RPM Testing the 311291

[Bass Ackward]

People are too worried about the election, so I decided to get your mind off of it for awhile. I finished shooting the 311291 belonging to Larry Gibson after educating myself in many way as to why. Here are some of my findings.

The nose portion of this bullet did not fit any of my 06s at .298 using my mix, so I stayed with my 700 Remington with 36X scope for all shooting. The control load for my low velocity to HV testing was 16 grains of 2400 often quoted as the universal load. With this load, the average for three, 5 shot groups was 2 1/8”. So that was my low velocity accuracy standard that had to be beaten. I was supposed to beat it over 140,000 RPM. The poor low velocity accuracy standard was what it was and not investigated just accepted for what it was.

During summer testing, I was was not able to match or beat it. Every load I tried was way over the pressure / velocity that Quickload predicted and it clearly looked like I had an RPM effect. Lube change didn’t matter, hardness didn’t matter. First three shots might be less than MOA, but the last two would put me either slightly above or way above the accuracy standard. Only one powder showed even this promise do the job which was Accurate 3100. Then I could hold 3, 5 shot groups at 2” using 49 grains if I let the barrel cool. This was 2100 fps or 151,000, but groups got worse the more they were shot.

Cooler weather has made a difference. And actually now 52 grains is now the accuracy point at 2300 fps or 165,000 with the same hardness and lube. Three, 5 shot groups now will average 1 ¾” which is less than the low velocity accuracy standard, but not by much. And I still have to let the barrel cool between shots. Quickload says 30,000 psi is maximum for lead in this weight and design unless it gets cooler or I get taller rifling. This design is clearly not for this rifle. But why so poor?

I took some 180 Speer round nose bullets I had left with the same load. Accuracy was about 2” for the first 5 shot group at 2250 fps. They opened with each group after that to about 2 ½” with the 3rd group averaging 2350 fps as copper altered bore condition and was raising pressure. The jacketed handled the fouling, so it lead me to believe my bedding would have to be altered to get this velocity range tuned in much better than it was. My harmonics was clearly off for this accuracy point.

[Bass Ackward]

So why won’t “this” 311291 work at HV?

I did some measuring. The nose of this design doesn’t fit or make contact, at .298 so that rest of the bullet must hold bore center to work. The bearing length of this design is .600 of a .980 length bullet. That’s only .62% of available weight to contribute to holding bore center and countering rotational forces as they increased with velocity. If the nose tips, the base follows and it is now longer perpendicular with the bore or the crown. So everything needs to be right here. Is it? Why won’t this shoot better?

The group size difference with the temperature change had me investigate. I used a .308 Lee sizer as this is my bore measurement. A single bullet was used. It was molded, weighed, lubed to the hilt without sizing, then sized to bore diameter as a rifle barrel would do minus the rifling displacement that would reduce lube capacity even farther.

Bullet weight:

Naked: 171.1 grains.
GC: 4.3 grains
Lubed w check: 175.8 grains
Sized to .308: 175.6 grains

So this bullet is carrying only .2 grain of lube. No wonder why changing lube or hardness made very little difference. And the rifling engraving would have occupied even more of the lube carrying space, so this design is only going to have minimal amount of lube to work. When that lube is used up, it’s gone. Pressure is going to raise and if you are operating right on the edge already, then you are going over what the slug can handle and accuracy will get worse. The faster you go, the more fouling you leave and the more fouling must be passed. So the more out of balance the bullet gets and out of square square the base becomes. Accuracy will get worse as you go on up. An RPM effect? Clearly, the best operating range for this slug is the point where it first stabilizes and that’s it. Can this design help itself?

[Bass Ackward]

Can it help itself?

I measured the GC groove at this diameter and the gap to remove fouling was only .017. A human hair measures .015. Clearly, the lack of lube was going to leave fouling, but the GC groove was not going to be capable of handling very much before it loaded up. This explained why my groups opened with the number of rounds fired. Meaning that once fouling was left, the next bullet was going to have to iron it on in order to pass it. Just as the jacketed Speers did above. This is going to raise pressure and velocity.

Once the bullet passed, the bullet would be sized down by how ever much it had to to pass this fouling as it built up and no longer contributing to the rotational effort or holding bore center. Same thing as lowering rifling height and unbalancing the bullet at the same time.

So clearly what we have here is a bullet design that as it speeds up can not either prevent or clean up it’s mess. Sort of explains why some of the early bore ride designs had a clean out groove in front of the front band. But lead is only so strong and the best fouling is that which is not left behind in the first place.

Why is the 311291 limited in it’s velocity or accuracy capability?

1. Did not fit well enough that the nose could help it could hold bore center.
2. Not enough bearing area to handle rotational forces as the RPMs increased.
2. Doesn’t carry enough lube to prevent fouling.
4. GC can’t clean up it’s own mess when it does.

So should we draw conclusions from a single design cherry? No, maybe another 311291 cherry might be better. But bullet design can be strengthened considerably so that it doesn’t have to be as hard. Or carry as much lube. Or can be shot faster without fouling. Well, you get the idea. Fit adds strength, but strength of design is better.

Better than the election huh?

[Larry Gibson]

Bass

How cold is "colder weather"? It was 60 degrees here when I ran that bullet through my '06 with 3100 powder. I got no where near that accuracy at that velocity with it. I did however get right at 1" five shot groups with the same 311291 using 4895. I also got 1.75 - 2.25" five shot groups with RL19 and H4831SC at 2300-2400 fps. However, you seem to forget my RPM Threshold test was mostly with ten shot groups. No difference though as we both achieved essentially the same accuracy give 5 shot groups. This was during the continued (after all the hullabalou and I quit posting the results of my continuing RPM tests due to the obnoxious posts of a few) continued and completion of my test. No I will not post the final results test here, just examples now and then as I am now. Perhaps my rifle just doesn't like 3100. Perhaps your rifle just doesn't like 2400. I'd suggest you try working up a low velocity accuracy load instead of just accepting a "universal load" as the best it can do. Makes for a more structured and scientific test that way.

Another couple questions; how much lube does your LBT bullet carry (I already know the answer)? So why doesn't it "run out of lube" with less lube at the same velocity?

However, my point here is to thank you for your tests and conclusions. They once again demonstrate how all the defects of design and all of the things that happen during accelleration (internal ballistics) to a cast bullet. Thus when the cast bullet leaves the barrel the adverse effect of RPM takes over at a certain level with the accuracy deteriorating. This is the RPM threshold. The accuracy may or may not deteriorate a lot. That depends on the things we do in preparing and assembling the load. I do believe we have both stated that numerous times since this RPM threshold discussion began.

One last point; my '06 only has a 9X scope on it, advantage Bass. Just kidding here Bass, I shoot quite well with it even though I'm so "low powered".

Larry Gibson

[45 2.1]

I'd suggest you try working up a low velocity accuracy load instead of just accepting a "universal load" as the best it can do. Makes for a more structured and scientific test that way. Larry Gibson

The same exact thing was suggested to you also and you refused. My my, time and perspective does change things.

[Larry Gibson]

45 2.1

Can't you come up with something new?

The fact is I did work up numerous loads in the RPM threshold test from a low velocity of 1800 fps up through 2800 fps using;

3 different .308W rifles with 3 different twists - 10, 12 and 14"
2 different 30-06 rifles with 10" twists
5 different powders
5 different primers
3 different GCs
6 different lubes
3 different neck tensions
3 different bullets
3 different alloy hardness
6 different bullet sizings
I also measured about everything that can be measured using an Oehler M43 PBL. (if you forgot what all the measurements were refer to my first RPM threshold post and read it)

Just what exactly have you done (like Bass and I) to prove or disprove the RPM threshold besides flap your jaws?

I also accomplished the exact same thing that Bass has. Had you simply waited for the test to be completed and all the results of the test to be posted you would know that. However you chose to argue and second guess everything beforel the test was even completed. If you could even recall (that is if you even really read it) the first post on the RPM threshold test you'd remember I said i was going to also see what could be done with the 311291 in the '06. I did exactly that and achieved the same results as Bass.

Do you have a point other than to simply argue! This is the last I will discuss this issue with you unless you get reasonable and make a contribution backed by a test or can ask a reasonable question.

Larry Gibson

[45 2.1]

Indeed Larry, perspective does change things, now you have turned your results around without finishing your tests or publishing the results.

Larry wrote:I did exactly that and achieved the same results as Bass. Well, it doesn't appear that way. Bass got better groups at higher velocity past your so called RPM threshold and you didn't. All with the same mold, but different methods.


How Obama of you.

[Larry Gibson]

Folks

Apparently 45 2.1 can't read. I believe I distinctly said the RPM threshold test was finished (has been for a couple of months) and why I won't post the results. Inane posts like 45 2.1s is the prime reason. How inane? In one sentance he says I haven't "published the results" and in another sentence says I've "turned the results around". How does he know if I've not published the results? Inane indeed! I also distinctly said I got the same accuracy with 311291 at 23-2400 fps as Bass did except I did it with RL19 and H4831SC. Yet 45 2.1 says, "Well, it doesn't appear that way". Perhaps he can't read well because he needs glasses.

Many of you have PM'd me wanting me to post the results of the RPM test. You now see why I won't. The reason is simply because of the continual inane and rediculous responses it gets from 45 2.1 and a couple others.

I also find his "How Obama of you" to be totally dispicable and insulting to everyone on this forum.

Larry Gibson

[45nut]

I too find that offensive and wish the name calling would cease, now. There is no reason for it when discussing such topics.

[Bass Ackward]

However, my point here is to thank you for your tests and conclusions. They once again demonstrate how all the defects of design and all of the things that happen during acceleration (internal ballistics) to a cast bullet. Thus when the cast bullet leaves the barrel the adverse effect of RPM takes over at a certain level with the accuracy deteriorating. This is the RPM threshold. Larry Gibson


Larry,

Ah ......... sorry. That is not what my data showed. My testing explains yours and mine.

My groups were shot at 50 and 100. The 100 were double the 50 and not worse. That means that RPMS was NOT the cause of what ever accuracy or inaccuracy I got, nor was RPMs affecting me negatively at least to that distance.

You asked WHY you don't get the same results? You do, you just interpret it incorrectly. :grin:

Your slower twist rate damaged bullets less in your bore so your bullets held center better and broke seal squarely. This means that muzzle pressure caused less yaw in your slower twists and thus bullets stabilized sooner to travel straighter or more accurately. That's what your testing showed me. Slower twist has the the same result as a longer barrel. Better launch.

It's all about the launch. That's what I interpret from all of this at least to this point. And fouling and heat are the true enemy. Same with jacketed just amplified with cast cause it's softer and requires lube.

[Larry Gibson]

Bass

I beg to differ with you. Your testing only confirms mine. Call it a “launch” if you must but the fact remains that the adverse affect of RPM is what causes the inaccuracy of cast bullets above a certain level. My tests with the 3 different twists prove that. If you’ll recall I have always said the RPM threshold could be pushed. How far was the question? In the case of the 311291 we both agreed the way to go was with a larger case and slower burning powder so the bullet would be less damaged during acceleration. I stated in my RPM posts that at the end of the test with the 3 barrels in .308W I would also test 311291 in a 10” twist ’06. I did that and achieved good accuracy at 23-2400 fps with RL19 and H4831SC. You now have done the same thing only with 3100. So you see I don’t interpret anything incorrectly. You shoot sub 2” groups at 100 yards and I shoot sub 2” groups at 100 yards. Not too hard to figure out. However, for joe reloader who asks why can’t he shoot a 311291 “at velocity with accuracy” out of his ’06 the answer still remains; he isn’t going to. “At velocity” for a normal ’06 with 170-180 gr jacketed bullets is 2650-2700 fps. You and I have pushed the RPM threshold with 311291 to 23-2400 fps but neither of us have got the same accuracy at 26-27—fps, now have we? The reason is, though we have “pushed” the RPM threshold it will still bite us above where we are at.

Also, again note, my last tests and the ones I referred to in my post to you were shot with two different 30-06s with 10” twist barrels. The twist I used is the same as you were using. There was no difference between your “launch” or mine. But since you brought up the slower twist I might add that with the 14” twist .308W I have been getting fairly consistent ten shot 2” groups with 311466 at 25-2600 fps. On several of those groups the first 5 shots go into 1” or less.

Some still think the RPM threshold is a limit. It is not. I hope you are not still one of those. It can be pushed but only so far and only under the best of conditions. I’ve not been able to run a 10 shot string with accuracy under 2” with my loads without cleaning the barrel. I’ve tried the magic LBT and it doesn’t perform any better in this regard BTW. We accomplish a pretty nice trick with sub 2” groups at that velocity but it might not be too practical. Again to joe reloader who wants to shoot perhaps 40-50 rounds in and hour of two practice session isn’t going to achieve the same results we have. The reason he won’t is RPM.

Larry Gibson

[leftiye]

"However, for joe reloader who asks why can’t he shoot a 311291 “at velocity with accuracy” out of his ’06 the answer still remains; he isn’t going to." L.G.

I agree, he isn't going to. The reason being the faulty design of the boolit as marketed by Lyman and as outlined by Bass. RPMs only acts upon faults that exist in the boolit's situation as it leaves the barrel (you yourself have said this). If the design is correct, and the load is done so that no erratic yawing, imbalance, and etc. exist, then the whole RPM thing changes upward drastically - you've also said this yourself. Blame the causes, not the effects. Yes RPM does have an effect, but its effects are pursuant to defects found elsewhere and all that anyone can do about it lies elsewhere in removing those defects.

[Larry Gibson]

Leftiye

Congradulations, you've got it. BTW; the "effect" is inaccuracy. The "cause" is all that you say that I've said and RPM. As you say; no defects in the bullets then the RPM has nothing to "effect", adversely or otherwise. The problem is it is very hard to keep a cast bullet from deforming during the higher end accelleration required for higher velocities. In the .308W to get a 160+ gr bullet above 2500 fps is going to take 40,000+ psi. In the '06 you can get a 177 gr 311291 above 2500 fps with psi's in the mid to high 30,000 psi range. Small things like that begin to make a difference as Bass and i have mentioned in previous threads. Good to see we agree, on some things anyway

Larry Gibson

[Bass Ackward]

However, for joe reloader who asks why can’t he shoot a 311291 “at velocity with accuracy” out of his ’06 the answer still remains; he isn’t going to. “At velocity” for a normal ’06 with 170-180 gr jacketed bullets is 2650-2700 fps. You and I have pushed the RPM threshold with 311291 to 23-2400 fps but neither of us have got the same accuracy at 26-27—fps, now have we? The reason is, though we have “pushed” the RPM threshold it will still bite us above where we are at.

Larry Gibson


Wow. I thought this would be a good distraction and it has legs of it's own.

Larry,

This statement here is the foundation of our difference in opinion.

A cartridge has a pressure limit set by SAAMI. If take a look at all the jacketed bullet weights in any reloading manual for any caliber, the highest velocity will be obtained with the lightest bullet weight in every caliber. The key word there is pressure limit. It is uniform for all weights, but it still results in a lower velocity for heavier slugs

With cast, you have a different pressure limit. The limit is now set by lead and rate of pressure. It is a sliding scale and NOT a FIXED limit because of inertia. Factors there are bullet design and fit, weight (inertia) lube and bore condition.

As you go up in bullet weight, you create more inertia that will require a slower rate of pressure rise to reach the same velocity. But in the end, no matter what you do, no matter how much you try, the lightest weight cast bullet will always be able to be driven faster than the heaviest weight. Same logic, just a different "pressure" standard. (that we control)

If my success with a 154 grain bullet peaks and is 2500 / 2600 fps in the 30-06, then it is physically impossible to expect a 175 grain slug to approach that at anywhere near that level unless I can harden it or change any of the factors.

I listed the factors above that will permit a higher PRESSURE limit for the same hardness lead. Better fit, stronger design, more lube capacity or better lube and an ability to clean up after itself. Those 4 things are critical to a new reloader to understand .... WHY he is inaccurate. That is if you REALLY want to help him.

That will be lost if we simply tell him RPMs. Not only is it misleading, it's untrue. When the 311291 failed with heat in July and August, pressure ran up enormously. I was running 2600 fps loads and leading severely. That load was 13 1/4" at 100 yards with round holes. But it was 6 1/2" at 50 yards with slightly oblong holes. Here is the KEY: RPMs WAS HELPING me cause it hadn't fully stabilized it yet at that distance. What failed me was the yaw at the launch.

Bottom line, I was running maximum jacketed pressures and had " ZERO " RPM effect on accuracy. (to that distance of course cause velocity was high enough) 100% of inaccuracy was solely attributable to factors relating to pressure even with the slug WAY out of balance. Can't imagine it could possibly get any worse. Wasn't anything to recover at the back stop to verify my speculation. But it was RPMS that actually helped me get flight under control and stabilize.

So telling someone it's RPMs when RPMs doesn't always have something negative to do with it and it's really something else, just doesn't sit right with me. Fight the battle that needs fought. If you got an RPM issue because you bullet is out of balance, you actually need to INCREASE VELOCITY (rpms) to get the out of balance bullet to stabilize and it will remain stable until enough velocity is lost. It's EXACTLY the same with a handgun on the slow end. Then RPMs works negatively on the out of balance slug when your velocity drops back again.

But the REAL cause for inaccuracy was yaw caused by factors that directly come back to pressure resulting in a failed launch that went really bad. But what RPM you need to stabilize is all in the quality of the launch.

[Larry Gibson]

Bass

Please try telling me something I don't already know about pressures with jacketed and cast bullets. There is no difference in our opinion on that. You took several paragraphs to explain the same thing I said to leftiye in two sentences. We agree on what it takes to get accuracy at high velocity (the 4 critical things you reiterated).

Telling joe reloader that RPM is the reason for his inaccuracy is not misleading nor is it untrue. Fact is, it is true. What is misleading is to not tell him the reason. To just tell him to get another mould, change lube or try a slower powder does not help him understand the problem nor to help him get closer to where he wants to go. He wants to go there with 311291, the lube he is using and the powder, etc. If you don't tell him the reason all that won't get him there is because the bullet is damaged (unbalanced due to the initerial effects of setback during acclelleration) and the increased RPM is adversely affecting the accuracy above a certaian velocity then that is a diservice to joe reloader.

All this is a matter of opinion; mine vs yours I guess. Perhaps a matter of perspective on what we should tell joe reloader. Whatever we tell him does not alter the fact that there is an RPM threshold for regular cast bullets. As I've said repeatidly; that threshold is not a limit. It may be pushed by close attention and balance of the 4 critical things you and I have mentioned.

The fact that the RPM threshold can be pushed does not negate it's existance. This is why most eveyone here can and has loaded any regular cast bullet in a rifle cartridge in rifles with 12" or faster twists up to a certain velocity (most often that velocity is well below the reputed "pressure limit" for cast bullets) with very good and often remarkable accuracy. Then when they try to push that same bullet above that velocity level accuracy goes south. The answer and reason is RPM.

Larry Gibson

[carpetman]

Is Joe Reloader any kin to Joe the Plumber?

[Larry Gibson]

Bass

One last note; if you had enough yaw at "launch" to cause the 6 1/2 and 13+ inch groups then the problem was not one of RPM "helping you". It certainly stabilized your bullets. However, you seem to still think that the adverse effect of RPM is all about it making the bullet yaw and wobble to decrease accuracy. That isn't so. The adverse effect of RPM is all about the center of spin not coinciding with the center of form or the center of gravity. This effect, while adverse to accuracy, does not produce yaw or wobble. It means the bullet will begin a slow spiral off from it's intended path of flight. The holes through a target will still be round. The bullets bullets will fly point forward but just won't be spinning concentrically so to speak. The faster you spin the bullet the greater the spiral away from the intended path will be. This is called "inaccuracy". When you understand how that happens it will clear up a lot of misconceptions you still appear to have regarding the bullets flight. Had you shot your 2600 fps load that gave 13+ inch groups at 100 yards at 200 yards you would have see the non-linear effect that the RPM would have had. I ran that test for you, remember?

This has nothing to do with a bullet "going to sleep" so let's not get side tracked on that issue.

Larry Gibson

[Larry Gibson]

Carpetman

I believe Bass wanted to keep politics out of this...and reference to the election....hope everyone voted.

