Penetration Testing and HIGH RPMs? :grin:

[Bass Ackward]

I was absent from here for about 6 months while I was off doing MANY of my unscientific tests. I felt that I could NOT be distracted by this board which so often happens with others of varying opinions. So .... fortunately and unfortunately for many here, here is one of my tests.

The test began involving 4" and 6.5" 44 S&Ws for hardness requirements, both with throats smaller than bore diameter (that is another thread all to itself) and penetration.

From this testing, I got another wild idea to try. And that is the subject here. RPMS can not be measured. BUT!!! RPMS are not necessary in a vacuum. Only when traveling through some medium, such as air ............... OR animal flesh. Thus, the depth of "accurate" penetration could be thought of as a reflection of "actual RPMS" and only "IF" deformation could be controlled. So how could I see this?

The idea was to use increased resistance to slow penetration without causing ANY deformation. That leaves RPMs as the sole factor for stable, penetration depth. This is too hard to do at high velocity, so lets slow it down and soften the slugs. I used a 30 caliber rifle for this so that it would make it easier for others to understand and correlate it to as we went along.

I mixed up some ballistic gelatin provided by a friend in long plastic (double bread) bags so that I could see inside. I used one milk jug with water in front of the gelatin for each shot to slow the projectile uniformly with the intent to stop it in the gelatin tubes. It took a lot of working out the kinks, but what I eventually did, I used Linotype for the nose portion of a pure lead body bullet utilizing my 160gr, GC, 30 caliber bullet design with a 60% meplat. This was to prevent mushrooming from contaminating the results. All of this was fired from my 30-06 at 50 yards which is unimportant, except it establishes a base line.

Accuracy levels were no real consideration here either. I say that with the understanding other than what the "best" accuracy level was and at what velocity level that occurred. I was using 4759 powder, magnum primers, and Dacron to maintain shot to shot velocity consistency with a chronograph in front of the impact area. What happened during this testing was an epiphonony on RPMs.

Accuracy peaked between 1150 and 1200 fps. It began to deteriorate rapidly above this level where I shot it up to 1600 fps. 1600 fps was the stopping point because accuracy was about 2 1/2" which was the limit for a guaranteed hit in my gelatin tubes. And the nose also began to exhibit signs of deformation which would contaminate these results.

What happened was amazing and a truly key point!!!. Penetration peaked, when accuracy peaked. Now why?

As velocity increased from the 1200 fps level, more violent reaction was noted in the water action at the jug resulting from the increased velocity level strike, but penetration was no deeper at 1500 fps than it was at 1200 fps. And at 1600 fps, penetration actually declined. No mushrooming was present. So was RPMs actually declining as velocity increased? :grin:

At 1400 fps, the penetration was clearly no longer straight line. The slug began to veer off coarse and became RPMy looking as it traveled. At 1600 fps, the penetration was truly erratic and the slug even began to exit the side of the gelatin tube on a few of the shots.

Next I hardened the slug. This time I used Linotype, just to ensure that there was enough of a difference in hardness to prove my theory. The Linotype bullets at 1600 fps were vastly more accurate when shot at the target. That's not news, but they mysteriously began traveling on a straight path again through the ballistic gelatin. Some even began to exit the back of the tube which was another 4.5" of bullet travel over the soft bullet with the hard nose, peak penetration.

Why? Deformation was zero. Velocity was the same adjusted by load and chronograph. In fact, the lino bullet was 6.2 grains lighter than the pure lead slug used at the beginning of these tests. So, from a reality standpoint, the Linotype slug should have penetrated less material, not more. The answer? Increased RPMs baby! Increased? :grin:

When accuracy peeks, (at the first accuracy point) RPMs peak. RPMs remain the same for a short velocity increase and then eventually they begin to decline as velocity continues to increase. The guess is that the bullet fails farther and farther back on the design to induce rotation upon exit also resulting in a poor accuracy reducing result. But I don't have to be right in my guess, only dispel theory or wives's tales. I suppose that if pushed hard enough, or with low enough rifling, that RPMs could theoretically go to ZERO. This makes the discussion of RPMs a low effect phenomenon, not a HIGH one. And this turns the discussion to a lead strength issue and the ability of the gun to impart rotation issue during a controlled launch.

