokeless or duplex loadings in most matches. My most accurate loads for a buffalo rifle use smokeless which isn't allowed. Next most accurate is duplex loads, again not allowed. That leaves BP, which the BP guys says is more accurate than smokeless, just ask them, but they won't go there at all against a smokeless load. Ask Buckshot whether he can shoot certain rifles in his matches. He has said they do not allow him to shoot his most accurate rifle in some of the matches. Other games issue you ammo instead of what you brought to shoot. Your military rifle matches don't allow jacketed, do they? Is your cast load more accurate than your jacketed loads?

It seems like you have to be RIGHTer than anyone else. That was not my intent. About everyplace in this country operates under somewhat different rules when attending matches, made up by individuals who have their own ideas of what to do. Same here, same where your at. We used to have a combat match league where I live, twenty some odd years ago and you never quite knew what was going to be allowed or done at one. I answered your post because you asked it in terms of a question or supposition. Not to inflame you or anyone else.So, tell you what, you take it and do what you want with it. I'm done

leftiye

05-07-2008, 06:30 PM

leftiye

05-07-2008, 06:40 PM

"attacking an observation and a valid point is out of line.." Run5run

First, it ain't valid. That's what all this is about. And attaking a position is like choosing a religion. One is free to choose whatever they choose to agree or disagree with. They aren't however a law unto themselves when it comes to deciding what is relevant.

leftiye

05-07-2008, 06:50 PM

runfiverun

05-07-2008, 07:24 PM

providing an opposing observation, or fact is the better way to state
an opinion.
and i believe sundogs observation was a very good way to state his opinion.
he was stating where his info came from and what it was.
i have seen others do this during this CONVERSATION.
all that has been asked is what are your observations and what are they based on?
simple enough.

onceabull

05-07-2008, 08:58 PM

45 2.1: Get to Quigley,shoot all the smokeless you want, show everyone up...One thing to remember though, the results get posted on the internet...:!: Onceabull :!:

waksupi

05-07-2008, 08:58 PM

Larry Gibson

05-08-2008, 02:25 AM

"If all of our knowledge about cast bullets were just based on "lab" testing we would be pretty ignorant. I guess that could be said about a lot of knowledge gained by mankind." Larry Gibson

Larry, my point exactly as concerns your recurring taunt that we don't bother you unless we are members of the "I have a test club". Whazza diff?

Conducting a test where parameters are narrowed down to isolate the specific issue and accurate measurements are taken in a scientific manner. Sterile type laboratory conditions are not necessary as long as the conduct of the test is consistant. This gives measured results of what did occur instead of postulations on what might or might not occur. That's the "diff".

Larry Gibson

Larry Gibson

05-08-2008, 02:30 AM

Leftiye

If you don't like what I post why don't you just show us some tests of your own. All you do is just ask questions not related to the test results I posted. If you really want to be a dog in this hunt lets see some of your work.

45 21.1s comments to sundog were out of line.

Larry Gibson

Larry, that too just sounds like more of the same. Answer the question for a change. If everything that challenges your favored line is irrelevant, then discussing anything with you is a waste of time. Mouthwash!

My post was in response to; "Larry, Sounds like more of the same to me." which was your last post before the one you quote. There is no question in your post, it is a statement. I answered with a statement. If you are going to interject kindly keep track of the conversation, it avoids confusion.

Larry Gibson

45 2.1

05-08-2008, 07:11 AM

45 2.1: Get to Quigley,shoot all the smokeless you want, show everyone up...One thing to remember though, the results get posted on the internet...:!: Onceabull :!:

Only if I get to meet and shoot with you. You will be attending.?

leftiye

05-08-2008, 12:54 PM

Leftiye

If you don't like what I post why don't you just show us some tests of your own. All you do is just ask questions not related to the test results I posted. If you really want to be a dog in this hunt lets see some of your work.

45 21.1s comments to sundog were out of line.

Larry Gibson

Larry, that too just sounds like more of the same. Answer the question for a change. If everything that challenges your favored line is irrelevant, then discussing anything with you is a waste of time. Mouthwash! Leftiye

My post was in response to; "Larry, Sounds like more of the same to me." which was your last post before the one you quote. There is no question in your post, it is a statement. I answered with a statement. If you are going to interject kindly keep track of the conversation, it avoids confusion.