Larry gibson

[carpetman]

Maybe politics are needed here. Research at this high level and magnitude of importance may be worthy of some federal funding.

[Bass Ackward]

The fact that the RPM threshold can be pushed does not negate it's existance. This is why most eveyone here can and has loaded any regular cast bullet in a rifle cartridge in rifles with 12" or faster twists up to a certain velocity (most often that velocity is well below the reputed "pressure limit" for cast bullets) with very good and often remarkable accuracy. Then when they try to push that same bullet above that velocity level accuracy goes south. The answer and reason is RPM.

Larry Gibson


Then you have a problem. The laws of science don't stop because one has a certain quality rifle or passes a certain number. The RPM theory will have to be up and down the line.

When someone throws 16 grains of 2400 in an 06 with any factory mold and they shoot 2" when the guy next to him shoots the exact same thing and gets 1", then there is only one correct answer.

According to the RPM theory, he is shooting a better balanced bullet that allowed him to shoot more accurately than you.

Going to sound kinda stupid isn't it?

Even worse is going to be explaining why as a fella does a ladder and comes up with a load why accuracy goes south and then comes back. RPMs doesn't quite cover that one.

[leftiye]

Larry, I see you are still on the path where boolits rotate around their center of balance with the centerline of balance parallel to the geometric centerline of the boolit. This can happen, I guess, but only momentarily until air resistance upsets the applecart. The parallel situation is not aerodynamically stable. In all situations with RPMs (with revolution speed not exceeding anything necessarily) the major culprit would be air resistance deflecting the boolit according to whatever aerodnamic defect was produced.

Also, the centerline of balance is not always parallel to the geometric centerline, and revolution causes this situation to automatically yaw ("football"), whereupon air resistance takes over and causes a spiral path around the surface of a cone. This is not about centrifugal, or rotational (angular momentum) forces, it is aerodynamic deflection of an unbalanced boolit which is degrading into total instability. This is when the group sizes and the rate of opening of the groups become non-linear.

What seems to more often be the case is that, as has been said by both yourself, and bass the boolit is well enough balanced (geometric centerline coinciding with centerline of balance), but the launch causes yawing which is then corrected by the gyroscopic effects of centrifgal force, and the boolit "goes to sleep." This then produces a reduction in the apparent angular rate of opening (not actual - the target was registering the spiral path of the boolit around the centerline of the spiral which is in fact the line which reflects the true moa of the group) of the group size. RPMS predicts a non linear increase of the group size which probably only happens when the boolits totally lose stability. In other words only boolits deformed in a significant manner during firing or with insufficient rotational momentum (low RPMs) exhibit this characteristic.

[Larry Gibson]

Bass

Obviously you still have no idea of that the RPM threshold is. I'll suggest you go back and reread the many posts I've made where it has been adequately explained. Your poor example of 16 gr of 2400 in and '06 does not cut it because it does not excceed the RPM threshold. Also to compare the accuracy between two different rifles is not valid either. You are only showing a difference in accuracy with one load between two rifles. It is pretty common knowledge that some rifles are more accurate with some loads than other rifles.

However if you took one of those rifle (doesn't matter which) and began to work up a load with the expectation of working up a load to a velocity of 2500 fps and proceeded to work up to that load then you might have a valid comparison. For example lets take the 1" grouping rifle in your comparison. We work up and down with loads from 12 to 29 gr of 2400 under a 311291. We find we get the best accuracy (1") at 1700 fps with 18.5 gr whith the lowest SD/ES. As we in crease the powder charge up through 29 gr we find that the groups progessively get larger as the powder charge increases and as the velcity increases. The 29 gr charge is giving us 2250 fps with 5" groups. We also compute the RPM and find best accuracy at 1700 fps gave us 118,000 RPM. The 2250 fps load was giving us 156,000 rpm. The RPM threshold for that load with that bullet the way we cast it and how it fit our rifle is 118,000 RPM.

Now lets take that same rifle and that same 311291 only this time we have cast it a little harder and are using a slower burning powder. In working up the load we find our best accuracy of 1" at 1900 fps. As we increase the powder charge above that the accuracy once again decreases and we get the same 5" groups but at 2400 fps this time. The RPM for the 1900 fps load is 132,000 RPM and with the 2400 fps load it is 166,000 RPM. This tells us that with that bullet cast and loaded the way we do the RPM threshold is 132,000 RPM.

Now what I'm saying here is that the way joe reloader casts his bullets which are most often bore riders that are commercially available and the way he loads them with most often recommended loads he is going to hit an RPM threshold where accuracy will go south. That RPM threshold is most often between 120,000 and 140,000 RPM. Where in or below his threshold is wil be dependant on the bullet design, alloy strength, the bullet fit and the powder burning rate. You might want to remember that joe reloader wants a load he can go out and enjoy shooting with, perhaps 30-40+ rounds in and hour. Almost all of them are not interested in shooting just 3-5 shots in an hour and cleaning the barrel between groups. Joe reloader is looking for a practicle cast bullet load to shoot. He wants to know why he can't shoot his cast bullet of 177 gr accurately at the same velocity he shoots his 180 gr jacketed bullets in his '06. The reason is RPM. The laws of science back it up.

You and I and some others know how to push the RPM threshold with cast bullets. It is after all only a threshold that can be crossed and not a limit. Can you load up 30-40+ rounds of those and go shoot them in an hour without cleaning the barrel and expect the same accuracy out of the last 5 shots that we get from the first 5 shots? I don't think you can as you tell tales of only shooting 3 shots all day long to get a sub 1" group from your LBT bullet. That's ok, I can't do it either. I'm still working at it though.

Larry Gibson

[Larry Gibson]

Leftiye

[QUOTE=leftiye;422770]Larry, I see you are still on the path where boolits rotate around their center of balance with the centerline of balance parallel to the geometric centerline of the boolit. This can happen, I guess, but only momentarily until air resistance upsets the applecart. The parallel situation is not aerodynamically stable. In all situations with RPMs (with revolution speed not exceeding anything necessarily) the major culprit would be air resistance deflecting the boolit according to whatever aerodnamic defect was produced.

It is known to happen continuously during a bullets flight, not momentarily. For a good explanation look in Hornady's Manual in the section on accuracy. They explain it there and how it adversely effects even the accuracy of jacketed bullets. That's why we shoot groups instead of all bullets going through the same hole. The trick to accuracy is concentricity so that the bullet is balanced and the center of gravity rotates around the center of form. When this happens you get dispersion, i.e. inaccuracy. Air resitance is indeed part of the culprit also. That is why by measuring the BCs I can tell the degree of this imbalance. The lower the BC the less efficient the bullet is going through the air. Good point.

Also, the centerline of balance is not always parallel to the geometric centerline, and revolution causes this situation to automatically yaw ("football"), whereupon air resistance takes over and causes a spiral path around the surface of a cone. This is not about centrifugal, or rotational (angular momentum) forces, it is aerodynamic deflection of an unbalanced boolit which is degrading into total instability. This is when the group sizes and the rate of opening of the groups become non-linear.

That is all nice in theory but it does not pan out when actually tested. That was demonstraed using the 3 different twists. It is about the centrafugal force of increasing RPM overcoming what ever rotational stability there is.


........ RPMS predicts a non linear increase of the group size which probably only happens when the boolits totally lose stability. In other words only boolits deformed in a significant manner during firing or with insufficient rotational momentum (low RPMs) exhibit this characteristic.

Sorry but RPM only predicts a non-linear decrease in accuracy when the RPM is high enough to over come the rotational stability of the bullet. This does not mean the bullet is totally unstable or even that it yaws or wobbles. For example in the linear vs non-linear test I did for Bass the bullet holes of the non-linear group (over the RPM threshold) at 200 yards were sill perfectly round. Even though that group was over 14". The group of the linear (with in the RPM threshold) was 4.5" and the holes were also nice and round. Bullets do not have to be "deformed in a significant manner" for this to happen. Even a small imbalance has an adverse affect on accuracy. However, the more the bullet is deformed during casting, loading and accelleration the greater the imbalance will be and the greater the adverse affect the RPM will have.

Your grasp of bullets going to sleep is the same as mine.

Larry Gibson

[runfiverun]

having been out in the desert in a snow storm all day, this is all starting to "ring"
again except that the start of this seems to be a pretty good explanation of why
joe reloaders rcbs silhouette, or his lyman boolit ain't cutting it.
i will be working with a new boolit design or two this winter/spring.
actual side by side comparisons of them. loads lubes g/c's and sizes.
using last years data as a base-line with the sub 1" load as a starting point.
i ain't gonna get in this one here though.

but i do wanna thank the guy's who have brought enough of what y'all whom
are interested in this topic. h-v with cast. to light, that you should be able to figure out what needs to be done to reach your goal.
get more equipment .a boolit that carrys enough lube. a twist rated bbl that will work for you,with lands tall enough to help you out.
launch the thing straight,and don't beat it to death in the bbl.
keep trying new things till you get there. be picky about your boolits and don't be afraid to try new alloys.
that's just about all i know about it.
and i'll take the accuracy at whatever velocity i can get it, the higher the better.

[leftiye]

Sorry but RPM only predicts a non-linear decrease in accuracy when the RPM is high enough to over come the rotational stability of the bullet.

Larry! RPM IS (reads - IS) rotational stability!

As fer the rest of that, referring to unstated and unreferenced something or another in Hornady doesn't make any difference, there is nothing given to understand, and nothing to look up. Therefore nothing to consider. Concepts, reasons why - (operant factors) please. Is this like your reference to Sierra's testing (in the original RPM test thread) where you alleged that high RPMs were the culprit, and Sierra actually stated that their ballistic coefficients dropping were the result of instability due to LOW rotational speed?

As before, I am having trouble seeing how all of this inaccuracy can occur with boolits that are straight on, not yawing, not tumbling etc. RPMs (wait for it.......) INCREASES stability, it doesn't cause yawing, tumbling, etc. Other factors like gas cutting, deformation, bad launches cause these. They are then acted upon by air resistance. If rpms causes the aforementioned inaccuracy, - how does it do it sans instability, air resistance, deformation, yawing et. al.???? RPMs could do anything imagineable to a boolit that it wanted to - to include turning it inside out, BUT IN THE ABSENCE OF AIR (RESISTANCE) IT WOULD STILL FLY STRAIGHT. That is - continue in the direction it was already going ( as per Newton).

[Larry Gibson]

If you say so Leftiye. That is not all that Sierra had to say and you know you are taking it out of context. If you don't want to read a simple explanation by Hornady then I tire of trying to explain something that you just don't want to consider. After tonight I wonder if it all matters anymore anyway. Shooting cast bullets in the future may be all hypothetical anyway.

Bass

It was nice talking with you again. Perhaps a different topic next time. I am through here.

Larry Gibson

[Bass Ackward]

Larry,

I am looking forward to how these discussions are going to evolve my shooting in the years to come. This is not a lot of difference in what I already believed in the actual index but I do understand RPMS a lot better. Going back to using a bullet that wasn't specifically designed to fit for my gun has reinforced steps that I have taken over the years.

Sorry that your efforts have been lost on me. I do not understand the RPM theory as it has changed and evolved from our initial discussions and it has never been truly defined. It's not even how people define and use it here. If I had to define the RPM theory in earnest to pass a test to save my life, this would be it.

The RPM theory is a numerical zone upon where you can have the most things wrong and the easiest accuracy can be obtained with a certain weight bullet in a certain caliber based upon statistical results of shooters in the past. And that if you therefore attempt to go above that RPM number, your accuracy will suffer in an ever increasing way for a boat load of reasons and you will NEVER be able to achieve accuracy again.

That's all I get from the theory. Cause that is how it has been used on this board. And how you want to use it to aid new shooters explaining why they get what they get. Cutting to the chase, it is an "expectation index" for those that use it to start. It is a "failure index" for those that use it to quit. Putting any top number is what dooms the theory to fail.

[45 2.1]

That's all I get from the theory. Cause that is how it has been used on this board. And how you want to use it to aid new shooters explaining why they get what they get. Cutting to the chase, it is an "expectation index" for those that use it to start. It is a "failure index" for those that use it to quit. Putting any top number is what dooms the theory to fail.

The RPM theory is just as good of an excuse to use as any for a persons failure to educate himself about what he needs to do to get real accuracy. Insanity was defined as doing the same thing many times and expecting a different answer. Much the same happens if you follow Larry's criteria and expect real accuracy. The criteria for accuracy has been outlined several times on this forum by others than Larry. Go back thru the posts by BABore and myself among others, they will give you the factors needed for you to learn how to get accuracy.

[Larry Gibson]

Bass

Unfortuneate that you so misunderstand the RPM theory. Your definition is only your mistaken impression based on your many arguements against something you obvious still do not understand.

The RPM threshold has been defined by me quite a few times. I'll give it to you once again;

The RPM threshold is that range of RPM where almost all cast bullets will lose accuracy if exceeded. For practical purposes when using a gas checked cast bullet with a BHN of 14-18 the RPM threshold is between 125,000 RPM and 140,000 RPM. But let us remember here that a “threshold is not a ‘limit’.

Also as I've explained in this thread that the level of the RPM threshold applies to the varied techniques that we use. Use a soft alloy and a fast burning powder and it is lower. Use a slow burning powder and a hard alloyed bullet and it is higher. The 120-140,000 RPM applies to the average cast bullet reloader who uses the normal loading techniques as espoused in several manuals, books and magazines. That also has been explained by me over and over. You, 45 2.1, BABore and a couple others say but ahah, I've done this and I have done that that proves you wrong. Well, just as I have also said many,many times; I too have done those same things and got pretty darn good accuracy at higher velocity/RPM. But what we do is not what the regular cast bullet reloader does. His requirements such as shooting 30-40 rounds in and hour accurately are different than ours. The fact still remains that for regularly assembled cast bullet loads from regularly available commercial moulds the RPM threshold is valid. The RPM threshold may be pushed up some as you, others and I have done. However, the adverse affects of RPM will also catch up with us just as they did.

As to it being a "failure index" for those that use it to quit". It is not and that is only your own mistaken perception. It is you who always suggests using a slower powder, etc. but mostly to get the LBT mould. I agree with you on that (though I've found 311466 to be just as good) and thus we both actually view the RPM threshold as not "a place to quit" but rather a place to further our knowledge and ability. Some do quit because they just want to shoot their 311291 as accurate as they can with little fuss. That will keep them in or under the RPM threshold. However there are those that want to succeed such as runfiverun. Those we can help push the RPM threshold. Your negative attitude only distracts from us accomplishing that and finding out what really works (more than once) and what doesn't . For example the use of a slower twist to lower the RPM while upping the velocity. You and a couple others continually argue against it. Yet not only have I and numerous others proved it as fact but the Cast Bullet Association bench rest shooters all use slower twists for that exact reason; keeping the RPM down increases accuracy. Most of us understand that. I, for the life of me, can't understand why you don't understand that.

45 2.1's usual commentary is not worth responding to.

Larry Gibson

[joeb33050]

Larry sent me the results of his ?first? series of tests. I interpreted and statistically analyzed the data, and sent that interpretation back to him with some suggestions.
I will be happy to analyze and interpret anyone's data having to do with the RPM theory, I'd like to get enough data to be able to finish the chapter for the book.
If any of you have data, I'll interpret and send back an analysis that you can check with another to make sure I haven't screwed up.
You guys are going down that last road. We need more data to begin to make reasonably true statements.
Fewer words, more numbers!
joe b.

[crabo]

The only topic more explosive than politics and religion, is RPMs.

[Larry Gibson]

Larry sent me the results of his ?first? series of tests. I interpreted and statistically analyzed the data, and sent that interpretation back to him with some suggestions.
joe b.

joe

Not sure I publicly thanked you on this forum for your analysis of the first series of tests I completed. I thank you now as your analysis and suggestions were most helpful.

I did follow your suggestions and they did further clarify several points as you indicated they would. I subsequently completed 3 other series of tests with the three different rifles in .308W having 3 different twist barrels. In those subsequent series of tests I compared different primers, different powders, different lubes, different alloys, different gas checks, different sizings of the bullets and different neck tension on the bullet. These comparisons were made with 311291 and with 311466. The additional tests were comprised of another 800+ shots. Velocities were tested up through 2800 fps with RPM over 194,000.

I also completed a series of tests with two 24" barreled 30-06 rifles with 10" twists. With those two rifles I also completed a series of tests comparing 3 different bullets (311291, 311466 and Bass's LBT), different lubes, different powders and different sizing of the bullets. I've not yet counted the number of shots in that series but it was quite a few.

All of these tests and their attendant data was captured with the M43 Oehler. A few additional "side bar" tests were conducted (Bass's request for linear vs non-linear group sizes for example) that were not captured by the M43. I have the targets of those tests however. From the amount of paperwork (data) I sent you for the first series you understand the shear volume of paper work with data that I have. I have not done a complete analysis yet. From my preliminary analysis it is readily apparent that the RPM threshold does exist. I have found nothing to indicate anything else. I do continually go back through attempting to find anything that might indicate otherwise. Yet every time I re assess the data it only confirms the existence of the RPM threshold.

Obviously you are aware that I have been hounded into a hole here by several on this board. I regret ever having published the first series of tests. I thought it would excite the membership here and we could proceed with new discoveries. I should have waited until I completed the tests. Instead....well you know what happened. Thus the documents are not available nor are the data. I will only continue to post what I know is fact. Facts, because I have the test data with results that demonstrate the RPM threshold is real. I do not post abstract theory. Several here have made their abject stand against this. They do not listen to what I say; they continue to misconstrue what I say. They do not even try to understand even when I tell them we are saying the same thing and agree with them. Bass's definition of the RPM threshold is a prime example. I don't know how many times it has to be explained. My thoughts now are that they simply do not want to understand, they just want to argue.

I do not want to argue. I will entertain further discussion and explanation as I have with Bass. I have learned from him and he has learned from me. We both agree on that and we've learned from each other on a numerous topics. That's what this forum should be about. We don't have to agree but we should keep and open mind, especially when facts from actual tests are given. (45 2.1 - please don't bring up BaBore's example as I already have commented on it). I have a right to my opinions and thought's also, especially given the amount of testing I've done on this subject. I challenge anyone else to show a similar amount of testing. Yet several here do not allow me my opinions. They believe they are resident experts or such and their opinions are the gospel. I thoroughly appreciate my discussions with Bass even though we do disagree on some issues. We actually agree more than he realizes on the RPM threshold (he just needs to get the definition clear). At least it has been civil for the most part. However 45 2.1's continual personal attacks will not get any further discussion from me. It may indeed end my participation with this topic and this entire forum. I am really tired of it. Perhaps that is what he wants anyway.

Joe, thanks again for your help. And thanks for letting me rant on your dime.

Larry Gibson

[TAWILDCATT]

I don't know nutting about rpms. I only know I shoot 311291 out of a 1903 springfield with 13 gr red dot and at 100yrd will group just about touching.
I lube with Lee tumble lube and dont size .311 cast.:coffee:[smilie=1:[smilie=1:

[Larry Gibson]

I don't know nutting about rpms. I only know I shoot 311291 out of a 1903 springfield with 13 gr red dot and at 100yrd will group just about touching.
I lube with Lee tumble lube and dont size .311 cast.:coffee:[smilie=1:[smilie=1:

Well let me explain a little about RPM as it applies to your obviously excellent load (accuracy wise). You're 311291 over 13 gr O Red Dot probably has a velocity around 1550 fps. That gives it an RPM with the 10" twist of the '03 of 105,000. 105,000 RPM is well below the RPM threshold for that bullet using medium to slow burning powders. However, given the pressure of that load and quick accelleration, that may be close to the RPM threshold for that particular combination. I would ask; if you increase the powder charge does accuracy begin to decrease? If so then you are definately at the RPM threshold for that combination.

if the answer to my question is yes the please notice that you are not "limited", nor have you "failed" by understanding that is best accuracy you will attain with that combination. You certainly can move on to slower powders and some other things and attain a higher level of velocity/RPM. What you simply must remember is that those changes will also have a threshold with regards to RPM. When you reach that threshold RPM will again cause accuracy to decrease.