So what does this explain or dispel that we deal with everyday on the board?

Well this supports the old timers belief that the longest barrels were best for lead. And I suppose that this is because a fully accelerated bullet is experiencing no rotational acceleration at muzzle exit. So, in effect, it has higher RPMs because it is in effect stronger as it leaves the bore. It also explains the use of slower twist rates adding to bullet strength or launch capability. As it turns out, the slower twist rate barrel can be launching at the higher RPMs when compared to a faster twist rate barrel at the same velocity. Particularly in barrels that are too short in relation to case capacity to bore diameter to achieve enough acceleration before exit. It also supports low muzzle pressure upon exit and the use of faster powders for lead which can be said to be sort of the same thing.

It explains worn rifling height issues with older / worn barrels. It explains why different people can shoot the same load at the same velocity inside what is commonly thought of to be the cast bullet (RPM) zone and still get different accuracy results. It explains the failure of PB designs at around certain velocity (RPM ) levels. It also supports old timers bullet design beliefs of wider base bands on their PB designs. There is much more here, but I have already lost many folks who will need to read this again and digest it accordingly if they truly ever can. Cause it is cast boolit heresy.

What does these tests dispel? Well it dispels the high RPM theory for causing wild trajectories beyond a certain point. Accuracy loss occurs ONLY because enough forward velocity is lost that stable flight is no longer possible from a " TOO LOW " RPM condition at the ballistic coefficient / wind resistance level it is traveling. It also dispels the matching bullet to twist rate theory, as a heavier bullet that goes slower than a lighter one, has more surface contact with the rifling to which to impart and maintain rotation / RPMs during acceleration .... at an equal bullet hardness. It helps to explains short barrel finickiness compared to longer barrels, especially in handguns.

This unscientific testing (:grin) essentially turns the cast world upside down on many accepted issues. And while I freely admit that it doesn't explain everything, it doesn't have to. Only to force people with other theories to look to another coarse. It can serve as an example to the futility of scientific testing that results in a false conclusion. No matter how good or scientific a test really is. At least it can alter methods for those who will continue the search for truth which doesn't exist.

There it is in a description of how it was conducted so that it can be repeated. Anyone care to offer an opinion on my methods or conclusion? Ahhhhhh please, somebody! :grin:

[felix]

Looks very familiar, John! ... felix

[rbuck351]

If I understand what your saying, there may not be the rpm limit that has been suggested. That we are not actually getting the high rpms at higher velocity that theory would suggest because bullet strength is not there and the bullet is sliding and not getting the rpms a given twist velocity would suggest. If this is what you are saying, I agree. The reason I think this because when paper patched using the same alloy the rpm "limit" is much higher. How could this be if what you say is not true. I have been pondering this ever since I first read this rpm limit theory. Wondering why a paper patch that has no effect outside the barrel would allow much higher velocity, rpms and accuracy. I believe you have got it. Unstable bullets would not penetrate as well as stable ones.

[NHlever]

Hmmm, 1000 fps with a 1-12" twist is 60,000 fpm (feet per minute), and also 60,000 rpm. 2000 fps is 120,000 fpm, and 120,000 rpm. There is no speed point where this relationship changes as long as the bullet is strong enough to withstand the rotational forces against it. Rotational speed also diminishes much, much more slowly than the forward motion of a projectile. So, if you push a boolit faster than the strength of the alloy used will support you will get skidding, and less rpm than you would with a stronger boolit which is what you perhaps saw when you went from the soft body to linotype. Even jacketed bullets will exhibit skidding if pushed hard enough, quickly enough. The longer one can take to bring the boolit up to rpm (ie longer barrels) the softer the alloy can be. A slower twist helps too, but will not create the same rpm as a faster twist unless the boolit is pushed faster. There is no point in a boolits acceleration where rpm's stabilize, or decline......... while it is in the barrel being spun. As soon as a boolit exits the bore, it starts to decelerate, and so the rpm will drop, but at a much slower rate. Yes, bullets that are spinning very fast, and are stable penetrate deeply, and straight. Look at how well the little 6.5's. and 7mm's did in Africa for proof of that. Fast twists also aid expansion as shown by the old Colt .38 special revolvers when compared to the S&W"s.