Larry Gibson

Larry, Just more of the same! Who cares?

leftiye

05-08-2008, 01:07 PM

Quote:
Originally Posted by leftiye
"If all of our knowledge about cast bullets were just based on "lab" testing we would be pretty ignorant. I guess that could be said about a lot of knowledge gained by mankind." Larry Gibson

Larry, my point exactly as concerns your recurring taunt that we don't bother you unless we are members of the "I have a test club". Whazza diff? Leftiye

Conducting a test where parameters are narrowed down to isolate the specific issue and accurate measurements are taken in a scientific manner. Sterile type laboratory conditions are not necessary as long as the conduct of the test is consistant. This gives measured results of what did occur instead of postulations on what might or might not occur. That's the "diff".

Larry Gibson

You're right larry, but as usual, that wasn't the issue. My point was that the logic you use to negate laboratory conditions is the same as mine when saying that I don't need to have (not necessary) a test to ask a question that challenges your position. If a question is asked, it deserves an answer, not some crap about "I've got a test, do you? Followed of course by not addressing the theoretical question. My problem isn't with tests, nor facts: It's with your argumentation style (you offer oatmeal instead of answers). All of this is a waste of time, Larry.

Larry Gibson

05-08-2008, 01:46 PM

Leftiye

Yes it is a waste of time. Do you know the "diff" between ignorance and stupid?

You do not ask questions, you make statements. I answer questions that are asked. If you do not like the answer that does not mean I did not answer. Those who criticise what I am saying, doing and testing should come up with some sort of facts to back up their criticism. That is how it is done, not by whining about non-answers because they don't agree with you. It is not for me to answer every little whim someone thinks of. If they do not think the results of the test are correct or my interpretaion is correct then it is up to them to prove otherwise. Because you or they don't think so does not make it right, it needs to be proved by you or them.

I am attempting to enlighten your ignorance. However if want to continue to be like a bugger on my finger I can't wipe off that's ok also. If you want a straight answer then ask a straight and direct question. However when you tell me "don't tell me this either" or some such nonsense then it is obvious all you want is agreement. If you don't like my answers that's ok but quit whining that I don't answer when in fact I do and everyone sees it. It's only making you look other than ignorant. Ask the question; I will answer the question. That should be simple enough to understand.

Larry Gibson

leftiye

05-08-2008, 05:14 PM

More oatmeal. Don't denigrate, and insult me about this Larry - get on with developing a style involving answering questions directed at you, and one which doesn't involve fallacies, and Prove it with your actions.

Larry Gibson

05-09-2008, 07:53 AM

Leftiye

Why don't you take your football and go home. You need to let it be. You piss and moan saying I don't answer the question. I tell you to ask a question and I'll answer it; you only come back with your usual crap.

BTW; just who the hell do you think you are to tell anyone to; "get on with developing a style involving answering questions directed at you".

I think, at least, you have proven yourself not to be ignorant.

Larry Gibson

Bass Ackward

05-12-2008, 06:59 AM

So..., what I'm pondering is if HV can be ACCURATE, how's come all these folks are 'stuck' in the rut? After all, this is about accuracy. Isn't it?

Loads that are not CONSISTENTLY accurate, are not accurate.

Corky,

Many reasons.

1. Most benchrest rifles are retired when the throats are worn which is about 1000 rounds. Does the owner want to spend half the guns life developing a load? Or developing a load that may increase throat erosion that may decrease the count to say 700 rounds? (See 4, below)

2. Look at the case capacities these guys are using. If lino is good to 42,000 psi, then the teeny, tiny case capacity (less heat and throat errosion) is going to make this fail at a much lower velocity than with say an 06 at 42,000.

3. How long are the barrels that are used in competition? My most consistent HV load would be 2280 fps out of a 20" barrel.