There is one other caveat; If you are striving for a load you can shoot all day while maintaining 2 moa or so accuracy without cleaning the barrel every 5-10 shots then an RPM threshold of 140,000+/- will be about the limit of the threshold. With your '03 this translates into 1900-2000 fps with the 311291. However, if you are striving to just shoot some nice 3-5 shot groups at higher velocity then you can push the RPM threshold of the 311291 up to 2300-2400 fps. Keep in mind you will not shoot such loads "all day long" or for more than a few shots and maintain such accuracy. Such loads are specialty loads fo those who enjoy such essoteric ventures. Such loads with softer alloys in the 2100-200 fps range are also usefull in your 10" twist '06 for hunting but the barrel must be cleaned every 5 shots or less to maintain such accuracy.

Larry Gibson

[45 2.1]

45 2.1's usual commentary is not worth responding to. Larry Gibson

For not being worth responding to, your doing a lot of talking about it........eh! :mrgreen:

[Bass Ackward]

Every single time that someone has tried to sing that song about RPMS, it is simply a .... part of the accuracy picture because RPMs is required for stable flight so that it must be dealt with. If accuracy were simply RPMs, then a light weight barrel would shoot just as well as a heavy barrel. Hot or cold. IF RPMs were the be all, end all of shooting, then an 8.66 twist Mauser would not be the most accurate with a 115 Speer hollowpoint.

Larry is thinking one dimensionally in his rotation balance equation for cast. A bullet not only rotates around from the spin, it always wobbles front to back around a center of pressure. This center of pressure fights center of balance. C of P acts like a center of balance of a stationary object and moves based upon the forward velocity at any one point. How a cast bullet is designed and what weight it is makes all the difference in the world how it handles RPM.

Lets take the same weight slug. A bore ride or semiwadcutter has weight off the nose to throw the center of balance on the back of the slug. This allows this design to stabilize at the lowest RPM and destabilize at the earliest RPM figure on what would be thought of as the higher end. A center of balance mid point of a slug requires more velocity but goes higher. The forward weighted slug will handle the highest RPM, but it destabilizes the soonest. In my day the M-1 Tank round looked like a nail with the head flying forward. This required 5000 fps velocity. They could have sped up the twist rate, but it would have thrown more pressure too. So a balance had to be achieved.

As a slug expands to fit the steel supporting it, it is shortened, the center of balance changes, and based upon how your slug is designed and how you sized it, may have gone from a mid weighted slug to a rear weighted one that begins destabilization at a lower RPM number even if you are spinning. If you seed that slug up even more, it will re-stabilize until velocity is lost. That is why initial pressure or rate of pressure makes so much difference and you get a higher RPM value using 4831 for a rifle slug than you do Bullseye. It's also why a slower twist rate is better because it allows forward motion sooner than a fast twist would. So while muzzle velocity difference and pressure is not discernible, you will disturb C of B less with a slower twist.

What you just got there is my understanding of flight characteristics for cast. Most factory molds are bore ride designs. Most others to include Loverins are weighted rearward for stability that amounts to what most people think of the RPM zone. While a bore ride design can still launch well if everything is right, it has to be more perfect than a stronger design. Weight is the killer as all the effect is on the base.

If you launch something incorrectly or badly 1 time or a million times, all you get is a statistical accumulation of bad data. Most people fail above the zone because most of their work is IN THE ZONE. You have to learn how to make or achieve what is required if you want to go farther up.

So if anyone wants to understand what I believe and the approach I take, you now have my additions to what is thought of as the RPM theory which is incomplete and ever changing at best.

[joeb33050]

My interpretaton of the question is this: Do bullets shoot more accurately with slower twists = lower RPMs; assuming stability of the bullets? Doesn't mean that the other variables don't count; they do.
We have some evidence that slower twists work better = better accuracy than faster twists at higher velocities. Lower RPMs.
First is the 30BR light bullet slow twist for SCORE in modern benchrest. The 30BR site has a lot on this.
Second is the CBA experimenters ahooting fast with slow twists, accurately. See The Fouling Shot, Sept.-Oct. 2008, pg. 195-18.
Third is the results of Larry's experiments.

My interpretation of this set of 3 lumps of evidence is that there is a STRONG suggestion that stable bullets shoot more accurately with slower twist barrels at higher velocities = lower RPM.

Not proved, proving is hard and expensive. RPM is not the sole, and probably not the most important accuracy determinator.

All the other variables, ctg., powder, primer, bullet, alloy, lube, ........ affect accuracy. To some degree.

To make the suggestion STRONGER, we need more data.
But, my interpretation of the data/evidence we do have leads me to the conclusion that I will specify the SLOWEST twist that will stabilize the planned bullet on my next re-barreling of a gun. Because, at up 200 yards, I know of no evidence that a slow twist/stable bullet combination is LESS accurate than faster twists.
If Greenhill says that the minimum twist for stability is 1:17", I know of nothing suggesting that 1:<17" is MORE accurate. For a given bullet.

That's how I seer it, how about some more experimenting and data?
Thanks;

joe b.

[Larry Gibson]

Bass

Speaking of "thinking one dimentionally". You are stuck on bullet stability. How many times have we been through this and yet you still don't understand. The RPM threshold has nothing to do with the bullets intitial sabilization. Imbalanced bullets are easy to stabilize. Every time anyone shoots any bullet it is imbalanced yet stable. This is because it flies point forward. There are degrees of stability and this effects accuracy. Why? Because the centrifugal force of the RPM is why. If there was no centrifugal force from the RPM all bullets, balanced or unbalance to any degree, would all go through the same hole. The RPM threshold is that point where the centrifugal force has an adverse affect on the unbalanced bullets intended path of flight. This is why imbalanced bullets (remember here they all are imbalanced to some degree) that are fired in or below the RPM threshold exhibit linear dispersion as the range increases. Imbalanced bullets fired above the RPM threshold will exhibit non-linear dispersion as the range increases.

I recieved a PM that reminded me that several of you fail to remember we are also talking where the "best" accuracy is, not "useable" accuracy. A please don't come back with your recent test at only 50 and 100 yards and say there was linear dispersion and you were above 140,000 RPM. Two problems there; 50 and 100 yards is many times not a practicle range to test dipersion. Especially when you are only firing 3-5 shot groups which you do. If you'll recall in my test for you I used 10 shot groups and tested at 50, 100 and 200 Yards. Do that and you will find non-linear dispersion with your load. The second problem is I've already told you over and over that the RPM threshold is not a l"limit" and that it may indeed be pushed up. You may have "pushed it up" to 2300 fps with your load. But what happens at 2400 fps? The accuracy goes south in a big way. All you have done is bump the RPM threshold of your load up to 2300 fps and 159,000 RPM. All you do by your consistant arguements is to further confirm what I'm saying about the RPM threshold. If you would listen to what you are say and compare it to what I am saying you would then understand.

Larry Gibson

BTW; last time I checked the M1 Abrams has a smooth bore main gun. The rounds are fin stabilized. No twist at all.

[Larry Gibson]

Joeb33050

Sir, you are correct.

Larry Gibson

[runfiverun]

just a note here: from my running the same boolit through several rifles.
i seem to use a different powder for each rifle however the results are the same, nevermind the lube, having used 5 different commercial lubes plus mixing and using home made lube and mixing commercials and commercial with home made lube.
and only two different g/c's.

same results: this boolit gets its best results [within larry's rpm range] at or near[50 fps] the same velocity out of each of these rifles.
these are not a bunch of random 30 cal rifles they are a par of each
k-31's....ruger 308's, and a pair of savage 110's.
plus 2 30-30's. which were held to lower velocities to match each other as one is an ancient 94.


so is this a ceiling with a design or??????????
i have been able to do the h-v thing to 2300 fps but could only hold accuracy for 4 shots then it went, when the bbl was cooled i could hold 4 more shots.
is this it? if so.. i'll just stick to the 1950 and go shoot stuff,i just have to push a wet patch down the bbls when done and go home.

[Larry Gibson]

Runfiverun

There it is!

Larry Gibson

(carefull, you might end up with a new handle.....joe reloader;-) )

[joeb33050]

Some of you guys mention groups getting larger as you keep shooting, and hot barrels.
I think we should clean the barrel more often, and cool it. I cool it and then clean it iif I see accuracy degrading.
Here's some on cooling barrels, from ERRATA on the book site.
joe b.
BARREL COOLING
Pat Iffland
I think it's an accepted idea that hot barrels and cast bullets aren't the perfect combination and in a recent discussion with Jeff Bowles he mentioned he ran a small fan on his barrel between relays to cool it down. It sounded like a pretty good idea to me and since the
current cartridge/velocity combination I'm playing with (30x47-17 twist-170 gr LBT bullet-2575 fps) heats the barrel up real fast it sounded like a good idea.
After wandering around Menards for a while I found an air mattress pump that Coleman sells that runs on 4 D batteries (called the 4D for some unknown reason) that puts out a heck of a lot of air. In the plastic hose aisle I found a piece of 3/4 OD - 5/8 ID rubber hose that's a perfect fit for both the pump outlet and the action. So far I've tried the fit it in both my Stolle and a 98 Mauser action and the hose is a good fit in both so assume it'll work in any center fire action.
To test the thing out I picked up a barbecue thermometer with a 12 inch probe to insert in the barrel. I put O-rings on it because I didn't want to take any chances so the temp isn't actual barrel steel temp but air temp 12 inches in from the muzzle. I wanted to somewhat approximate shooting in a match so to start I fired 5 warm up rounds and then four 5 shot groups 7 minutes apart.
After the warm up and first two 5 shot groups I inserted the thermometer after 5 minutes and took a reading after letting the thermometer sit in the barrel the final two minutes. Temp was 135 degrees. I then shot my final two groups, ran the blower down the barrel for 5 minutes, followed the same test procedure of 2 minutes with the thermometer and air temp. in the barrel was 100 degrees. It stands to reason that the barrel would have been much hotter after firing 10 more shots so in my opinion the cooler does a great job. Price at Menards was 9 bucks for the blower and 5 bucks for 10 feet of hose. I've run the thing for an hour and a half with the cheapest D batteries I could find and it still puts out enough air to cool a barrel so overall not a bad investment if barrel heat is a concern. I've included a couple of pictures if you're interested.
Accuracy wasn't part of the test and the 30x47 is still giving me fits but I've also included a photo of the test target. Lower left was the warm up, top two are the first and second group, and middle and lower right are the last two. The flyer thing is something I have some ideas about and hope to have solved next time out but as you can see cooling the barrel doesn't seem to hurt and from what I've seen so far really helps in my case.
What got me going down this path is that in the second match I shot this gun in my first 10 shot group at 100 yds was .725, the second was 1.100. After a lunch and an offhand match my first 200 yd 10 shot group was some where in the 2.2 range and my second was almost 3 inches. Conditions were pretty bad but maybe it had something to do with heat. Time, and a small investment, will tell.







Pat



Junior Doughty
About a year ago I thought I'd get rich by making and marketing a barrel air-cooling device using batteries and a 5VDC computer fan and vehicle batteries and a 12VDC computer fan, which I installed inside PVC sewer pipe. Into the sewer pipe, I used PVC water pipe which slipped over the muzzle. I sealed the water pipe/barrel junction with something, maybe foam. So I made one of each and bought an infrared thermometer and did extensive testing.
The rifle used was a Win 94 20" octagon 30-30. The spot measured on the barrel was the hottest spot, which, IIRC, was a couple of inches forward of the chamber. I'd fire rounds in one minute intervals until the spot reached a target temperature, say 150 degrees since I can't remember the actual target temperature.
Target temp reached, I'd stop firing and measure the spot in one minute intervals and record the measurements. When the barrel cooled to air temp, I'd start firing again and repeat the process using the fan for cooling this time.
As expected, the barrel cooled MUCH faster with air forced through it. Actually, it was much easier to make a device to suck air through a barrel than to make a device to blow air through a barrel.
Then I wondered how fast the barrel would cool if I simply leaned the rifle against the bench with the action open and the barrel pointing straight up.
Guess what? The chimney effect cooled the barrel almost exactly as fast as did forced air.
As my bench was on my front porch I ran a hose into my air conditioned living room and forced cooled air through the barrel. That cooled the barrel much faster. However, here in Louisiana the high humidity caused much condensation in the rifle barrel when the cooled air hit it. Water actually dripped from the chamber.
In short, unless you live in a very low humidity area, forget forced air barrel cooling and simply open your rifle's action, point it straight up, and let the chimney effect go to work.

Junior Doughty on Cast Boolits

Joe Brennan
In the hot weather here in South Florida, some rifles and loads produce hot barrels.
Our course of fire is 15 minutes of firing followed by a period of about ten to fifteen minutes for target changing. I shoot 2-4 foulers and 10 shots for record in each 15 minute firing period.
On hot days with larger charges of slower powder the barrel is hot after the target changing period, hot enough to be uncomfortable to the touch.
I cool the rifle barrel using some plastic tubing, a funnel, and a bottle of ambient temperature water.
Pouring the water through the barrel and onto the ground cools the barrel quickly so that it doesn't feel a bit hot.
I've been doing this water cooling for a few weeks as the temperature at the range has been in the low 90s. Yesterday, 9/26/07, I brought a camera to the range to take pictures of the devilishly clever tubing-funnel apparatus. The barrel was at air temperature, no discernable heat, after the target changes; so I didn't do any cooling but did get a picture. As I left the range the radio lady announced that the Miami temperature was 74 degrees, very unusual for this time of year, and apparently cool enough to cool the barrel down without any help.


joe brennan

Jeff Bowles
Joe;
From my competition viewpoint, water is not practical.
First you are taking the barrel from one extreme to another, hot to cool very rapidly. Personally I don't think that kind of stress is good for the barrel.
Second you are introducing something into the barrel that could become trapped in the fine imperfections from the machining of the barrel. This may cause an adverse reaction such as a slight amount of hydroplaning.
Introducing any type of solvent to the inside of the barrel will remove any seasoning created by prior firings. I know that pouring anything liquid down the barrel will not result in 360 degree coverage so there will most likely be a small area at the top of the bore that will not get as wet as the bottom. The hassle of recollecting the liquid at the end of the muzzle takes time we just don't have when shooting matches.
The small fans I have are from Belkin and are available at most AutoZone stores for about $8.95 and run on a single D cell battery. One battery will last 2 days minimum under match conditions.
As an added bonus, since these fans amove air across the outside of the barrel, with a little aiming you can fore go the use of a mirage shield as the air flow is enough to disrupt the heat waves rising off the barrel.
Also as opposed to using a system that blows air down the inside of the barrel, this can be turned on and left on while you are shooting.
I find that using the external fans I can reduce the barrel temp at 7 inches from the chamber from 160 - 163 degress F to near ambient in around 7 minutes, the minimum time alloted between matches per CBA rules. I did this measurement using a K type thermocouple and a handheld digital display.
Jeff Bowles on the CBA forum

[Bass Ackward]

The RPM threshold is that point where the centrifugal force has an adverse affect on the unbalanced bullets intended path of flight. This is why imbalanced bullets (remember here they all are imbalanced to some degree) that are fired in or below the RPM threshold exhibit linear dispersion as the range increases. Imbalanced bullets fired above the RPM threshold will exhibit non-linear dispersion as the range increases.



Larry,

I have chosen to be scientific. I am going to bite the bullet and spend the money and re-barrel my 06 with a take off barrel 24" long. My load is going to be 38 grains of 4895 with the remainder of the 311291s that I have. I will test this load with the 24" barrel that may be worn so I suspect that these groups will be dramatically w o r s e than the 5" groups. (that Larry observed in his testing.)

Then I am going to take and cut that same barrel off to 16" and re-crown it. That will drop the velocity down with this load to 1800 fps. This will drop the RPMs down to into the magic zone number for a 10 twist which means that my groups size should improve dramatically if RPMs are the one true cause.

Any damage or unbalance to the bullet from pressure will be EXACTLY the same since it is the same bullets, in the same barrel, with the same load. The only thing we are going to do is lower the RPMs so that the unbalanced bullet falls within the zone of perfection and therefore my groups should improve dramatically if the RPM theory is true.

Do I understand the RPM theory now? Isn't this an air tight test of the RPM theory? It keeps everything EXACTLY the same except for RPMs ..... and pressure which has no effect on accuracy. (Larry's interpretation of the RPM theory.)

Larry, do you agree this is a perfect test? Will this not end all doubt one way or the other? I need feedback here, because I am not going to waste my time and money and scratch up my equipment only to have some body offer an excuse later. Does this answer / prove the theory?

[felix]

John, if you are going to do that chop affair, please do one for me. Cut barrel to exactly equal to 21+3/4. Do several tests there before going down to 16+0. This 21+ is what the BR boys say is the optimum for accuracy in terms of vibes (condoms) with about any bullet diameter. Well, personally I doubt it, but maybe it will prove out with 22 and 24 calibers without regard to your 30. ... felix

[Pat I.]

What's your velocity estimate out of the 24 inch tube?

[onceabull]

Sir: Do these "bench rest boys" include any qualifiers with their saying ?? Or can it be assumed that they talk specifically about bench rest diameter (weight) barrels ?? Onceabull

[runfiverun]

joe reloader? i like that..
except i really DONOT want the attention that the plumber guy got.......

we do however have a ton of joes here who really just wanna shoot a cast boolit in their rifle.
and they just wanna cast them from ww's or something like that.
they don't want to use fillers, or pistol primers,or anneal or turn necks.
hell most of them don't even wanna use g/c's.
and if they could just buy a good cast booit for 3 cents each they wouldn't even cast their rifle stuff.
all they really wanna do is shoot their deer rifles during the off season as cheaply as they can.
as well as they can, without too much load development.
that is the way i see it.

joe...b
some of my better loads [ groups ] have actually occured after the bbl has warmed up
the group shifts slightly and tightens up.
i attribute this to the lube in the bbl heating up all the way down the bbl and "evening"
the way it affects the boolit.
you know actually acting as a lube.
i have seen this occur time and again with my 308 and fully expect it to occur each time i use this rifle.

[mainiac]

John, if you are going to do that chop affair, please do one for me. Cut barrel to exactly equal to 21+3/4. Do several tests there before going down to 16+0. This 21+ is what the BR boys say is the optimum for accuracy in terms of vibes (condoms) with about any bullet diameter. Well, personally I doubt it, but maybe it will prove out with 22 and 24 calibers without regard to your 30. ... felix

Felix, its rude for butting in, but I know that my most accurate 6mm barrells have always been 25 inches (13.5 # h.v.) My L.V. gun has had barrells between 21&23 inches,and could never see a differance, and i also had some cut to 21.75,,,,, I think this is myth. Sorry for the intrusion.

[mainiac]

Ive read this hole string, and have never commented. ( I can tell when im out-brained!) One thing i would like to comment on though,,,,,,, In I.B.S. score-shooting, the 6ppc was the most accurate thing ever made by man, for years. Because of the bigger hole cutting capability, the .30 will score higher. I took years, but as of the last few years, the 30 B.R. cartridge has pounded the 6ppc in the ground. How did they do it? First, they went to light weight bullets, to lessen recoil, and then they started shooting slower,and slower twist barrells. Most barrells today are 17-18 twist ,for 110-125 gr. bullets. When i started shooting B.R., you either shot the 6ppc, or a full .308, with 14 inch twist, and 168,s. 6mm barrells are 14 inch twist........ The whole key is that these most accurate guns in the world, shoot barrells that are JUST marginally fast anuff to stablize the bullet. In my simple brain, that means that bullets shoot better, if they aint over spun.

[felix]

You both are not butting in, but adding info. I never was sure about any said barrel length being equal to anything static and concrete except by chance, because logic indicates the barrel needs to be chopped very gradually as to emulate the BOSS gadget. Prolly cheaper and easier to just install that boss or a lookalike. Anyway, if John is going to chop, he might as well play with different lengths on the way down to 16. ... felix

[Larry Gibson]

Bass

Sorry but no cigar. It is not airtight, not even close. The reason is simple. The same load in the shorter barrel cuts down on the time pressure curve. In other words you are changing the acclelleration. Everhting is not the same. There will be less accelleration in your 16" barrel. In my tests the barrels were relatively the same length and the actual time pressure curves (measured remember, not guestimated at) were basically the same. My barrels were all in excellent condition and I also shot 10 shot groups....are you? You're using a worn out take off.......? Actually the test might be unfair to you as the lands/grooves could much worn at the muzzle ed. When you cut back to 16" you are probably getting back into the best rifling that barrel still has. Also the rcrown you give it at cut off may well be much better than the crown it has at 24". Have you really though this through?

So, it is not "airtight", you are not keeping everything "the same". I do not agree that it is a "perfect" test. However it might be interesting to see your results. You also obviously don't understand the RPM threshold. I never said pressure never had any effect on accuracy, quite the opposite. I always have said that slower powder reduce the time pressure curve which lessons the damage done so there is less adverse affect from the RPM. Thus better accuracy potential. Apparently you do not understand that either.

It is not a perfect test as I've mentioned it has lots of problems. Let me suggest a simpler alterantive. Use your 30-06 with the barrel you have, no need to rebarrel to a "suspect worn" barrel. Using your remaining 311291 bullets load 5 shot test strings starting at 26 gr 4895 and work up to 38 gr 4895 in 1 gr increments (a 3/4 gr dacron filler will help a lot). Shoot those 5 shot test strings for group over the chronograph so we know the actual velocity of each test string. Report back the velocity of each 5 shot string and the group size (minus any called shots...I know you don't shoot any "called shots but just in case you can leave them out of the group size) of each 5 shot test string. We can do the math for the RPM.

After that test there is one other option if you really want to spend the money. After the above test rebarrel your '06 with a 26-28" barrel with a 14" twist. I'll send my mold back to you again and you can cast a bunch more 311291s. Then run the exact same test in the 14" barrel. Compare the results of that test with the 14" barrel to the above test with your 10" twist barrel. You need not compare the accuracy between the barrels as that comparison is not relevent. What you need compare is at what velocity was the best accuracy group for each barrel. It is alsmost certain you will find the velocity of the 14" barrel's best accuracy is going to be quite a bit higher than your 10" barrels best accuracy group. However, after then oing the math to find the RPM what you will find is the best accuracy groups for both barrels will be at pretty close to the same RPM.

Now let me mention your statement of "Will this not end all doubt one way or the other". Did we not hear this very statement from you once before? I recall you challenged me to conduct the linear vs non-linear test that you said would "end all doubt one way or the other" as to the validity of the RPM threshold. I agreed with you then that it would prove it one way or the other. I ran the test. The results were not what you wanted. It did indeed prove the RPM threshold theory. You recanted. You are still recanting (or is that "in denial"?). What makes us think you will not recant this time on your own "Will this not end all doubt one way or the other?"

Run your test if you must. It is your credability that is at stake here.

Larry Gibson

[leftiye]

Dern, now he's about acceleration, not RPMs. Smart on yer part Bass to ask first, saved ya a bunch o money!

So, again Larry, how about this "magical" thing that RPMs does to move a boolit out of it's path (deflect it) in the absence of - separate from yawing, not flying point on, air resistance, ect.? You DO understand that all centrifugal forces on a boolit are contained within the boolit itself proper, and cancel themselves out when it comes to deflecting the boolit don't you? Destabilize it , yes, move it out of its path, no. As I said, RPMs can do whatever it wants to a boolit, to include turning it inside out, and in the absense of air (resistance) it would still fly in the original trajectory (no deflection, perfect group). In space a full length rod fired fron a smoothbore would hit anything you pointed it at (mabe going sideways, but still hit it). Or, you could spin it as fast as you want, and it will still hit it. Higher probability of being point on is all.

I thought you were through here Larry? You talk about me not wanting to hear what YOU want to say!!! As usual you didn't answer me, and I was happy with that (no use talking to you), but You weren't through were you?

[leftiye]

FWIW, Maniac may just have it right. Better accuracy at lower TWIST rates. Is that because of fewer RPMs or because of less deformation though? (the ten cent question). For my money, overspinning only matters in an unbalanced projectile.

Larry shied away from Bass's test because he knew that the shorter barrel would exacerbate launch issues and produce all of the boolit damage the longer barrel did, yet only produce "safe" RPMs, while producing poorer groups, I suspect.

[felix]

No, leftiye, there is no maybe about it; Maniac has it exactly right. And, what you said is just as correct, in that less RPM means less deformation creation and/or less amplification of any existing static imbalance. ... felix

[crabo]

Ya'll keep this up! I am beginning to understand it.

[runfiverun]

john; you also know that your muzzle pressure will be much higher with that 16" bbl
and you know larry's mold isn;t even a close fit to your throat.

please, at least be a bit fair here, remember i did the linear test also the same day.
maybe with results that could be predicted true.
but the truth is in here somewhere. does it or not?

[Larry Gibson]

leftiye

"You DO understand that all centrifugal forces on a boolit are contained within the boolit itself proper, and cancel themselves out when it comes to deflecting the boolit don't you?"

No, I do not understand that because it is not true. You seem to think only in terms of "deflection" such as you oft mentioned air resistance. The adverse affect of the centrafugal force from RPM has nothing to do with "deflection". Obvious to everyone here that you won't listen to me not believe me. Again, I'll refer you to the Hornady manual as it has the simplist explanation. Unfortuneately you refuse to read it therefore you fail to understand.

Also you make false assumptions. I did not "shy away" from Bass's test. I was rather direct with him. Nothing shy there at all. I also know no such thing as you say I do. The "launch" issues favor better accuracy with the 16" barrel. Just ass backwards from what you think. I informed him of that. I also told bass to run his test if he wished. You seem to ignore that as you ignore most factual things.

Some are beginning to understand the RPM threshold; that is good.

Larry Gibson

[Pat I.]

No, leftiye, there is no maybe about it; Maniac has it exactly right. And, what you said is just as correct, in that less RPM means less deformation creation and/or less amplification of any existing static imbalance. ... felix

Felix what you said above is exactly what Larry's been saying all along.

To achieve BEST accuracy all bullets, but especially cast, are twist limited. Putting all the theory and conjecture aside all I need is for one person to match let alone better the accuracy of a bullet going 18 or 1900 fps, with a suitable powder, in a 10 twist 30 caliber barrel with a bullet going 24 or 2500 with any powder and I'll scratch the RPM theory off my list of things I believe to be true.

There's been numerous references to "Joe Caster" in this thread and my question to you is exactly what are you guys doing that's so different from everyone else?

[Geraldo]

Ya'll keep this up! I am beginning to understand it.

I'm glad somebody is. I read all three pages of this and all I got was RPM=***?

[Larry Gibson]

Geraldo

This perhaps is not the best thread to attempt an understanding. There were two other major threads regarding this topic that probably will provide a better understanding or possibly a greater confusion. There are a couple members who appera to be arguing for the sake of arguement which adds to the confusion.

The concept of the RPM threshold is simple. Perhaps Pat I says it simplist; Best accuracy for most cast bullets in a rifle will come at a certain RPM rate governed by the twist. The faster the twist the lower the velocity will be for that "best" accuracy. Conversely, the slower the twist the higher the velocity will be for "best" accuracy. Using the example of the 10" twist barrel of .30 caliber in Pat I's above post is correct in that "best" accuracy will come in the 1800-1900 fps range. With the 6.5 Swede the velocity of where "best" accuracy will be found is lower because the barrel twist is faster. The velocity of a 12" .30 caliber rifle where "best accuracy can be had is higher because the twist is slower. A 14" twist .30 cal has an even higher velocity level where "best" accuracy can be had also because the twist is slower than either the 10" twist or the 12" twist.

The reason is simply that the twist rate and velocity control the RPM. The faster the velocity in a given twist the higher the RPM. If we manage to keep the RPM somewhere between 120,000 and 140,000 RPM we will find the "best" accuracy with cast bullets in our rifles. Above the level of RPM where we found "best" accuracy the centrafugal force of the RPM will have an adverse affect on the bullets flight and accuracy will decrease. Should we want to exceed the RPM threshold the amount that the accuracy decreases is subject to special casting/loading techniques and certain designs of cast bullets. Acceptable accuracy over the RPM threshold of a given bullet in a given twist can be had but will have practical limitations that the "best" accuracy loads found within the RPM threshold do not have.

Larry Gibson

[felix]

Pat, Larry and John are both correct at the same time, and that is where the confusion is, or is where it becomes difficult to formulate a conclusion using the verbiage as stated from both sides of the fence. It appears that John likes to place emphasis on internal flight, while Larry places his emphasis on external flight. As Frank Sinatra would say, they go together like a horse and carriage. ... felix

[Echo]

I have a 'Newbie' question - What effect (if any) does boolit hardness play in the mix? may a harder boolit be driven above the 1800-1900 threshold and still be asaccurate, or moreso?

I can see where the tensile strength of pure lead, or mildly alloyed lead, may be such that it will be defeated by centrifugal force above a certain RPM. If the boolit is HT to a BHN of 30, will that show up as higher velocity being capable before groups start to enlarge?

[felix]

Yes, provided everything is maintained as exactly as before. A hard boolit deforms less when it hits the lands, giving less distortion on the ogive front. By the same token, a hard bullet might not exit the barrel as uniformly as a softer one would. Why? Because the force of the expanding gas tends towards the center of the projectile once the projectile is moving, leaving the tail more as cast instead of made exactly round. ... felix

[Pat I.]

It appears that John likes to place emphasis on internal flight, while Larry places his emphasis on external flight. As Frank Sinatra would say, they go together like a horse and carriage. ... felix

Felix, What's going on in the combustion chamber and the 22 inch or so trip down the barrel is all theory while on the other hand holes in a piece of paper are facts and external flight determines where thay end up on that paper so I'll stick with the holes. Like I said before someone show me targets that match a 30 caliber in a 10 twist going around 18 or 1900fps with some that out shot them going 24 or 2500 fps and I'll gladly throw the twist limited idea out the window.

I've said in another thread it's been my experience and a lot of other really good shooters I know that in a thirty caliber starting with a 10 twist at around 1850 fps you can gain about 100 fps more velocity and still maintain BEST accuracy for every inch reduction in twist. Smaller than 30 cal and you can run faster RPM, larger requires slower. Which is why you see 7 and 9 twists in the 22 calibers and 18 and 20 in the 45s

My 2 cents on the subject.

[leftiye]

Obvious to everyone here that you won't listen to me not believe me. Again, I'll refer you to the Hornady manual as it has the simplist explanation. Unfortuneately you refuse to read it therefore you fail to understand. L.G.

Sure Larry, I do listen to you not believe yourself all the time.

So which Hornady manual is this supposed to be in? My third edition had a section about accuracy, but it said nothing about twist, nor RPMs.

So c'mon Larry, just how does RPMs deflect a boolit? You wrote about deflection in your response to me, but you misinterpreted it. Deflection is by definition moving a projectile from its path to another trajectory. Before you can get inaccuracy, one or both of two things must happen. The first possibility is that the gun launches sucessive boolits on different paths. The second is that something moves the boolits from their original path (deflects them). You claim that this RPM effect does not depend on deflection in the air, and that it is distinct from launch and deformtion problems that launch boolits on varying paths. So just explain to us please how it does it.

Again the spinning boolit is self contained. There is nothing available for Newton's "equal and opposite reaction" to come from if only rotation of the boolit is operating. You can spin a boolit as fast or slow as you want, but air resistance acting upon instability (boolit being not point on) is the only force that I can see in the situation that has any chance of deflecting a boolit from its path.

[Pat I.]

"Q: Why do you recommend the slowest twist?
A: Spinning a bullet faster than necessary can amplify any inconsistency in the bullet. Since we use J4 jackets you can shoot Berger Bullets in faster twist than what is listed. We list the slowest twist rate needed because we want to squeeze every bit of accuracy out of a rifle."

The above is copied from the Berger Bullet website. In case you don't know what a J4 jacket is it's a jacket for making bench rest bullets that have 3/10,000 or less run out and is used for making some of the most accurate bullets in the world. I think I've read in the past that Sierra Match Kings run about .0007 or so on jacket consistency and they ain't no slouches but that 3 or 4 tenths makes a big difference.

That being said I don't care if you're casting from a golden pot with a platinum mould we're not going to get near the consistency of a bullet like this and have to accept the fact that faster RPMs are going to degrade accuracy.

[wiljen]

Gents, just a reminder to keep it pleasant. I know this is a topic some of you are very passionate about and your answers sometimes get a little rough based on that passion. Please refrain from posting comments about other users regardless of how different their opinions may be.


Thanks,
Will

[45 2.1]

RPMs have little effect, except for rotational stability out side the barrel. Whether your boolit will shoot good or not is determined by its passage for the case neck to the point the base of the boolit enters the rifling. Its either concentric with the barrel center or not at that point.

[felix]

Bob, no question about that! That is where 99.99 percent of guns on this board fail first and foremost. ... felix

[Larry Gibson]

Leftiye

So which Hornady manual is this supposed to be in? My third edition had a section about accuracy, but it said nothing about twist, nor RPMs.

I'm not at home right now so I will tell you which Hornady manual later this evening. It is in the article up front on accuracy . The information is about center of form, center of gravity and center of spin and how they relate to each other and affect the accuracy of the bullet in flight. The request you read that Hornady article was in response to your inability to grasp how those 3 items relation to each othe affect accuracy. That is what I told you to read about, never said it was about "twist" or "RPM"

So c'mon Larry, just how does RPMs deflect a boolit? You wrote about deflection in your response to me, but you misinterpreted it. Deflection is by definition moving a projectile from its path to another trajectory. Before you can get inaccuracy, one or both of two things must happen. The first possibility is that the gun launches sucessive boolits on different paths. The second is that something moves the boolits from their original path (deflects them). You claim that this RPM effect does not depend on deflection in the air, and that it is distinct from launch and deformtion problems that launch boolits on varying paths. So just explain to us please how it does it.

You are only considering "deflection" as an only possibility. The adverse affect of too high RPM is not "deflection" as in the bullet being moved by air resistance or the wind. There are more of Newton's Laws than just that one and others' apply. Consider cenrafugal force; if you twirl a weight on the end of the string it pulls the string sraight and keeps it taught. The faster you spin the wieght the harder you must hold onto the string. If you move your hand in a cirular motion while still spinning the weight the weight will follow that circular motion only it will be traveling farther in a much wider arc.

Imagine the hand to be the center of spin. If you hold it still then imagine the hand to be the center of form, the center of gravity and the center of spin. When you move the hand in slight circular manner the center of spin is no long at the center of form and the weeight not only goes around but is not going in a circular motion. The larger and more iregular the motion of the hand the more eccentric the path of the weight will be. Same thing with bullets. The twirling motion at the end of the taught string is the stability caused by a sufficient amount of RPM. The irregular path of the weight caused when we move the center of gravity and center of spin away from the center of form. That "irregular motion of travel is what we are talking about. It is not instability of the bullet either.

Again the spinning boolit is self contained. There is nothing available for Newton's "equal and opposite reaction" to come from if only rotation of the boolit is operating. You can spin a boolit as fast or slow as you want, but air resistance acting upon instability (boolit being not point on) is the only force that I can see in the situation that has any chance of deflecting a boolit from its path.

Read the answer above and the section in Hornady's manual. Then perhaps you'll understand. Try to go into it with an open mind. If not then you are just argueing.

Larry Gibson

[Larry Gibson]

45 2.1

RPMs have little effect, except for rotational stability out side the barrel. Whether your boolit will shoot good or not is determined by its passage for the case neck to the point the base of the boolit enters the rifling. Its either concentric with the barrel center or not at that point.

You're thinking here is quite incorrect and is the basis for errors in thinking on this subject. I'd also suggest tht you read the article in Hornady's Manual on accuracy of bullets. Inside the barrel the center of form and the center of spin do coincide as the barrel dictates both. However the center of gravity may not coincide with either of the others. It is during flight of the bullet that the centrafugal force of the RPM can move the center of spin away from the center of form if the center of gravity does not coincide with them. The center of gravity most often does not lie with the centers of the other two in the barrel and the bullets do not fly perfectly concentric. This is why bullets disperse in flight and shoot groups instead of all going through one hole. Read the Hornady article, then perhaps you will understand.

Larry Gibson

[Pat I.]

So c'mon Larry, just how does RPMs deflect a boolit?

It doesn't it disperses them and the faster you spin it the more it'll disperse. Relating to the subject at hand only a bullet doesn't only yaw and go to sleep once it leaves the barrel it spirals because now it's spinning around it's center of gravity instead of it's center of form. Sort of like looking down the center line of a spring. The faster you spin it past a point the more it'll spiral leading to more dispersion in your groups. There's numerous articles describing how center of gravity vs center of form is one of the reasons bullets don't go into the same hole.

I'll agree totally that bullet fit, loads, powder and all the other things that make up a good cast bullet load are of the utmost importance but that's not what's being discussed here.

[Tiger]

Hallo

Yes yes I know long time. I see the rpm still alive. I wish to say this since it was mentioned about bullet going to sleep. New studies about over stabilization have come about recently. One is about the going to sleep. They find this. They find the higher the rpm the longer distance to take the bullet to go to sleep. They say with normal twist most bullets go to sleep/stabilize before 100 meters. They are saying now that very high rpm bullets can take up to and over 150 meters to sleep/stabilize. This makes me think way back to Larry Gibson rpm test. Maybe Larry if you move targets different distance for the 10 inch twist rifles you may find accuracy will improve. You will have to experiment to what distance that is. First time maybe move target 110 meters. You get the idea. They also say that over stabilization not looked upon so negative now. I see more rifles in faster twist for say 22 calibre. Example is for 22-250 now see 9 twist and rifle listed as competition target rifle. I think too varmint rifle. Then I think most don't use heavier bullets in that calibre for varmints so manufacturer is in ways insuring this fast twist will shoot lighter bullets with much degree of accuracy to.

Ralf

[leftiye]

Good to hear from you Tiger!

[45 2.1]

You're thinking here is quite incorrect and is the basis for errors in thinking on this subject. I'd also suggest tht you read the article in Hornady's Manual on accuracy of bullets. Larry Gibson

Obviously, you don't agree with Felix or me. There is a difference between reading about these issues and doing them correctly. I know how to get accuracy with bullets, BTDT and its boring now. The issue here is accuracy with boolits, something you need to investigate further for yourself. I already know how to do that slow and fast.

[runfiverun]

hey tiger, good to hear from you again.
and now i think you are beginning to see what larry is/was saying.

[Larry Gibson]

Tiger

I already moved them to 200 yards for the linear vs non-linear test for Bass, remember? The results were the same. The 200 yard group for the load that was within the RPM threshold was 4.5". The 200 yard group for the load that was well above the RPM threshold at 2400+ fps was 14.5". The test was done with the 10" twist rifle and using 311291 in case you forgot. Bass said that test would prove or disprove the RPM threshold theory. The test proved the theory and Bass didn't like that so he recanted. What else can I say but we've already covered your suggestion and it proved the bullets weren't "going to sleep" but actually had their accuracy adversely affected by the RPM.

Larry Gibson

[Larry Gibson]

45 2.1

"The issue here is accuracy with boolits"

No it isn't. The issue here is the best accuracy with cast bullets in rifles. It is what you fail to understand. Many of us shoot cast bullets accurately "slow and fast". The point is the best accuracy will be under the RPM threshold for that bullet/load. Why don't you run the simple test I suggested Bass run. Shouldn't be difficult for a reloader of your self stated ability. Pick an accurate .308W or 30-06 with a 10" twist barrel. Load some 311291s in 5 shot strings from 1700 up through 2500 fps in 50 fps increments and shoot each group over a chronograph so we'll actually know the velocity. You pick the powder, you pick the lube, you pick the primers, you pick the GCs, you pick the bullet size, weight the bullets if you want, neck size the cases or load them anyway you want. Just shoot the groups 50 fps (+/_ a few fps) apart from 1700 up through 2500 fps. Then let's compare the accuracy of all the test strings and compute the RPM. So show us what you can do.

Larry Gibson

[leftiye]

So, Larry boolits and cast bullets aren't the same thang? FWIW, I doubt you've got any clue as to what we understand, or don't understand.

While ye're at it let him use a boolit that has a chance at high velocity. You might be surprised at what happens. Your whole test was conducted with that boolit, and it precluded any other results than the ones that you wanted. (Though I'd say that Bass' groups at 2300 fps (?) weren't too bad.)