4. While HV is accurate, it isn't accurate at the way you must play the game to compete. Comps are shot in a timed fashion with warming shots permitted. This creates heat and puts a tremendous strain on lube that lowers overall performance capability. (actually increases throat erosion too) And if you have no guarantee of what the temperature range may be the day of the comp, then you can be screwed again. So a slower load that is less fussy would be the only option for this game.

Your second point is correct. Same for a gun. But the need for accuracy is still defined by the game. Groundhogs at 400 yards that require one or two shots every half hour set a more generous cooling time for that game.

Larry Gibson

05-12-2008, 10:29 PM

Bass

I ran the test you suggested today. I was only able to shoot one 10 shot group at each range. As you know this can give some results that may not be linear. Better would be shooting 3 or 5 groups at each range and working off an “average” group size simply be cause at one range you may shoot the smallest group and at another range you may shoot the largest group. However the use of 10 shot groups does tend to give closer results than 5 shot groups.

I used the 10” twist rifle which is a sporter with a 10X scope on it. The bullets were 311291s cast of linotype. They weighed 171 grains fully dressed. They were sized .309 and lubed with Javelina. Cases were fire formed/prepped cases used with that rifle before. They were NS’d with a Redding Bushing die. Primers were WLRs and powder was H4895. All loads were thrown. A Dacron filler was used in each load. Two loads were tested; 28 gr H4895 at 136,000 RPM and 38 gr H4895 at 179,000 RPM. The test was conducted at Tacoma Rifle and Revolver Club. The benches there are very solid concrete. Targets were fired with each load at 50, 100 and 200 yards. One ten shot group of each load was fired at each range then the barrel was cleaned. Two sighter/fouler shots were then fired before the next two 10 shot groups were fired at the next range.

I did get caught with 2 flinches during the testing. A guy showed up with a .300 RUM with a muzzle brake and set up 2 benches down from me. I’ll point out the flinched shots. He caught me on the 50 yard string of the 28 gr load (3rd shot low to the right) and on the 6th shot (out to the right) of the 200 yard 28 gr load. I also called the high 12 o’clock shot on the 100 yard test of the 28 gr load.

The first picture shows all three of the 28 gr load tests. Note the 4 sighter shots. Nine of the 10 shots (minus the called shot) went into .7” at 50 yards. The nine good shots of the 100 yard test went into 1.3”. At 200 yards the 9 good shots went into 2.5 “. As a side note after all the testing was complete I had 5 sighters left. They were the 28 gr load. I fired them at 200 yards and they went into 2.75” so I think that is a pretty god indicator the load is capable of 2.5-3” groups at 200 yards.

The 28 gr load at 136,000 RPM produced linear size groups at 50, 100 and 200 yards (.7, 1.3 and 2.5”).

The second picture is of the 50 and 100 yard 38 gr load groups. At 50 yards the group was 2.55”. At 100 yards the group was 4.7”. Now that gives us an indication that the 38 gr load is also producing linear groups. However, when we see the 200 yard target (3rd picture) we see the devil has popped up. That group is a 14.5” one and is not linear progressively to the 50 and 100 yard groups. To be linear the 200 yard group should have been around 8 - 10 “.

In case you didn't notice the 38 gr load at 200 yards was 10.25" larger (12" larger not counting the called shot) than the 28 gr load. Also note the 28 gr load was as accurate at 200 yards as the 38 gr load was at 50 yards. All in all the 38 gr loads groups at 179,000 RPM do not look all that linear to me.

Larry Gibson

Bass Ackward

05-13-2008, 06:56 AM

Larry,

I knew by the detail of the first two paragraphs what the outcome was going to be. :grin: Concrete benches? Like that made a difference? Did you eat baked beans before this string too? :grin:

All you gotta say was they weren't linear. And or post the targets since you had'em.

Appears that in your case you have RPM syndrome. Good thing you tested for it. :grin:

I tried the same load that was linear to 200 on out to 400 yards. (the other hill side) Somewhere between 200 and 400, the load went totally non linear and you could hear weird sounds. Couldn't hold 10 feet. So it appears I have RPM syndrome too. Just at a different range. I am just traveling faster with a better BC to begin with, so I get to go farther before I crap? (Don't let me lose you here) Apparently forward velocity was holding me stable (straight) until I lost enough velocity that a course change was made and the slug went totally unstable.