[missionary5155]

Good morning
#1 I have re-read this thread several times and appreciate your burning all the powdr to do it. Internal ballistics is FACANATING !

#2 Is there a basic (general) formula that indicates at what RPM we can expect a boolit of "x hardness" to begin to fail to properly grip the rifling and merrily skip its way down the tube ? I understand rifling shape, depth, width, twist... all play into this.

#3 I have "heard" stories of boolits that were spun beyond structural integrity flying apart while headed down range. The story NEVER included how much lead was deposited in the bore. The story was usually about some .22 cal superfast laser blaser. The stories may be true ??? I have not been present to witness this happening.
Maybe there is no relationship between a boolit self destucting due to centrifical forces outside the barrel and not holding onto the rifling.... But just for my curiosity is there a relationship... I find it hard to imagine a boolit can spin so fast as to fly apart yet not leave a nasty silver trail in a barrel (unless it was PP or sheilded somehow).

[Bass Ackward]

Bass

Sorry but no cigar. It is not airtight, not even close. The reason is simple. The same load in the shorter barrel cuts down on the time pressure curve. In other words you are changing the acclelleration. Everhting is not the same. There will be less accelleration in your 16" barrel. In my tests the barrels were relatively the same length and the actual time pressure curves (measured remember, not guestimated at) were basically the same. My barrels were all in excellent condition and I also shot 10 shot groups....are you? You're using a worn out take off.......? Actually the test might be unfair to you as the lands/grooves could much worn at the muzzle ed. When you cut back to 16" you are probably getting back into the best rifling that barrel still has. Also the rcrown you give it at cut off may well be much better than the crown it has at 24". Have you really though this through?

Run your test if you must. It is your credability that is at stake here.

Larry Gibson


Larry,

Thanks for making my point. See here is exactly what I mean. The excuses come out. Thanks for not wasting my time.

I took the 16 grains of 2400 load that has worked across, (dare we say hundreds of thousands)quite a few barrels, and you say I didn't do enough work. And what is lost on you is that I matched the accuracy of that proven load at a higher velocity that the RPM was 165,000.

Then I quoted where groups of a dramatically large size exhibited NO RPM effect out to 100 yards. 100 yards was exactly double 50 yards. You said ALL INACCURACY is due to RPM. Something else was responsible for the inaccuracy and it was excused away.

Yet my credibility is at stake? RPMs didn't effect me because .................... Or my test wasn't scientific enough to invoke the interest of the RPM monster.



One more try Larry. Thanks for me not wasting my time. I knew that there would be some reason that the theory wouldn't hold true for me. And it is my credibility?

I went hunting this weekend. Found something disturbing. My shot gun exhibits the same RPM effect, my groups open as distance is increased and those pellets AREN"T even spinning. No rifling, no RPM, and I have the RPM effect. Rifling is put in a barrel to allow stable flight through air to prevent the RPM effect.

When you take a (1) worn barrel, or (2) an extremely fast twist rate, or (3) a softer bullet you lose the ability to make a good launch. At that time, the velocity rotation required is insufficient to establish stable flight so air effects it. The faster the bullet, the faster the air and the more force it has to act upon your slug. Happens to jacketed (harder skin with better grip on the rifling) too eventually. That's why you need rifling in a barrel even with jacketed and why worn barrels must be replaced. They can not launch properly enough to avoid " air " disturbing their flight.

So, can you over spin something? Yes. If the over spin affects your ability to launch properly that air negatively affects your slug. The faster the air, (higher the velocity or worse the BC) the more terrible the effect. So inaccuracy really has nothing to do with RPM. It is RPM that we need to correct our failure to launch and stabilize because of the damage we do.

Now is there an RPM effect at all? Absolutely. But this is a slow velocity phenomenon. When a slug slows to the point that the forward velocity and the rotation are inadequate to maintain stable flight, it exhibits the shot gun effect or RPM effect caused by air. The key is to streamline your slug (not so with most cast) and balance it better so that it loses less velocity and makes this occur PASSED the range that you intend to shoot. If you can't run a slug faster, you need to spin it more and you either need taller rifling or a harder slug to do it.

The reason we don't shoot one hole groups isn't RPM. It's the fact that we can't launch each slug the same so that it is affected by air the same. Ballistics 101.

So yes I don't understand the RPM effect.

[Bass Ackward]

What's your velocity estimate out of the 24 inch tube?


Pat,

This was 2100 fps out of my gun. 16" was a drop only to 1750. (Quickload predicted) Since the slug doen't fit my gun at all, this should show improvement. A slower powder would make the drop more dramatic and push the high end, but this was Larry's load.

If you read my post above then the test is not needed. Lower velocity will have an improved effect on accuracy because there will be less deflection. Not becausee there is less RPM.

[Bret4207]

Someday I want you guys to discuss the classic Ford vs Chevy vs Dodge thing..........:holysheep

[Bass Ackward]

John, if you are going to do that chop affair, please do one for me. Cut barrel to exactly equal to 21+3/4. Do several tests there before going down to 16+0. This 21+ is what the BR boys say is the optimum for accuracy in terms of vibes (condoms) with about any bullet diameter. Well, personally I doubt it, but maybe it will prove out with 22 and 24 calibers without regard to your 30. ... felix



Felix,

To do this would be inconsequential with one barrel. It would require many to achieve a statistical significance. And I think the fact that 22" is fairly standard in the industry tells you that at least the guys putting their name on the product believe it is true.

But what is true for jacketed, isn't necessarily true for cast.

The benchrest cast bullet crowd goes about it all wrong in my opinion. If the damage is done at the start, and the object is to launch as gently as possible, then a sharp shouldered, straight sided case and heavy per caliber bullet is not the way to go. You would need a case volume to bore ratio capable of doing that while at a light bullet weight per bore diameter maintaining good ignition with a long neck to control heat. The barrel would have to be long enough to burn what you chose and produce the velocity desired with it. In my mind, that barrel length goes beyond what is in use today.

The need to run straight sides and a sharp shoulder and heavy for caliber bullet just requires an even slower powder and an even longer barrel to achieve the same gentle start and launch.

[Bass Ackward]

Someday I want you guys to discuss the classic Ford vs Chevy vs Dodge thing..........:holysheep

Bret,

Many intelligent people try to predict the weather and tell you why. Look how many people follow that everyday. The only job that you can be wrong better than half the time and still keep it.

Some day this will be worked out too if the guns aren't taken first.

[Pat I.]

The benchrest cast bullet crowd goes about it all wrong in my opinion.

Bass, And I guess you'd be entitled to that opinion once you started showing up and beating everybody [smilie=1:. Do you even know what the cast bullet BR crowd is using or the results they're getting? Go take a look at the website sometime and look at the match reports and national records. They're pretty amazing especially considering that they're timed events and you don't get to pick the weather conditions you want to shoot in.

[Pat I.]

Pat,
If you read my post above then the test is not needed. Lower velocity will have an improved effect on accuracy because there will be less deflection. Not becausee there is less RPM.

Bass, Are you saying lower velocity bullets will be deflected less by air (wind)? I also have a question about your references to taller rifling, what exactly is taller rifling and where do you get it? Besides Microgroove in a 30 cal most if not all are in the .004 range.

You really should go ahead with conducting your test if you already have a worn out barrel sitting around.

[Larry Gibson]

Folks

I am done for sure this time with Bass, 45 2.1 and leftiye on this subject. I have tried to use reason and have conducted test after test. They do not understand because they do not want to understand. Now even Bass has the audacity to say "The benchrest cast bullet crowd goes about it all wrong in my opinion"! I gave him no excuses regarding his last offer of a test. I told him up front that it may be in favor of disproving him. I gave him a simpler and less expensive alternative but in the end I told him to proceed with his test. He mentions the load he chose of 16 gr 2400 as being a great load for 311291 yet I think we really all know that the most accurate load with that bullet is around 20 gr. There is another thread going regarding the accuracy of that 20 gr load. !6 gr of 2400 with a 311291 is only going to give 1450-1500 fps or so and ignition is not going to be as efficient as with a few more gr of powder. I told him to take a powder and load it from 1700 to 2400+ fps. If he wants to use 2400 then 18 – 29.5 gr will take him from 1600 fps to 2300 fps. He could try that and would quickly discover the RPM threshold as everyone else has. But he won’t, he would rather argue.

Leftiye obviously just wants to argue. The point in case being his last post; Bass chose to use the 311291 bullets he cast from my mould. Bass chose to use those to prove me wrong. Everyone has read this in this thread and the previous threads. Also everyone here who has followed this discussion knows that I used 3 different bullets in my “whole test”. Not just the 311291 that leftiye is arguing about. I even used Bass’s LBT bullet (the one leftiye is insinuating I should “let” Bass use) as Bass sent me a bunch. I also previously reported excellent accuracy with that bullet at 2300-2400 fps but accuracy was still “best” down in the RPM threshold under 2000 fps. Bass even agreed that accuracy was easier down there. Yet here leftie is still arguing about “accuracy weren’t to bad” at 2300 fps. I have stated over and over again to these 3 and everyone else that what we are talking about is where best accuracy can be found. Pat I has reiterated that very thing on this thread a couple times. Leftiye does not listen, he just argues.

And then there is 45 2.1. What can I say other than the rest of us are so incompetent and know so little about loading and shooting cast bullets that only he can shoot them well “slow and fast”. He, like leftiye not only don’t want to listen to us here but the refuse to read other written works that explain the principles we’re discussing. He also still thinks The RPM threshold is just about developing an accurate load. He can not understand that is not the case no matter how many times I and others explain it to him. I and many others have developed “accurate” cast bullet loads at higher velocity but still find the “best” accuracy to be in or under the RPM threshold. The RPM threshold is not about developing and accurate load, it is about best accuracy. That is not a difficult concept to grasp yet 45 2.1 still just argues.

So you see folks, I have tried to reason with these gentlemen as others have. I don’t ask that they agree with me but I do ask that they understand. They don’t, they only argue. So with that I shall discontinue any further discussion with then regarding the RPM threshold. I will continue to discuss it with anyone else who wants a discussion and not an argument. Again, you don’t have to agree but please present facts backed up by tests. Thanks to all for their time.

Larry Gibson

[Larry Gibson]

Pat I

Very interesting questions! I've often pondered the idea of taller rifling (smaller "bore" and deeper grooves). The idea that it gets a better "grip" on the bullet and prevents "stripping". However I think there will be a break over point where the damage done to the bullet creating more imbalance which of course the RPM will have a greater adverse affect on. Also I've shot some cast bullets at pretty high velocity out of rifles with .004" rifling and found no evidence of the bullets being stripped by the rifling. (handgunners - revolvers are another story so please don't tell me about it, ok, we're talking rifles here)

Now I am also wondering how a longer neck "controls the heat" and how that improves accuracy, do you have any idea?

Larry Gibson

[Pat I.]

I don't understand the taller rifling concept myself and even the much touted Ballard Rifling is nothing more than a 6 groove cut rifled barrel with a nominal .308 groove .300 bore. I don't even know if bullets do strip normal rifling or if more grip would help if they did. I'd imagine though that if the load was so far out of whack that it could strip with a .008 grip on the bullet another few thousandths wouldn't help much. Can't think of a better gripper than a two groove but I don't think they're known for their accuracy. Of course they can made to shoot pretty well but since they were designed to cut down war costs and I don't see anyone making them anymore I don't believe they're the best form of rifling.

I don't know about the long neck theory since powders are progressive and most rifle powders are still burning when the bullets in the bore. Some of the most accurate cartridges known to man have relatively short necks, and that goes for jacketed and cast. The only really long necked cartridge that I can think of is the 30-30 and that's only because the thing doesn't have a throat.

The first BR gun I chambered was made by running a 30-06 reamer in short, cutting off a 30-06 die, and forming cases out of 35 Rem brass. I used the RCBS 165 Sil bullet and the case ended up with a pretty long neck, a tapered body, and a gently sloped shoulder. It didn't shoot any better or worse than anthing I've used since.

One final thing. I don't think I'm a slouch when it comes to cast bullets and have done a lot of experimenting but sometimes I don't know what the heck people are talking about on some of these threads and this one is a good example. I've never heard the term "launch' used in a gun discussion but think I have it figured out and that's just one example. I think you'd get a lot more participation in some of the topics if you left out a lot of the "Scientific" talk and stuck to good old gun talk.

[Tiger]

Hallo Larry and I mention hallo to Felix for welcoming me back.

Hey Larry thanks for not writing me off along with others. I am going to type some from article american military man give me. This way I can not mess up English too bad.

First, let's look at truths about what overly fast rifling twists can do: 1. Varmint bullets with thin jackets can litereally rip apart in flight if the twist rate is too fast. 2. The effects of a flaw within the bullet are magnified and groups open. 3. The bullet "goes to sleep" farther from the muzzle. The first seldom entered the equation until some rifle makers changed the twist in their .223 Remington rifles from the original 1:12 to the 1:7 that the U.S. military adopted for the 5.56mm NATO round. Varmint bullets prime attribute----the thin jacket----simply could not stand up to a 40 to 50 percent increase in rotational forces. We're talking the big-game rifles, so this argument doesn't usually apply to these more robust bullets.

The second truth is real, but those defectes it requires are getting very rare as bullet manufacturing processes. With modern technology, bullets are incredibly concentric, and high concentricity negate adverse rotational effects.

The third relates to a known characteristic of spin-stabilized bullets----they "wobble" slightly as they leave the tight confinement of the rifled bore. Spin eventually corrects the wobble, usually in the first 50 to 80 yards, and the bullet settles into stable flight, or informally, it "goes to sleep". However, long bullets fired at high velocities from fast-twist barrels may not go to sleep until more than 100 yards from the muzzle (I mention this in my post from other day).

This explains why some very experienced riflemen say that the 7mm Shooting Times Westerner often shoots similar group sizes at both 100 and 200 yards. At 100 yards, the bullet still has a little wobble that is not quite damped by the spin.

More to come Larry...stay with me.

Ralf

[Pat I.]

The second truth is real, but those defectes it requires are getting very rare as bullet manufacturing processes. With modern technology, bullets are incredibly concentric, and high concentricity negate adverse rotational effects.Ralf

I'm not Larry but if you don't mind I'd like to comment on this part of your post. 3 or 4 ten thousandths of an inch in jacket concentricity makes the difference between a match and standard rifle bullet and a difference on how they shoot.

I think it's pretty big odds that we're getting anything like that with cast bullets.

[Larry Gibson]

Tiger

I'm with you and everything you're talking about is pretty much correct. Only disagreement I have is when the concept of bullets "going to sleep" came about. It was discussed back in Elmer Keiths day (even before my time!) with the .333 OKH cartridge. I lalso learned of it from high power shooters who were beginning to shoot 190 -250 gr match bullets from 8" twist barrels. That was quite a few years before the twist got quicker ay 1-7" for the 5.56 NATO. Other than the historical part we are trackin'. Have you ever watched tracers (particularly .50 cal) fired at long range? If you have you'd have notice that they begin to spiral after a while. They are still stable and fliying point foreward but are spiraling. This is caused by the trace material burning out and the bullets becoming imbalanced. The RPM has the same adverse affect on them as it does with cast bullets only at a lower velocity. That is the spiral effect and has nothing to do with the bullet "going to sleep".

I also agree with Pat's post to you. We are not getting any where near that kind of concentricity with our cast bullets. Many years ago I had a new 2 groove M1903A3 barrel. The 2 groove barrels were touted as just the ticket for cast bullets. I had it set back and chambered to my own idea of a perfect cast bullet cartridge. The idea was to drive a 311284 at 2100-2200 fps using a medium powder like 4895 with 100% loading density. My cartridge probably looked a lot like Pat's except I stuck with the .308 case. The case has an '06 lenght neck with the shoulder set back and is 2" long. It does right at 2200 fps with 100% loading density of IMR 4895 in the 22" 2 groove barrel with a 311284. Since I had a short stiff barrel, a short squatty case with a long neck and the 2 groove barrel i was expecting great accuracy. Didn't happen. I got 3-4 MOA. I switched bullets, powders, primers, alloys, etc untill I was blue in the face. Accuracy was right at 1-1.5 moa when the velocity was 1800-1950 fps. That was exactly what I was getting in a standard '03A3 with 2 and 4 groove barrels. It also was exactly what i was getting with my .308Ws. I was stymied for quite a while. Then I ran across an article that discussed RPM and how cast bullets in 10" twist '06s vs slower twist rifles didn't do well above a certain level of RPM regardless of the velocity. It then dawned on me that all of the rifles I had been using, including the 2 groove barrel had 10" twists. All gave very good accuracy between 1800 and 1950 fps. All began to lose accuracy above 1950 fps. It was then that I began investigating the adverse affect of RPM. I've not found a single case of shooting cast bullets in rifles where the best accuracy didn't come in or below 120,000-140,000 RPM. That is where the RPM threshold lies most of the time. There are exceptions as I have reiterated numerous times in the past but very, very few with the regular type cast bullet most of us use in the rifles of 12" twist or faster.

Larry Gibson

[Tiger]

Hallo Larry again...good .. we are talking. I will continue where I left off on article. Sorry I can not always be on.

There is more concept that a too fast spin will always increase group size when no other factors are at play. (this one makes me think you Larry) Like other shooting conceptions, I find that this one likely goes back to military experience, in this case, artillery. One of my fellow engineers at Speer was a former U.S. Army artillery officer, and he was very aware of twist-rate factors; one clearly revealed the source of the "too much twist misconception". (Pay attention to that Larry "too much twist MISCONCEPTIONS")

In artillery, high-angle fire sis the standard fireing model. Some field pieces like howitzers may fire with the tube eleveated to 40 to 70 degrees. For decades, the "fuse-in-nose" design ruled nearly all projectiles for the land-based artillery, requiring contact detonation. The projectile had to hit the ground fuse-first or the main explosive charge may not ignite.

High-angle artillery fire required critical twist-rate considerations so that the projectile would turn nose-down after reaching the top of its very high arched path. It turns out that too fast a twist rate left the projectile spinnning like a top at the peak of the trajectory where it's vertical velocity approached zero. Typical of gyroscopic stabilization, the shell tried to stay as it was when fired: nose higher then base. As gravity moved into the driver's seat and the projectile started down, its nose tended to stay above the trajectory line instead of leading the way with the all-important fuse ready to hit first.

Let's get practical again. There are few if any sport-shooting conditions that qualify as high-angel fire to the aritilleryman. Even shooting a .45-70 cast bullet at a 1,000 yard target is techinically direct fire. The elevation is only a few degrees compared to the whopping angles used in howitzers. As long as you are not shooting thin-jacketed bullets and can deal with bullet "sleeping" farther out than usual, don't get too hung up on the "perfect twist" for big-game rifles.

Jumping ahead in the article:

Be aware that changing to a longer high-tech bullet could push you close to the stability boundary. Realistically, the only modern cartridge where I foresee a problem is the .308 Win., where some rifles have a 1:12 twist barrels. If you are shooting 180 grain conventional spitzers and change to an all-copper version, you may learn more than you want about stability problems.

Ok Larry, me again, that give you something to think about. I am of the belief that over stabilization is a myth for jacketed bullets. I am just not seeing it myself and what friends are shooting. I think like you and others mentioned cast bullets are not perfect. This and getting damaged getting into the bore is much amplified by faster twists. I would think then that there rpm threshold for bullets that are anything but perfect. But I would not say that fast twists cause inaccuracy.

Larry...think to cast perfect as can cast bullets. Weigh them do all tricks there are before loading. Instead of loading into cartridge case let us push them as perfect straight possible and gentle possible into the bore. Then we load charged case behind it in safe manner you know what I mean. You think this help accuracy?

Ralf

[Larry Gibson]

Tiger

Ok Larry, me again, that give you something to think about. I am of the belief that over stabilization is a myth for jacketed bullets. I am just not seeing it myself and what friends are shooting. I think like you and others mentioned cast bullets are not perfect. This and getting damaged getting into the bore is much amplified by faster twists. I would think then that there rpm threshold for bullets that are anything but perfect. But I would not say that fast twists cause inaccuracy.