Now is the course change made out there because RPMS is still spinning about the same and forward momentum is lost enough that RPMs and air then diverts it? I would say here is your RPM effect.

This would explain low velocity and RPM wadcutter failure at 50 yards in addition to HV problems too. It would also explain why slower twist rates give you better accuracy and more distance before wild groups occurred if the slower twist rate was still adequate to produce stable flight. Meaning that 14 twist was the most accurate of your guns even though 14 twist will not stabilize over a 168 grain slug. At some distance farther out, that would flutter and go nonlinear too. Just less RPMs to cause it so velocity held it somewhat linear or straight even if it wasn't MOA.

How much does your 311291 weigh all dressed up anyway?

So ..... (new question) do " ALL " (cast and jacketed) loads go wacko at some magical distance with the key being to get one that doesn't as far out as you want to shoot?

This load heals itself above 80 degrees and does something correctly enough that it does well out to 400 yards. If I hardened it it would be kinda OK now. So if you believed solely in RPMs levels as the cause for inaccuracy directly from the muzzle, that would be incorrect. This load would never be possible. So there is still more going on here than can be defined (or pinpointed) by a single cause. But I would say that the RPM effect happens at any RPM level once velocity is no longer sufficient to provide forward flight.

felix

05-13-2008, 08:32 AM

John, what you have just said is what long-lived pitchers (the gun and load) learn early in their career. Those that make it through their 30's (years) not only know what day (ambient conditions) they can perform, but also the capabilities of the hitters in the opposing lineup (the target size). ... felix

runfiverun

05-13-2008, 10:07 AM

larry, i should have just mailed you my targets to post.
but you were able to make copies on your own...
bass that part about when it all falls apart is almost the exact same thing i noticed
and posted on one of the other test results pages.

question is now that we know what it does how do we use this?
i mean if i want to shoot 600 yds do i just crank up the vel to 2500 fps and let it
fall into the target?

Larry Gibson

05-13-2008, 11:24 AM

Bass

I knew by the detail of the first two paragraphs what the outcome was going to be. :grin: Concrete benches? Like that made a difference? Did you eat baked beans before this string too? :grin:

I'm not exactly sure what you're trying to say here; I stated the conditions of the test and what occurred. I think you knew what the outcome would be regardless of what I've said, you've seen it too many times yourself. As to the concrete benches, yes they do make a difference. Unless of course someone wants to hypothesize as to the how cast bullets shoot better at HV off the hood of the PU or a card table. I didn't eat baked beans but the concussion from that .300 RUM was nasty enough.

All you gotta say was they weren't linear. And or post the targets since you had'em.

Are you saying I faked this test with targets I had laying around? I "had'em" because I shot them yesterday just as described. If you'd bother to look at the targets and what I wrote you'ld see that only the 38 gr HV load was not linear. The 28 gr load was very much linear. The 38 gr load was not. That was all I gotta say? That was the question wasn't it? You are the one who requested this test saying it would determine if it was RPM or not, aren't you?

Appears that in your case you have RPM syndrome. Good thing you tested for it. :grin:

The problem is, even you have "RPM Syndrome".

I tried the same load that was linear to 200 on out to 400 yards. (the other hill side) Somewhere between 200 and 400, the load went totally non linear and you could hear weird sounds. Couldn't hold 10 feet. So it appears I have RPM syndrome too. Just at a different range. I am just traveling faster with a better BC to begin with, so I get to go farther before I crap? (Don't let me lose you here) Apparently forward velocity was holding me stable (straight) until I lost enough velocity that a course change was made and the slug went totally unstable.

You're not going to "lose" me here.

Now is the course change made out there because RPMS is still spinning about the same and forward momentum is lost enough that RPMs and air then diverts it? I would say here is your RPM effect.

We all know the longer the range the greater the effect. Wasn't that your point in asking me to conduct this test? You see you already knew the answer to the question. It is RPM as you've just shown. You got the same effect only at a slightly longer range because you are using the better designed bullet for HV.

BTW; It's not just my RPM effect. It's yours too, along with everyone else.

This would explain low velocity and RPM wadcutter failure at 50 yards in addition to HV problems too. It would also explain why slower twist rates give you better accuracy and more distance before wild groups occurred if the slower twist rate was still adequate to produce stable flight.

Not so. Take standard WCs out of a S&W 6" revolver and they will crap out between 50 and 100 yards. Take the same WCs out of a Colt 6" revolver and they will be accurate past 100 yards. The reason is the S&W has a 18 3/8ths twist and the Colt has a 16" twist. It's the faster twist of the Colt barrel that keeps the WCs stable and more accurate to a longer range.

Meaning that 14 twist was the most accurate of your guns even though 14 twist will not stabilize over a 168 grain slug. At some distance farther out, that would flutter and go nonlinear too. Just less RPMs to cause it so velocity held it somewhat linear or straight even if it wasn't MOA.

All bullets need a certain level of velocity to maintain accuracy and rotational stability over the course of it's maximum distance. How much velocity is dependant on the twist. If the twist is not fast enough the bullet loses rotational stability at reduced velocity.

Actually the 311291s used in the Chapter 2 test weighed 177 grs so if "that 14 twist was the most accurate of your guns even though 14 twist will not stabilize over a 168 grain slug" how do you account for the 14" twist being the most accurate? Since you are guessing "At some distance farther out, that would flutter and go nonlinear too" I shall make a guess that it won't do that out to where it begins to go subsonic. Or perhaps that's not a guess on my part(?).

How much does your 311291 weigh all dressed up anyway?

Bass, if you'd really read my post you'd see what it weighs as the answer is there. Instead of skimming through the post please read it before making assumptions.

So ..... (new question) do " ALL " (cast and jacketed) loads go wacko at some magical distance with the key being to get one that doesn't as far out as you want to shoot?

Would be nice if you'd answer this question in plain English first?

However the answer to your "next" question is "no". "All" bullets do not go wacko at some distance. It depends on the rotational stability and whether the BC of the bullet allows it to maintain sufficient velocity during the course of it's flight if fired at max elevation for maximum range.

That 28 gr load and it's equivalent load in a 10" twist 06 have been shot to 500 yards with complete success. Beyond that the bullet is dropping subsonic which is another story. However out to that time the groups open up in a very linear fashion.

This load heals itself above 80 degrees and does something correctly enough that it does well out to 400 yards. If I hardened it it would be kinda OK now. So if you believed solely in RPMs levels as the cause for inaccuracy directly from the muzzle, that would be incorrect. This load would never be possible. So there is still more going on here than can be defined (or pinpointed) by a single cause. But I would say that the RPM effect happens at any RPM level once velocity is no longer sufficient to provide forward flight.

[B]"“Larry should use the same top end loads that he did in this test that the slow twist performed better than the fast. Keep this simple. We know that the slower twist is going to shoot these more accurately, he already proved that. Right now we are drawing the conclusion that it is RPMS that is the reason.

If groups are radically bigger with the faster twist rate at 200 than they were at 100, then Larry has proven the RPM theory. If the groups from all twist rates are all linear, then RPMs was NOT the reason for the inaccuracy.

Let's identify the enemy that needs fought.

Added: Really Larry only has to do this with the 10 twist at first. It should be the WORST of the three twist rates. If it is wild, then he has satisfied me and he can continue with the other twists if he wants. If the 10 twist is poor, but still linear, then why waste his time and components? Cause RPMs won't be the problem.”

So are you now reneging on this?

You said; “If groups are radically bigger with the faster twist rate at 200 than they were at 100, then Larry has proven the RPM theory. If the groups from all twist rates are all linear, then RPMs was NOT the reason for the inaccuracy.”

The test does reveal that thr HV load groups are much bigger and non-linear at 200 yards than they were at 100 yards. According to you that then "has proven the RPM theory".

So now that the test reveals an answer you obviously don’t like you come up with other “questions”?

You ask for this test, you set the conditions to this test and you said what it would prove and I agreed to those conditions, what it would prove and would conduct the test. Now that you don’t like it you renege.

I expected better of you Bass.

Larry Gibson