I don't think it is a myth. The reason is I have been measuring the BCs (the BC is the indicator of a bullets efficiency in moving through the air) of several different weight bullets in not only the 10, 11, 12 and 14" twists of .30 caliber but also several different weights of bullets in 7, 8, 9, 12 and 14" twists in .223. What I am finding is that certain weights of bullets in each caliber will give a higher BC in one of the twists. In other words certain weights of bullets do better in certain twists. For example; in .30 cal the 155 Palma and M80 bullets give the highest BCs in the 14" twist. The Sierra 175 gr MK gives the highest BC in a 12" twist. The 174 gr M118/M72 bullet does the same. The 180 gr MK gives the highest BC in the 11" twist. In .223 the 52 gr match bullets give the highest BC in the 14" twist. The 69 gr MK gives the highest BC in the 9" twist. The 80 gr MK gives it's highest BC in the 8" twist. The difference in BCs between the various twists is quite a bit in some instances. How much? I'll make a comparison of difference is that amound of drop and wind drift between a flat base 165 gr .30 cal bullet vs a 165 SPBT .30 cal bullet at 600 yards given the same muzzle velocity. That is about the difference. So I don't believe "over stabilization to be a "myth", I just don't think it is a constant. Matching the right weight bullet to the twist seems to be what will give the best results.

Larry...think to cast perfect as can cast bullets. Weigh them do all tricks there are before loading. Instead of loading into cartridge case let us push them as perfect straight possible and gentle possible into the bore. Then we load charged case behind it in safe manner you know what I mean. You think this help accuracy?

Tiger, where have you been? I have said over and over again that we can do certain things to push the RPM threshold. Those are several of them and they do help accuracy by reducing the imbalances that the RPM acts upon.

Let me give you something to think about regarding "high angle fire and over stabilization. When we fire a rifle at long range (1000 yards/meters for instance) there is and "angle of departure". A correctly stabilized bullet flies at this "angle of departure" and as it reaches the apogee of its flight it noses over and comes in point first along the flight of it's trajectory. An over stabilized bullet does not nose over and maintains the angle of departure during the last half of it's flight. that means it maintains the same angle as it departed at. The bullet is riding down on its belly so to speak, kind of "belly flopping". The BC is then lowered drastically and accuracy may very well suffer. The bullet slows down quicker, has more drop and more wind drift. This was evident with high power shooters some years back when they shot mexican match and M852 ammo with the Sierra 168 MKs across the course and at 1000 yard matches. They are reputed to go subsonic (they actually do) at 800 meters (900 yard give or take) which is the max effective range as listed in manuals for the M40 and M24 sniper rifles. The twist of the M40 and M24s are 10". Many of us who have shot that ammo with 12" twist M70s or M14s (US NM with 12" twist barrels) know that the bullet stays sonic to 1000 yards (900 meters give or take). The point here is the 168 is slightly over stabilized in a 10" twist and velocity drops off much fast at longer range than the same bullet/load fired out of a 12" twist. That is not hypothetical but fact.

Larry Gibson

[leftiye]

Leftiye obviously just wants to argue. The point in case being his last post; Bass chose to use the 311291 bullets he cast from my mould. L. G.

I would be much gratified if you would stop trying to label me out of the discussion. It's just another form of insult. And again, as usual, somehow you ended up talking about a totally separate subject than the point I made; and then followed that by telling me that, as usual, I was wrong. The comment that I made that you refer to was in reference to 45 2.1's post (not Bass's). I said that it would be nice if you'd permit the use of a boolit that was capable of proving anyone's point but your own. That the 311291 is very poorly designed for velocities higher than 1600 - 1800 fps. And that that is probably why you used it in your tests - because it would perform correctly for what you wanted to prove.

So you see, I didn't insinuate anything. Nor did I advocate letting anybody use Bass's boolit (though it is a much better choice). Who is it that "just wants to argue"? I say it is you. After all it is you that doesn't answer questions, who can't stay on (nor find in the first place) the subject. Etc..

FWIW, I did read Hornady's last page of their accuracy section (yes, I found it without your promised help). And, again, as in the Sierra thing about ballistic coefficients, It was not as you stated. Basically, it only said that bullets wit non-concentric jackets don't shoot as well (yes due to centrifugal force) as better balanced ones do. There was nothing blaming a major portion of inaccuracy on this effect. Especially, there was nothing stating that totally inacurate projectiles could be had due to this type of effect. And lastly, there was certainly no attempt to try to consider all of this to be in a vacuum, and separate from all of the other things that do also cause inaccuracy.

Though Pat I is essentially correct in what he has posted here (and I have been grateful for, and profited from his input), his typifying the negative effects of non-concentric boolit jackets as major ssems to me to apply only in his scenario, that being benchrest. Both with jacketed bulets and cast bullets there are many factors causing more and larger negative effects on accuracy.

It has been most of a year since I stated to Larry that I saw (understood) the effect that he was describing, and agreed that it did in fact exist. Since that ttime, we've wasted our time trying to get Larry to adopt a more balanced, and proportionately closer to reality perspective.

[leftiye]

An over stabilized bullet does not nose over and maintains the angle of departure during the last half of it's flight. L. G.

This is not what is meant by overstabilized in most places where it is used. Nor is it what is meant by "overspinning." Nor is it what Tiger was covering in his posts here.

Firstly, what you describe is only overstabilized in that situation. As long as one is not shooting long range at high launch angles, the bullet flies fine. What Tiger first referred to was that extreme rotational rates seem to have quite small effects upon accuracy. The reference to long range was to say that that is perhaps the only situation where these high rates of revolving have a major or obvious negative effect.

[Pat I.]

Though Pat I is essentially correct in what he has posted here (and I have been grateful for, and profited from his input), his typifying the negative effects of non-concentric boolit jackets as major ssems to me to apply only in his scenario, that being benchrest. Both with jacketed bulets and cast bullets there are many factors causing more and larger negative effects on accuracy

Leftiye, I think you took my comments about concentricity out of context. I never said or meant to imply that it was a major cause of inaccuracy but in the subject we're discussing it's an important and true factor that has to be considered to understand what's being talked about. Also don't think that the same internal and external ballistic laws that apply to shooting a box stock production rifle don't apply to benchrest guns. The point I was trying to make is that it's a proven fact that the more concentric you make a projetile the better it'll shoot for the simple reason that once the bullet leaves the barrel and begins to spin around it's center of gravity instead of it's center of form it doesn't disperse as much on the target.

I really don't expect to get an argument suggesting that with cast bullets we could hope to get anything near the concentricity that's being gotten with jacketed bullets so the question of rpm is a real issue.

A couple of bad comparisons I could make is 1: to put an object on a turn table and run the thing on 33 rpm. The object, if not a feather, will sit there and enjoy the ride. Now turn the rpm up to 78 and there's a good chance whatever used to be sitting there will be long gone. The other example is to off load one pair of jeans in a washing machine and watch how the tub moves during the spin cycle. The faster the tub spins the wider the spiral it makes. Maybe bad examples but I think you get my drift. Anyway if you consider the jeans or object inclusions or air pockets in our bullets, anything that'll make them nonconcentric, that's what's going to happen and the faster they spin the worse it'll get. I think you'd agree there's no such thing as a perfect cast bullet no matter how meticulous we are about casting and inspecting so anything that applies to jacketed applies ten fold or more for cast in this area of discussion.

[Larry Gibson]

Pat I

Obviously from leftiye's posts all he wants is to contradict and argue. Now he is arguing with you. I'm not wasting anymore time on him.

Larry Gibson

[leftiye]

I never said or meant to imply that it was a major cause of inaccuracy but in the subject we're discussing it's an important and true factor that has to be considered to understand what's being talked about. Pat I

Pat,

I totally agree. I think that I and many others do understand this (in spite of larry's assertions to the contrary). It is not a situation where as Larry would like to believe, we're all morons who don't/can't understand his lofty concepts. As I said, the effect of rpms is only one of many factors causing, or influencing loss of accuracy. All that I am advocating is getting this thing into perspective. And that means I will probly not ever worship at the altar of RPMs. I am sorry if my statement rubbed you wrong for some reason.

[Pat I.]

I wasn't rubbed wrong at all but it just seems that of the two camps one, the pro twist limited side, agree it's only one variable that can lead to not achieving best accuracy when there's all kinds of evidence to basically prove it does in both cast and jacketed bullet shooting. While on the other side it's passed off as nonsense and the pro twist limited sides inability to cast perfect bullets, understand how to launch the perfect bullet in perfect allingment with the bore so that damage is minimal or nonexistant, and not using the methodology to make it happen. Larry's suggestion of a test done by starting at 1750 fps and working up in 50 fps intervals using any equipment, loading supplies, and techniques and then honestly reporting back the results is a good one and easily accomplished but I didn't see any takers.

You'll notice that when anyone besides the usual suspects gets brave enough to step into this arena they almost to the man say they get best accuracy at or below the rpm limit Larry suggests but they're usually ignored. I hate to bring up the CBA match program because some people don't like it and others think it's totally different than what's usually done and has it's own set of rules, which it isn't and doesn't, but if you'd take a little bit of time to read the match results which lists the equipment used you'd see people are achieving the accuracy they're getting by following the twist limit idea almost to the key. I'm positive that they don't even think about twist limits when they're building or buying their rifles but just find out by testing that ending up under this limit is where they find best accuracy as I'm sure would happen the same way here.

As both Larry and I have pointed out numerous times we don't say you can't get usable accuracy by shooting faster but you'll get better accuracy by shooting within the limits and as far as I can tell that's what most people want. I don't think it'd be any big trick to shoot 2 or three inch groups at 100 yards at 2400 fps with a 10 twist (maybe) if you wanted to let the barrel cool down between shots and run a rod through every three shots but why would I when I can get better accuracy at 1700 shoot to my hearts content and leave the rod at home.

As far as your assertion that Larry thinks you're all morons I think if your going to point that finger you better raise another so you can hit more than one target.

[Bass Ackward]

Bass, And I guess you'd be entitled to that opinion once you started showing up and beating everybody [smilie=1:. Do you even know what the cast bullet BR crowd is using or the results they're getting? Go take a look at the website sometime and look at the match reports and national records. They're pretty amazing especially considering that they're timed events and you don't get to pick the weather conditions you want to shoot in.




Pat,

I am going to answer both of your posts here.

When I was young, the manly thing to do was to build a street rod that could turn in the 11s between stop lights. I did not choose to beat my equipment in this fashion. I think that it is a mistake to believe that someone who does not have that interest or finances to compete at the benchrest level can not possibly contribute to a discussion. The flip side of that can also be true. And a guy that might have superior equipment and load can't dope wind and he loses.

I never said that the focus of the benchrest crowd wasn't resulting in excellent accuracy. Much of that results from the shooters abilities at handling wind. There is a difference. Because the argument is extreme accuracy, and the throat life is so short in numbers of rounds driven by the way the matches are conducted, accuracy is pursued where the individuals best statistical chance of success makes it easiest to achieve. You could wear out a competition rifle searching for the right load.

If we put in a rule that said that all competitors must use loads that produce 2500 fps or more to be eligible to win, then equipment, cartridges, and techniques would be developed that altered the focus on cast bullet velocity levels. What I found is that the knowledge I learned from this level of shooting improved my lower level work as well. That is the other reason that I do this work and discussion with Larry. At least that has been my results.

I am saying that external factors in air such as wind humidity, altitude affect bullet flight and velocity is a big factor to that. If a good launch is achieved and point forward flight established, it affects fast objects less than slow. Shooting a 220 Swift at 100 yards outside will require less adjustment or compensation than a 22LR in the same wind. The 200 Swift will "appear" to be less RPMy than the 22LR. Somewhere between those two points is the limit of lead governed by jacketed equipment.

Equipment for a long time now has been built for jacketed bullets from which we must operate. This results in accuracy points within those limitations. If you look at muzzle loaders that must deal with fouling, you get the RPM effect at lower velocity levels the more you shoot. If rifling heights were taller, and kept thin so the forward progress of the slug weren't magnified at ignition with a slow gentle lead angle like is cut now with the throat strategies accepted today, then the RPM zone would be established farther up the scale.

Shilen has a cast bullet department that will button you taller rifling if you want it. At least they told me that they did 8-10 years ago. I would suppose that Green Mountain has that capability as well, but I have never contacted them to ask. Any cut rifling manufacturer can cut taller rifling within the constraints of his set-up. And then you can cheat sometimes. But there is a legal impediment. Taller rifling for cast is going to throw more pressure for jacketed so a manufacturer won't build one for just anybody. And then what happens to the rifle upon resale? Please note that I am not saying that taller rifling will be more accurate. Only at higher velocities because it will result in a better balanced bullet and a better launch.

[Bass Ackward]

Folks here seem to misunderstand positions because this argument focuses solely on RPM and they have gone on for so long. Many positions have been altered or eliminated because of them.

Am I saying that twist rate or RPM can not disturb flight? Hell no. That has been proven years ago. It was learned that with a right hand twist, that wind coming from the right would cause a bullet to rise and coming from the left of flight would cause it to drop. A left hand twist is just the opposite. The angle of the propeller effect makes it react more to wind as well. So a faster twist even in the ideal velocity zone is going to have more negative effect than a slow twist rate would for say a 45 caliber. And we all understand how wind causes deflection.

Does any of this have anything at all to do with outta balance? Zippedy do dah. Then, is RPM the reason that we don't shoot one hole?

Where is the line drawn between the RPM effects of air vs. RPM effects of an outta balance slug separate? If you increase either the RPMs, the wind speed, or the propeller angle you get more deflection unless you have more forward momentum which is why 45s shoot better in wind than 22s. IF outta balance was the main factor, the 45 caliber should have more leverage with a longer radius from rotational center and be the less accurate. Do 45s destabilize eventually? Yes. Is outta balance a factor? You betcha. But not at 100 yards.

The three biggest factors that distorts this discussion is the definition of accuracy, range required, and the shooting style of individuals. A fella that is in search of one hole is different from a guy wanting MOA hunting knockdown power at 200 yards with cast. A guy who wants accuracy from a full automatic has to do things different from what a single shot guy might achieve. And the single shot guy is going to stand a chance to have a higher velocity threshold than the full automatic guy. The guy who wants ten shot groups or ten shots in a certain time falls in between there. Does any of that have anything to do with RPM? Does this add to the RPM theory? Yes. Incorrectly, but yes.

If you don't understand what you are observing, you can spend your entire day trying to mold better bullets to beat this effect when you are fighting the wrong battle. The purpose of this board is to advance education even if it's my own.

[45 2.1]

Larry Gibson;426033 45 2.1

"The issue here is accuracy with boolits"

No it isn't. The issue here is the best accuracy with cast bullets in rifles. It is what you fail to understand. I don't think you have any idea what best accuracy is, investigate the current CBA records for an idea. I really think you should get a life, Larry. Nobody is living or shooting by your rules. No one appointed you leader, except maybe yourself. Many of us shoot cast bullets accurately "slow and fast". I haven't seen proof from you of the upper limit yet, just what everybody else can do. 357 Max, BABore and I have shown what can be achieved, by posting groups of the same, when you do things right. The point is the best accuracy will be under the RPM threshold for that bullet/load. For your present level of expertise anyway. Hopefully you can progress past that point. Why don't you run the simple test I suggested Bass run. Shouldn't be difficult for a reloader of your self stated ability. Pick an accurate .308W or 30-06 with a 10" twist barrel. Load some 311291s in 5 shot strings from 1700 up through 2500 fps in 50 fps increments and shoot each group over a chronograph so we'll actually know the velocity. You pick the powder, you pick the lube, you pick the primers, you pick the GCs, you pick the bullet size, weight the bullets if you want, neck size the cases or load them anyway you want. Just shoot the groups 50 fps (+/_ a few fps) apart from 1700 up through 2500 fps. Then let's compare the accuracy of all the test strings and compute the RPM. So show us what you can do. I ran about every concievable test like this back in the late 80's and early 90's. The cost of doing that was quite large, even at that time. Your limited testing does not begin to encompass what factors have a play in getting outstanding accuracy. I'm not doing it again to waste components when I already know how to get what I want.

Larry Gibson

[Pat I.]

Bass

First off throat life on a cast bullet gun is no where near as short as you think. Larry Rickertsen won the nationals a couple of times using a rifle that I'm sure had over 6000 rounds in it. I checked it with my bore scope at what he said was 5000 rounds and it still looked pretty good. There was some wear and cracking in the area but obviously it didn't make much of a difference. There's plenty of guys that have been shooting the same barrel for years and still win matches. There's even those shooting 30 BR jacketed loads that say the throats are lasting 6 or 7 thousand rounds.

If the quest for extreme accuracy is what the cast bullet match program's are all about then shouldn't people look to see what they're doing to achieve it? There's a few of us that do shoot high velocity loads, 26 and 2700 fps, and of the ones that do the common denominator is a slow for caliber twist. 14s for a 22 and 6mm and 17 and 18 for the 30s. Besides the twist and oven heat treating the bullets everything else was done the same as I always have. I had no idea Shilen or GM would build cast specific barrels and when I visited Shilen a few years for a tour they never mentioned it even though I told them I was on my way to a cast bullet match. The downside I see to adding more height to the rifling is introducing more damage to the bullet. Anything you do to a bullet after you pull the trigger is taking away from it's ability so why add more.

We agree on wind drift and such but your analogy of comparing a 22 and a 22/250 might not be the best. You can't compare apples and oranges and no one would say that because a 22 is going to drift more and produce larger groups that it's because of rpm. What I am saying is that if you took the 22/250, lets stick with 30 calibers because I have no experience shooting 22s with cast, and push it past a certain limit the groups will start to open. It might not be catastrophic but they will start to open. The muzzle loader or BPC's aren't good examples either because fouling is fouling and has nothing to do with rpm. But I'd be willing to bet that if they kept the barel squeaky clean and worked up the velocity chart without getting leading their groups would open just like I'm suggesting now.

I still think you should do your experiment with cutting off a barrel if you have one sitting around. Cutting off and crowning a barrel doesn't cost much or take much time and you might gain some insight. I don't think you should use a prescribed load or bullet but use the bullet you think has the most chance of success and work up a load that'll give you the best accuracy. There's a million variables in doing it that could slant the results, including operator bias, but it might prove interesting. I'll be honest and admit that if the higher velocity load shot better I still wouldn't be convinced that cast bullets aren't twist limited because of the variables and my own and other's experiences but it'd give you more ammo for your side of the argument.

Sometimes I get lost in what's being discussed and find it strange that a person will agree with what you're saying while at the same time arguing against it and the only thing that I can come up with to explain it is that in the heat of battle people think that the pro twist limit argument is saying that it's the major cause of inaccuracy when as far as I can tell our argument is that it's a part of it, no matter how small, and easily gotten around by staying in the loop.

[Pat I.]

Larry Gibson;426033 45 2.1

[B]I don't think you have any idea what best accuracy is, investigate the current CBA records for an idea.

And while you're at it look at the equipment lists and calculate the rpm of the guys that shot those records.

P.S. I don't think this was a very good idea to suggest this for your side of the argument.

[45 2.1]

And while you're at it look at the equipment lists and calculate the rpm of the guys that shot those records.

P.S. I don't think this was a very good idea to suggest this for your side of the argument.

Funny, but no where did I state that this was the absolute best accuracy obtainable, because it isn't. I just said he would have an "idea" of it. Just because you compete doesn't mean your the best that there is or the best that can be done. That only applies in the group your keeping records of. Innovations appear thru the efforts of solitary individuals, not a group collective. Not everyone has the urge to compete.

[Pat I.]

I never meant to be funny but it was you that suggested that Larry look at the records and I just added that while doing so look at the rest.

I also never said that I was the best or the match shooters were the best but you do have to admit that they're the best out there at the present time getting verifiable ad repeatable results.

I'm going to have to think about your last sentence about collective vs individuals being responsible for innovation. Personally I've never come up with a truelly innovative idea because I always took from what was already known and worked from there but to suggest that the match shooters aren't individuals and sit around in some star chamber coming up with recipes is a little far fetched.

[45 2.1]

I never meant to be funny but it was you that suggested that Larry look at the records and I just added that while doing so look at the rest. I never meant that you were funny. Different viewpoints could be thought of that way though.

I also never said that I was the best or the match shooters were the best but you do have to admit that they're the best out there at the present time getting verifiable ad repeatable results. When you set a new record, one target for smallest individual group or a series of groups??????????

I'm going to have to think about your last sentence about collective vs individuals being responsible for innovation. Personally I've never come up with a truelly innovative idea We learn from building on previous knowledge usually, don't we. Take for example, the required thickness variation of a jacketed bullet jacket for it to produce match winning results (something in the order of the small ten thousandths). Might that not tell us we need to fit a homogenous (thats another subject all together and weighs heavily on great results) alloyed cast boolit at much closer tolerences to get outstanding accuracy? Have you went that far yet? because I always took from what was already known and worked from there but to suggest that the match shooters aren't individuals I didn't and sit around in some star chamber around the fire at the end of a match or some bull session? It's the directions you don't take that can lead to insights toward progress at times. coming up with recipes is a little far fetched

I'm not interested in arguing with you, but would like everyone to see some progress made (instead of saying you can only do as good as I have) toward the whole of this group in getting much better results than many believe is possible.

[leftiye]

Well, Pat it seems you've lost it. I have just enough problem with your writing that I'm not sure what you're saying, but clouding the issue of what amount of responsibility for causing inaccuracy a given variable occupies in the real scheme of things with the issue of best accuracy is a mistake. ANY VARIABLE THAT DOES ANYTHING DETRIMENTAL TO ACCURACY ACCOMPLISHES WHAT YOU'VE DESCRIBED! i.e. DESTROYS "BEST ACCURACY." Everybody I guess should at this point take up bench rest shooting, because everywhere else (and esecially with cast boolits) there's another scenario. What turns a benchrest load into garbage in most cases is very good practical accuracy. Case in point, if I have a 1" group at 25 yards with a gun, you're not safe to over 400 yards from a hit in the vitals from a correctly aimed shot with that level of accuracy.

I, and almost everybody else have no problem with the idea that best accuracy probly happens at the lowest velocity that you can stomach and with the slowest twist that will stabilize the boolit. The bad news is that at three times that velocity you probly won't have a useless accuracy level, actually maybe almost or even just as good. While we're at it don't forget that air resistance increases exponentially as velocity increases too. Rpms may (I don't think so) be able to explain all inaccuracy, but my experience is that explaining something doesn't mean that you've found the true cause (only that you have an imagination). My quest is to understand the various and relative issues that impair accuracy. And yes, there are reasons that someone would choose velocity over accuracy. For some, the reason is just to see if they can get good accuracy at 3000 fps.


As both Larry and I have pointed out numerous times we don't say you can't get usable accuracy by shooting faster but you'll get better accuracy by shooting within the limits and as far as I can tell that's what most people want Pat I
As I said, I agree with this, just not necessarily for the same reasons that you are advocating. As I said, I understand the concept that you and Larry want to base your salvation on. As I also said there are other factors that are as powerful, or more powerful.

[Larry Gibson]

Bass

Let me take the wind from your sails (pun intended:-) ) Your whole discussion is pertinant regarding the effect of wind on bullets, cast or jacketed. However it has nothing to do with the RPM threshold. In you own examples of faster bullets are dflect less is all the proof. Rememebr the test you ask me to do? The one where you said it would prove this issue? the one you recanted on? the test and it's results you now conveneiently ignore?

The test was simple. (I'm going to talk shooting cast bullets here not building hotrods) It was to take the 311291 (all cast from the same pot, weighed to within close tolerances, etc.) load it at within the RPM threshold and well above the the RPM threshold; in this case 1850 fps and 2500 fps respectfully. The two different loads would be shot for group (10 shot groups, not your usual 3-5) out of my 10" twist .308W at 50 yards, 100 yards and 200 yards. If the dispersion of group size, as the range increased, was linear with both loads then the RPM threshold was false. However, if the linear dispersion was noticeably greater as the range increased with the 2500 fps load and not the 1850 fps load then the RPM threshold was real and valid.

YOU came up with that test Bass. YOU said it would answer the question. I agreed with you and ran the test.

The test results giving the group size (remember these are 10 shot groups) at each range;

50 yards; 1850 fps - .7", 2500 fps - 2.55"
100 yards; 1850 fps - 1.3", 2500 fps - 4.7"
200 yards; 1850 fps - 4.25", 2500 fps 14.5"

Bass, there was little to no wind during the test when any of the groups were shot. Besides, don't you think I would have notice the wind required to blow that bullet at 2500 fps off that much? You were absolutely right Bass, that was an excellent test and it did indeed prove the RPM threshold was valid and existed. However, you did not like the results so you recanted.

Bass, I and everyone else here are well aware of the effects of wind. The inaccuracy caused by RPM on imbalanced bullets is what we are talking about, not the effects of wind on the bullet. Time and again when clear, concise evidence points to the RPM threshold as valid you switch to some other reason that must be the real reason. What's your next try because we all know that wind (and building hotrods) have nothing to do with it.

For 45 2.1s edification the 1850 fps load is not the most accurate load with that bullet in the rifle used. It was the load that fit the velocity suggested by Bass for the test.

Larry Gibson

Adding; Bass, I completely agree with Pat I. As I said in my original response to your proposed test that you should run it I agree that you should and that you should use whatever bullets and loads you deem fit for the test.

[Pat I.]

Maybe I have lost it and ramble on incoherently, who knows, but I reread my posts a few times before sending them along and they make sense to me so if something doesn't make sense let me know.

I think a lot of your post explains why this thing goes on and on. Neither myself or Larry ever said you can't get usable accuracy at higher velocity in fact we both have numerous times. If you're looking for a hunting load that goes 2300 fps and know it'll be good enough for getting into the vitals of a deer at 300 yds go for it. The point is that I was under the impression that we were talking about getting the best, there's that word again and only relates to how rpm effects it, accuracy out of a barrel and not usable for it's intended purpose accuracy. Of course there's a billion variables that will make or break a load but what we're talking about here is solely the what's and whys of rpm, or at least I thought it was and have tried to keep my eyes on that prize.

[Larry Gibson]

Pat I

Well there it is, the experts here have spoken; "Well, Pat it seems you've lost it."

Seems you and I are seeking "salvation" here. I wasn't aware of that. I thought we were discussing "verifiable" and "repeatable" facts. I understood everything you posted as I'm sure everyone except the obvious ones here understood exactly what you said. Same thing with all the PMs I get, they all understand. I have checked the record of the .30 cals used in competion and computed the RPM. They all are within or below the RPM threshold. The 2800 fps load out of the 18" twist has only 112,000 RPM. The couple here who continue to argue do so only because they don't understand or simple just want to argue.

Good posts and I appreciated them as I'm sure many others who been following appreciate them.

Larry Gibson

[Pat I.]

[QUOTE=45 2.1;426784]When you set a new record, one target for smallest individual group or a series of groups??????????

Instead of me having to type a bunch of words explain this to you why don't you take the time to go over to the CBA site and look for yourself. Although I don't know why you'd suggest Larry do it when you haven't seemed to do it yourself.

Since it was me that mentioned jacket thickness and it's effect on accuracy in the first place I guess that just proves you don't read my posts. Casting a perfectly homogenous bullet is a pipe dream and since I run .001 neck clearance, .0003 throat clearance, with a (usually) LBT style bullet weighed to +- a tenth grain tapered in die cut with the same reamer the barrel was throated with yes I have gone that far and beyond.

I've competed with the before mentioned wildcat based on the 35 Rem., a 1.385 long 250 gr 30 cal bullet in a ppc case, a 1.250 long 170 gr 6.5 in a ppc case, and presently with a 30x47 using a 155 gr LBT design at 2600 fps so believe me I've gone in different directions.

[leftiye]

Pat, I understand your desire for the best accuracy. I hope that you can understand my desire for the best understanding of the factors affecting accuracy in a more universal sense. Granted, all of these factors lead up to ultimate accuracy. But perhaps ultimate accuracy isn't the criteria nor arena for determining which factors work which way, and in what situations, and to what relative degree.

I am 100% sure that you are right about why this goes on and on. Pretty much veryone here has agreed on everything (except Larry, he doesn't agree to anything), and it would be so much better to work together on the field than to have to waste our time hearing continually how this or that thing that happened to someone demonstrates RPM when all can see that that is only one of the possible/probable explanations.

But while we're at it, there is a question I want to introduce concerning rpm effects. I suppose you've heard of tests having been done to determine the relative effects of boolit nose deformation versus base deformation. Now rpm "theory" says that either would be equally detrimental. In fact, drilling a hole in the side of the nose or base of a boolit should (my guess) give Centrifugal force just what is needed to throw the boolit into next county. However, the legend has it that uneven base deformation has much greater effect (even when a hole is not drilled in the base). If you go with air resistance as being the cause, the yawing caused by the uneven base causes more deflection than the uneven resistance that the hole in the nose produces.

Another example. A boolit that is slightly out of balance is fired (we'll assume that all else is optimal). Rpms then gets hold of that there poor boolit and makes it yaw (notice that it is still on the original flight path). Air resistance takes over and makes it fly in a spiral due to the yawing. Do we now say that this demonstrates rpms or air resistance? The correct answer is neither, it was the unbalanced boolit that caused it. The centrifugal force, and the deflection were just thangs that the boolit had to weather en route to the target. Which effect ws greatest? My money is on air resistance.

Something else to ponder. In the vacuum in which the proponent(s) of RPM theory like to present the example ot the unusual boolit (you've gotta admit that this is only probable with jacketed bullets having faulty jackets) that is equally out of balance along its length, and therefore oscillates parallel to it's axis of weight or form (whichever way you choose to see it), what does it take for that boolit tototally lose it and fly off to parts unknown? Does it get progressively worse to an infinite degree?, or does it only progress to a moderate amount of oscillation and then exit the box all at once? Remember that the drilled boolits still printed groups when rpms would predict them to go south. Thatsa sum imbalance, BTW!

[Pat I.]

Good questions and the only answers I'm going to be able to give will be theoretical and my opinion.


"But while we're at it, there is a question I want to introduce concerning rpm effects. I suppose you've heard of tests having been done to determine the relative effects of boolit nose deformation versus base deformation. Now rpm "theory" says that either would be equally detrimental. In fact, drilling a hole in the side of the nose or base of a boolit should (my guess) give Centrifugal force just what is needed to throw the boolit into next county. However, the legend has it that uneven base deformation has much greater effect (even when a hole is not drilled in the base). If you go with air resistance as being the cause, the yawing caused by the uneven base causes more deflection than the uneven resistance that the hole in the nose produces"

I've seen these tests but what I haven't seen is a way to get perfectly identical samples and remove the exact same amount of material from the exact same center line of the bullet nor have I seen any testing on how rpm would effect it . It does stand to reason that the steering end of the bullet will have a much bigger effect than the nose but in the subject at hand I don't see how this question applies to what we're talking about but I could be wrong. Either way a bullet without a hole drilled in the bottom or nose is going to shoot better than one that does and might lead to more proof that rpms have an effect.

"Another example. A boolit that is slightly out of balance is fired (we'll assume that all else is optimal). Rpms then gets hold of that there poor boolit and makes it yaw (notice that it is still on the original flight path). Air resistance takes over and makes it fly in a spiral due to the yawing. Do we now say that this demonstrates rpms or air resistance? The correct answer is neither, it was the unbalanced boolit that caused it. The centrifugal force, and the deflection were just thangs that the boolit had to weather en route to the target. Which effect ws greatest? My money is on air resistance."

Air resistance isn't going to make a bullet spiral, not being concentric to the center line is. Air will slow a bullet down or push it off course but it's dispersion that we're talking about here and what effects rpm has on it. Deflection and dispersion are two totally diferent things.

"Something else to ponder. In the vacuum in which the proponent(s) of RPM theory like to present the example ot the unusual boolit (you've gotta admit that this is only probable with jacketed bullets having faulty jackets) that is equally out of balance along its length, and therefore oscillates parallel to it's axis of weight or form (whichever way you choose to see it), what does it take for that boolit tototally lose it and fly off to parts unknown? Does it get progressively worse to an infinite degree?, or does it only progress to a moderate amount of oscillation and then exit the box all at once? Remember that the drilled boolits still printed groups when rpms would predict them to go south. Thatsa sum imbalance"

Actually the bullets having a known concentricity fault would be easier to work with if you could find a way to index them. With our cast bullets the problem could be anywhere throughout the bullet and no matter what you do short of destructive testing you couldn't find them. I don't think the bullet ever exits the box all at once unless you get to the point where it loses stability but do think it'll shoot like a funnel where the farther away it gets the more the spiral will increase in size.

I don't know if my opinions meant anything or if my answers were comprehensible. In fact I don't even know if I was answering what you asked but it's the best I could do.

[Larry Gibson]

I am amazed! I started this whole RPM threshold thing on this forum. I defined it by stating waht it was and what it wasn't. I also set out to test the validity of the RPM threshold. I did that in every instance which included a few tests suggested by the detractors. It has always been about the evel of velocity with a certain twist where accuracy goes south. It has always been agout where best accuracy is found". Now two of the detractors want to rewrite the definition so it fits their untested concepts.

Well excuse me but that is akin to (I'll reference hot rods here) saying after you lost the 1/4 mile drag race that it didn't matter who crossed the finish line. What mattered was who crossed the 1/8th mile first because it was you! Or how about at the end of the of the football game (2 minute warning) when you are down by 30 points you rewrite the rules so the team with the least points wins! Sorry guys but it doesn't work that way. The RPM Threshold is well defined. It is about the best accuracy and where that best accuracy is obtainable.

If someone wants to change this discussion to a "useable accuracy" discussion and where that can be found then that's fine. Simply define "useable accuracy", start a thread and let's discuss. But keep in mind that a discussion of the RPM threshold centers around "best accuracy" and where that is found, not "useable accuracy" where ever and what ever that may be or found according to whatever the definition is going to be.

Larry Gibson

[Larry Gibson]

Pat I

I conducted such a test and it was included in Chaper I which was posted on this forum. The reason for this test was because of the objections on the validity of the tests I was about to conduct. The detractors began to detract even before the testing as the RPM threshold goes against the preconcieved notions. They are sticking to those notions regardless of any actual test proof to the contrary. They only desire an arguement. I post this for you information.

Here is the part from Chapter I;

To demonstrate the validity of these test methods a simple test was conducted with the 10” twist rifle. The M43 was set up with testing done at 100 yards. M118 Special Ball was used for the test. Now I think we can agree the 174 gr M118 bullet is not going to suffer any set back, bending, torque twisting or undue obturation during acceleration. At any rate, the test here is between regular M118 bullets and those I purposely unbalanced. If the regular M118 bullet suffers any of the mentioned deformations then the unbalanced M118 bullets would suffer the same deformations. So what we are testing is what the different effect of RPM will be on the balanced and unbalanced bullets.

This lot of M118 ammo, while 1.1 – 1.2 moa accurate in 12” and 14” twist barrels has not been much better than 2 moa in 10” twist barrels including M24 sniper rifles. And so it was with the M1909 with 10” twist. A ten shot string of regular M118 bullets was fired and they grouped right at 2 MOA. Then the ten shot string was then fired with the same lot (actually with the other 10 rounds out of the same 20 round box) of M118 that I had drilled a hole in the side to unbalance the bullet. I used a #31 drill and drilled the hole .06” deep removing 1.7 gr of the bullet in the side right in front of the case mouth. The M43 showed that the unbalanced bullets, when compared to the regular M118, averaged 5 fps faster MV, had a slower TOF, down range velocity was slower and had a lower BC. This is ample evidence the unbalanced bullets were not as stable in flight as the regular M118. The clincher was the group. The regular M118 grouped 2 MOA and the unbalanced M118 grouped into 6 MOA. Ample evidence of how the centrifugal force of the RPM affects the accuracy of unbalanced bullets.

Note that the holes were drilled using a drill press with an adjustable mill table/vise. The bullets where ridgedly held and the holes were drilled to the same depth in the same place on each bullet. The results speak for themselves. Leftiye, 45 2.1 and Bass continue to conveniently forget any actual test that proves them wrong and the RPM threshold valid. This is only one such test that they continue to forget.

Larry Gibson

[45 2.1]

Deliberatly sabotaged ammo usually does that. I can do the same thing with a hammer also. So really Larry, what was the purpose of this. A never ending arguement so you can write long winded statements and say you can't do this? Exactly who has that helped? This issue will never have an end as long as your on that soapbox. I don't care if you believe it or not, but I don't want you poluting those who don't know enough to realize what your trying to say has many other reasons why it occurs. And no, I don't believe it was an effort by you to tell someone why they can't get good accuracy past a certain point. And BTW, the best accuracy can occur where you least expect it, around 600 to 700 fps in rifles. Some of the CBA members finally found that out a few years ago. Not much fun shooting those loads in the wind though.

[Pat I.]

And BTW, the best accuracy can occur where you least expect it, around 600 to 700 fps in rifles. Some of the CBA members finally found that out a few years ago. Not much fun shooting those loads in the wind though.

I'm really getting kind of pooped from all this but would you mind providing reference where this came from? I have access to all the old Fouling Shots and know a lot of the match shooters personally so wouldn't have a problem tracking it down.

Seems to me that unless you're talking about one of the pistol calibers or had the target two feet from the muzzle you'd have to run a pretty pint sized bullet to have a rifle stabilize it out to 100 yds with a muzzle velocity of 6 or 700 fps.

[45 2.1]

I'm really getting kind of pooped from all this but would you mind providing reference where this came from? I have access to all the old Fouling Shots and know a lot of the match shooters personally so wouldn't have a problem tracking it down.

Seems to me that unless you're talking about one of the pistol calibers or had the target two feet from the muzzle you'd have to run a pretty pint sized bullet to have a rifle stabilize it out to 100 yds with a muzzle velocity of 6 or 700 fps.

A couple of members were running loads out of a 30 BR as I recall. I only remember one article on it also. I'm not sure, but I don't remember what there velocity was, but it was quite low for the set-up. Those were my velocities, not theirs and I did it with a 38-55 and a 45-70 (a lot of times, so it wasn't a fluke, just a trick load thats worthless except for shooting bugholes).

[leftiye]

Air resistance isn't going to make a bullet spiral, not being concentric to the center line is. Air will slow a bullet down or push it off course but it's dispersion that we're talking about here and what effects rpm has on it. Deflection and dispersion are two totally diferent things. Pat I

Oh yeah it does! Remember that as the boolit or bullet "footballs" that the nose describes a spiral and that the resultant deflection follows suit - ie. it literally steers the boolit in a spiral as it rotates. FWIW, this is exactly what makes a boolit started with a yawing problem by a poor launch fly in a spiral. Also FWIW your "dispersion" is actually deflection. The boolit is deflected from its original path. Does the source of deflection make it other than deflection?

[Pat I.]

OK you win and I give up.

[Larry Gibson]

OK you win and I give up.

Pat

I give up on these 2 also. They will not listen to anything. Leftiye is really "out there" with his concepts which are not backed up by anything. As to 45 2.1 not letting me "poluting those who don't know enough to realize what your trying to say" he obviously doesn't realise that many do listen to me. They know it's not polution and that he only discredits himself. He makes statements of "facts" to you and then recants when you call him on them because he knows he was just making it up and has nothing to back it up with.

What's so great about accurate loads at 600-700 fps anyway? We all post such loads including myself. I'm sure you and most everyone have read my posts concerning the TL314-90-SWC out of .30/.31 rifles over 2.7-3.2 gr of bullseye. Or the Rapine 460250 over 8 gr of Bullseye in the 45-70...or the "cat's sneeze" load of 2.7 gr Bullseye under the 323471 for 538 fps. The point here is 45 2.1 always brings up such that does not pertain to the issue or discussion. He apparently thinks it gives him credibiltiy. Yet it does just the opposite. I'll break down here and ask 45 2.1 one question' How many 600-700 loads, even in the Swede's fast twist, are even close to the RPM threshold let alone exceed the RPM threshold? The answer is none, nada, zip. Thus your "expert opinion and comment" is not germain to the issue at all. 45 2.1 only brings up such because he likes to argue.

Bass at least is trying to be constructive. He at least is willing to test and even has changed his mind a bit. In the beginning he didn't think RPM had any adverse affect. Now he at believes there is some. Still may be hope for him and I will probably discuss this with him in the future. If he actually does do his test I hope he will post the results on another thread.

I recieved a PM today asking me if I really was recieving PMs from memebrs supporting me and the RPM threshold. Yes I do. The problem is almost all will not post any support because of the haranging and verbal abuse they know they recive from the 3 mentioned. They know the 3 will not listen to reason and will only ridicule them. It is too bad but that is the way it is.

I am with Pat I and through here also.

Larry Gibson

[leftiye]

"Who's zooming who?"

Yawn, Larry that's the problem - they do listen to you (and waste their time). To paraphrase an old disco song - Who's abusing whom?

[45 2.1]

OK you win and I give up.

With all your connections you should find it easily. Come on now, don't be a quitter.


This one is Larry's:
What's so great about accurate loads at 600-700 fps anyway? We all post such loads including myself. I'm sure you and most everyone have read my posts concerning the TL314-90-SWC out of .30/.31 rifles over 2.7-3.2 gr of bullseye. Or the Rapine 460250 over 8 gr of Bullseye in the 45-70...or the "cat's sneeze" load of 2.7 gr Bullseye under the 323471 for 538 fps.

Yah, they might do that, but what do they do at 100 yards? Come on now, tell the good folks here. Were they good enough to shoot CBA competition with and win?

[Bass Ackward]

Bass

1. First off throat life on a cast bullet gun is no where near as short as you think.

2. If the quest for extreme accuracy is what the cast bullet match program's are all about then shouldn't people look to see what they're doing to achieve it? There's a few of us that do shoot high velocity loads, 26 and 2700 fps, and of the ones that do the common denominator is a slow for caliber twist. 14s for a 22 and 6mm and 17 and 18 for the 30s. Besides the twist and oven heat treating the bullets everything else was done the same as I always have.

3. The downside I see to adding more height to the rifling is introducing more damage to the bullet.

4. We agree on wind drift and such but your analogy of comparing a 22 and a 22/250 might not be the best. You can't compare apples and oranges and no one would say that because a 22 is going to drift more and produce larger groups that it's because of rpm.

5. I still think you should do your experiment with cutting off a barrel if you have one sitting around. Cutting off and crowning a barrel doesn't cost much or take much time and you might gain some insight. I don't think you should use a prescribed load or bullet but use the bullet you think has the most chance of success and work up a load that'll give you the best accuracy. There's a million variables in doing it that could slant the results, including operator bias, but it might prove interesting. I'll be honest and admit that if the higher velocity load shot better I still wouldn't be convinced that cast bullets aren't twist limited because of the variables and my own and other's experiences but it'd give you more ammo for your side of the argument.




Pat,

1. I never said what I thought about throat life. I merely stated that because if someone put the money into a quality outfit, they are going to want to baby it for as long as they can. And if you were to take a poll for accuracy, I will bet a short clean throat would rank in the top 3. Why? Because the guys shooting the records all have them. So is throat length another RPM theory or can the law be broken. :grin: (military testing has shown that even with worn throats in barrels with 12,000 rounds, accuracy can be restored by cutting 1/4" off the muzzle and recrowning cause it's all in the launch.) But if you learn that light cast shoot faster / better, then you are going to want a short throat.

2. I never said that slow twist wasn't an aid. In fact I listed that one. But it strengthens lead as I will describe in 4 so that you launch better, not because you generate lower RPMs. The fact is that human nature is that given the choice between two things, the vast majority will always take the easy way. Especially if you give a prize for getting there first of best. People that could contribute to the understanding and therefore improvement took the easy path. Now the argument can be made, we have jacketed for that. But the same argument can be made for accuracy as well. that myth has fallen. Lets get the next one. But people are free to compete anyway they want. The more minds working on something, the sooner and better things would get. That's just statistics. The reason that the RPM zone is where it is is because of where the most shooting is done. Not because of RPM.

3. There is always a peak. Two questions come to mind and one of them is generated by you. A. Have you tried it? B. Don't you damage the bullet when you fire it? So wouldn't there be a balance point there as well? I have one in 45 caliber. It will shoot softer to do the same thing as I did with harder. But that's only one barrel. Will there be more? You betcha. My theory is displaced lead is displaced lead. If you can displace it with wide rifling, why not with tall. Wide contributes nothing to drive area, but tall does. Tall being defined as say up to .007. Same with more lands.

4. Shooting a match is not just about a bullets ability to group but the ability to place the shot. IF you shoot 22s indoors, you are aware of how accurate they can be, but outside no where close. That was the 22 Swift analogy. And a less experienced shooter might not understand because the difference is velocity which also happens to be RPM. So is it velocity or RPM?

This is the key. If you were to take all the benchrest boys and require pure lead, RPM levels would be lower. If you made them use worn micro groove barrels the RPM zones would be lower. Why does harder lead shoot to higher velocity? Why does an equal weight / length jacketed bullet that has a pure lead core that is assembled and outta round that obturates and shortens more easily than a hard cast bullet, shoot higher RPMS than cast? IF you answer bullet grip of the rifling, you understand my point. You must launch well. If you didn't and you are still an RPM believer, then you have to admit that the best accuracy for the jacketed slugs will ALWAYS be at the 1700-1900 RPM zone because it is just as outta balance as the good hard cast. But sometimes Pat, the bullet that deforms and compresses attains more rifling contact and can become stronger than a hard cast one of poor design. (remember the 6.5-06 test) As a result it can launch better and turn out to be more accurate than a hard cast bullet that doesn't. That violates the RPM rule because it is uncontrolled balance. What changed? Your twist rate in the barrel? The RPM monster took a break? Nope, the way the bullet held the rifling and launched. See 1. above.

5. I have done this before but not with cast. Problem is time. My point is that the harmonics can be entirely different and skew the results more than the damage from the load. Taking all the factors that are involved in accurate shooting and combining them into a single ahhh "$hit happens" RPM theory hurts education. Since the zone for all weight and length cast in 30 caliber is in the same zone area, shouldn't we all send a petition to the Armies of the world and tell them to quit wasting our money on accuracy experiments and just load everything down to 1700-1900 fps? Would anyone have the courage to go to a range and tell folks shooting jacketed that accuracy can not be attained above the RPM barrier? Anyone agree to sign / do that? :grin:

[Bret4207]

Aren't you guys getting tired of chewing on each other? Everyone agrees there are possibilties and apparant limits, this works sometimes and other time's it doesn't. All you're accomplishing now is peeing in each others Wheaties. Whats the use? Why not take a break until someone comes up with something new?

[Pat I.]

As for my participation in this I say let's just agree to disagree because I'm starting to feel like I'm in the Twilight Zone.

[Bass Ackward]

As for my participation in this I say let's just agree to disagree because I'm starting to feel like I'm in the Twilight Zone.



I do understand really. Who is hurt by the acceptance of the RPM theory anyway? Same as with the sun theory for centuries. A new sun rose every morning as the old one burnt out the night before. Sure seemed that way and life went on as usual.

Ooops, that was proven to be the RPM theory. :grin:

[Larry Gibson]

Bret

I backed out of this thread several posts back. I can't reason with anyone about cast bullets when they don't even understand the differences between cast bullets and jacketed bullets. Thus I gave up as I've said. So I guess peeing on the wheaties makes you the knowledgeable expert around here and thus we can fail to expand our knowledge. Fine with me but with the number of views this thread and the others got, along with the PMs I'd say there was more interest than just watching the wheaties get pee'd on. None the less I hope Bass does do his test and reports on another thread.

Larry Gibson

[Bret4207]

You're all free to continue as you wish, please understand that. It just seems there's a lot of wheel spinning and snappy ankle biting going on. No skin of my nose if that's how you guys want to spend your time.

The only rule is to avoid personal attacks and insults. Other than that, game on!

[leftiye]

Larry, Maybe while we're at it we could refrain from blaming our problems on what we knowingly distort to be our opponent's lack of comprehension (while at the same time ignoring the issues). Your own lack of coherent arguement got you here. That and your refusal to allow a resolution that included anything outside of your own viewpoint. (IMHO, That's what all this bullstuffing on your part is really about)

[runfiverun]

had to jump back in here, [just can't resist]
but i am thinking that if your boolit is actually large enough around and it is being squeezed enough.
[like the results of bass's 65 test.]
is that not being swaged?? doesn't this remove air trapped in the lead.
if so.. is it not being swaged as a[near] perfect copy of the inside of your bbl?
this is how the taller rifling affects the boolit in a positive way.
and how the depth of your lube grooves affect it's the [boolits] grip on the bbl.
awww crap some insight....and a question????
but will post it in a another thread.

[45 2.1]

awww crap some insight....and a question???? but will post it in a another thread.

I doubt you'll get insight from Larry, but he WILL tell you you can't do anything over about 1600 fps because of RPMs. Thats the problem with the RPM theory, it keeps getting shot full of holes from Larrys common unbalanced boolits.

[Pat I.]

Damn it Bass quit writing because I finally got around to reading your post and have to comment on some of it although very little has to do with RPM. This is it though for sure (until next time).


Pat,

1. I never said what I thought about throat life. I merely stated that because if someone put the money into a quality outfit, they are going to want to baby it for as long as they can. And if you were to take a poll for accuracy, I will bet a short clean throat would rank in the top 3. Why? Because the guys shooting the records all have them. So is throat length another RPM theory or can the law be broken. :grin: (military testing has shown that even with worn throats in barrels with 12,000 rounds, accuracy can be restored by cutting 1/4" off the muzzle and recrowning cause it's all in the launch.) But if you learn that light cast shoot faster / better, then you are going to want a short throat.

These are your words from an earlier post "Because the argument is extreme accuracy, and the throat life is so short in numbers of rounds driven by the way the matches are conducted, accuracy is pursued where the individuals best statistical chance of success makes it easiest to achieve. You could wear out a competition rifle searching for the right load."........ Ok enough about that

It's a supposition on your part that all the record holders have short clean throats and I can tell you for a fact that some don't. I'd also be willing to bet most have a relatively long one and some throats that would be considered real long. As for your statement about the military I'll counter to say that in jacketed bullet BR most competitors won't even set back and refit used barrel because they've found they won't hold their accuracy for very long if it shoots as good in the first place. Of course military standards and jacketed BR standards are two different things but that's the facts.

2. I never said that slow twist wasn't an aid. In fact I listed that one. But it strengthens lead as I will describe in 4 so that you launch better, not because you generate lower RPMs. The fact is that human nature is that given the choice between two things, the vast majority will always take the easy way. Especially if you give a prize for getting there first of best. People that could contribute to the understanding and therefore improvement took the easy path. Now the argument can be made, we have jacketed for that. But the same argument can be made for accuracy as well. that myth has fallen. Lets get the next one. But people are free to compete anyway they want. The more minds working on something, the sooner and better things would get. That's just statistics. The reason that the RPM zone is where it is is because of where the most shooting is done. Not because of RPM.

Believe me your not going to get rich shooting cast bullet BR matches considering most of the time you don't win anything except a hardy handshake. If people were looking for an easy path they sure wouldn't pick bench rest shooting as the one to follow. What I think is that you're putting the cart before the horse here. Most improvements in factory arms, loading techniques, and accuracy over the last 10 or 15 years or so are direct decendents of jacketed and cast BR shooters and what they've learned. It wasn't that many years ago that throats weren't even a topic when discussing cast bullets, the normal discussions at the time were how many thou to size over bore diameter. As for your closing sentences has the thought ever occured to you that the reason people are shooting in the RPM zone is because that's where people are getting the best accuracy? RPM is a long known but seldom discussed topic and I'd be willing to bet that before Larry brought it up here most people never even gave it a second thought. Does it just happen to be a coincidence that most people, BR and everyone else, are finding their best accuracy in the zone and there's the slight possiblity that there's something to it.


3. There is always a peak. Two questions come to mind and one of them is generated by you. A. Have you tried it? B. Don't you damage the bullet when you fire it? So wouldn't there be a balance point there as well? I have one in 45 caliber. It will shoot softer to do the same thing as I did with harder. But that's only one barrel. Will there be more? You betcha. My theory is displaced lead is displaced lead. If you can displace it with wide rifling, why not with tall. Wide contributes nothing to drive area, but tall does. Tall being defined as say up to .007. Same with more lands.

Since we're both just thinking out loud here and have no experience to back up our claims all I can say is go for it and see what happens. I don't know this for a fact but probably you're best bet would be to approach one of the barrel makers who uses cut rifling, Krieger comes to mind since they make excellent barrels.

4. Shooting a match is not just about a bullets ability to group but the ability to place the shot. IF you shoot 22s indoors, you are aware of how accurate they can be, but outside no where close. That was the 22 Swift analogy. And a less experienced shooter might not understand because the difference is velocity which also happens to be RPM. So is it velocity or RPM?

This is the key. If you were to take all the benchrest boys and require pure lead, RPM levels would be lower. If you made them use worn micro groove barrels the RPM zones would be lower. Why does harder lead shoot to higher velocity? Why does an equal weight / length jacketed bullet that has a pure lead core that is assembled and outta round that obturates and shortens more easily than a hard cast bullet, shoot higher RPMS than cast? IF you answer bullet grip of the rifling, you understand my point. You must launch well. If you didn't and you are still an RPM believer, then you have to admit that the best accuracy for the jacketed slugs will ALWAYS be at the 1700-1900 RPM zone because it is just as outta balance as the good hard cast. But sometimes Pat, the bullet that deforms and compresses attains more rifling contact and can become stronger than a hard cast one of poor design. (remember the 6.5-06 test) As a result it can launch better and turn out to be more accurate than a hard cast bullet that doesn't. That violates the RPM rule because it is uncontrolled balance. What changed? Your twist rate in the barrel? The RPM monster took a break? Nope, the way the bullet held the rifling and launched. See 1. above.

If people, match shooters and otherwise, were forced to use pure lead or worn microgroove barrels you'd be forced to shoot slower by design so I don't understand the relationship to what we're discussing. I also don't understand your first paragraph since we're not discussing the effects of wind on a bullet.

In the first place for all we know some of the second jacketed bullets you can buy would shoot better at 1900 fps and secondly you can't possibly believe that a cast bullet is going to be as concentric as a jacketed. My believe on why you can shoot a harder bullet faster is that it doesn't compress and cause enough pressure against the barrel walls to overcome the lubes ability to both lube and prevent melting which would just lead to a more unbalanced bullet.

I don't see how a soft bullet that compresses can have any better grip on the rifling than a bullet a couple thousandths over bore diameter to begin with. Pressure peaks within the first few inches or less of travel and it's a pretty well established fact that you don't want to distort a bullet any more than necessary for best accuracy. What it sounds like to me is that you're placing every thing on the crown and rifling height and if you have a both that's all that matters so we can call yours the "crown high rifling theory" :)..

5. I have done this before but not with cast. Problem is time. My point is that the harmonics can be entirely different and skew the results more than the damage from the load. Taking all the factors that are involved in accurate shooting and combining them into a single ahhh "$hit happens" RPM theory hurts education. Since the zone for all weight and length cast in 30 caliber is in the same zone area, shouldn't we all send a petition to the Armies of the world and tell them to quit wasting our money on accuracy experiments and just load everything down to 1700-1900 fps? Would anyone have the courage to go to a range and tell folks shooting jacketed that accuracy can not be attained above the RPM barrier? Anyone agree to sign / do that? :grin:

I guess I'll have to add the word harmonics to your theory. I've said this over and over til I'm blue in the face but I'll repeat it one more time just for you. Nobody ever said that RPM is the only factor to accurate shooting. All anyone said was that it's A factor that should to be considered no matter how small. I don't understand why that's so hard to get since it's been tested and proven by both cast and jacketed shooter and manufacturers that forgot more than we'll ever know.

How much better than a Heavy Class four five shot group aggregate record shot at 100 yds at just under 2000 fps with an 11 twist barrel that measured .278 do you think you're going to get by shooting fast? Or how about the 100 yd 5 shot agg record shot with a .243 in a Production class gun, a Ruger 77 no less, that measured .422 at 1980 fps in a 10 twist. Don't you think the guys that shot these records and the rest of them tried different things and velocities to improve accuracy and beat the wind?? I'm sure they did but always ended up rght back where the RPM thing says you should be. One more time, rpm isn't the end all of accurate shooting but it's something that has to be considerd

Now I'm really pooped and might have rambled a bit more than I wanted to, sorry. But I will use my crabbiness as an excuse for what I'm about to say....

45 2.1, Do you ever add anything to a conversation besides wisecracks and negative comments???? I never remember seeing anything you've ever posted that wasn't derogatory or had a derogatory comment thrown in for good measure. Claiming to have BTDT and that everyone but you needs to learn how to make it happen is both iritating and childish. Nobody knows everything and maybe if you took a minute or two to actually read what was being written instead of rushing to tell everyone how you've BTDT or how they're methodolgy isn't up to it you just might learn something you don't know, if that's possible

To everyone else I apologize but enough is enough. I don't plan on posting anymore so please don't close down the topic because of this. From the amount of views there seems to be some interest, although sadly I wonder how many look just to see the show.

[leftiye]

R5R, I don't claim to be an expert on what you just asked, but while a lot of swaging is going on in engraving, and etc., I don't think it actually irons out the defects like we might want. In fact, there is the probability, though it is in effect forging the bullet some, that it doesn't really do it uniformly and result in a balanced boolit.

On a related subject (not directed at you - R5R necessarily), I think we all need to examine why a naked boolit is so hard to get to fly fast, when an even softer boolit that is patched makes it to be relative child's play. [Larry got away with excluding patched boolits in his test discussions, but this ain't his thread, and he can't exclude whatever he doesn't want to consider here - as has been his habit everywhere else] For my money, the lead is a very poor metal for the outside of a bullet, plain and simple. Too much goes wrong with naked lead, and all of it affects accuracy in a major way. One of my guesses has been for a long time that the lead acts in a more ductile manner while transversing the barrel than we usually assume it does. Perhaps due to heat. We can't assume that nothing happened along the way because we find a boolit in the berm, and it appears normal. Even if we had a lab minutely examine that boolit, there is no guarantee that the sudden stop didn't change things (it would be much wiser to expect that this DID change things) and the testing was to no avail.

[45 2.1]

45 2.1, Do you ever add anything to a conversation besides wisecracks and negative comments???? Well, I get this way through the antics of fellows who don't take known data and causes into account and from gents who claim they can check things out easily, but beg off for some reason. I can be crabby also, so your not alone. I've followed your and JoeB's antics in the Fouling Shot and the CBA forum from its inception, so I know both of you have your detractors there also. I never remember seeing anything you've ever posted that wasn't derogatory or had a derogatory comment thrown in for good measure. You've not been here long. There is quite a large data base here with a lot of files saying otherwise, provided you cared to look. Claiming to have BTDT and that everyone but you needs to learn how to make it happen is both iritating and childish. Tough, isn't it. Nobody knows everything Maybe you should remember this when you write something yourself, good advice. and maybe if you took a minute or two to actually read what was being written instead of rushing to tell everyone how you've BTDT or how they're sp. methodolgy isn't up to it you just might learn something you don't know, if that's possible There is the other end of that, ie maybe I have done that and taught others how. Can you run a 35 Whelen at over 2600 fps and put a five or six shot group in under 0.7" at 100 yds. Can you put 5 shots from a 450 Marlin in less than 0.5 MOA at 2250 fps. When you can, then you can say the same things we do. Until then though, I wish you would read some back posts.

[sundog]

ya know, I kinda stayed outa this one until now, but I just had a thought. With NO rifling, the boolit is UNDER stabilized. Think about it.

[leftiye]

Flies like somebody's "overstabilized" boolit is said to?

[Larry Gibson]

45 2.1

I wasn't going to post here anymore but your blatant untruths calls for a response.

You stated; "I doubt you'll get insight from Larry, but he WILL tell you you can't do anything over about 1600 fps because of RPMs."

When did I ever say that? The fact is I have said just the opposite. You know it and everyone else does It is now quite obvious to everyone that you've absolutely no idea what you are talking about and simply making untruths up as you go.

You and leftiye should not be so mordent, the forum would be a nicer place and those of us who want to discuss things and even perhaps disagree could do it in a reasonable and *********t manner.

Larry Gibson

[Bret4207]

Okay. That's it. "bullstuffing", "untruths", enough.