Interesting subject.

[felix]

Folks who have killed many deer will claim truthfully that a 32Special (Winnie levergun 16 twist) will kill more quickly than a 30-30 (Winnie levergun 12 twist). The velocity of each is practically the same. The width of the fish-tail after deer entry would be more than the mushroom of the 30-30? Perhaps an appropriate conclusion for the observance.

Yes, indeed, boolits strip. We need a chrono that can accurately measure both speeds, foward and rotational. ... felix

[Rockydog]

BA, Very interesting theory. Would this theory then explain the accuracy of one powder vs another? A powder with a slower curve to peak pressure might allow a bullet to accelerate more smoothly and hold the rifling, gaining RPM. Almost like a car geared to control wheel spin and apply maximum friction to the road accelerating faster than a car of the same horsepower with uncontrolled wheel spin.
To throw another variable in the mix; what happens when you use a gain twist barrel? Or preengrave the bullet by front loading through a false muzzle like they used to do with Schutzen rifles. I believe I read that, even after cartridges were common, they front loaded these and used the cartridges only for the powder charge. I would think that this would tend to get the bullet spinning without so much tendency to slip. Perhaps they knew something we forgot. RD

[felix]

RD, please allow me to interject here, so John can expound on my thingie as well.

Yes, the acceleration curve is the most important aspect in controlling the boolit's faithfulness to follow the path. Altering the powder and primer combo changes the curve, as well as seating pressure. Best to seat off of the lands until a satisfactory power and primer combo can be found to work in the ballpark. Neck friction (BR guns) should be slight to slip-fit during the selection. If no combo can be found, then seating friction (width/length) should be increased to allow for a slower powder.

The problem with customary gain twist is with the deciphering of the gain rate. Using your car example, you will note that most drag racers blow the engine sometime after "ignition" and somewhere unpredictable down the strip (barrel). However, a quarter inch difference between the chamber and the muzzle can be a benefit, as shown in some BR matches. The technique keeps the rifling machine honest in not creating any accidental reverse twist which is catastrophic accuracy wise.

... felix

[runfiverun]

What does these tests dispel? Well it dispels the high RPM theory for causing wild trajectories beyond a certain point. Accuracy loss occurs ONLY because enough forward velocity is lost that stable flight is no longer possible from a " TOO LOW " RPM condition at the ballistic coefficient / wind resistance level it is traveling. It also dispels the matching bullet to twist rate theory, as a heavier bullet that goes slower than a lighter one, has more surface contact with the rifling to which to impart and maintain rotation / RPMs during acceleration .... at an equal bullet hardness. It helps to explains short barrel finickiness compared to longer barrels, especially in handguns

john:
as you know ,this is exactly the opposite of how i have/had it figured.
i KNEW and still do that there is a relationship here between rpm and momentum,but you are showing the opposite of what i thought happened.
the rpm helping effect how a j-bullet works in an animal i put together long ago as i shoot the 7x57 and it's variations and rely on this to work with a lighter bullet at higher launch spped and still keep ranges short for pass through with expansion.
but for cast with accuracy this is gonna take a bit of thought and retesting.
damn you.

[looseprojectile]

I am sure that in all my cast boolit experience I have never seen a boolit that was completely striped by the rifling in a gun bore. Maybe if the grooves were completely filled with lead this could happen.
I suspect that in a moderately clean bore that the boolit will always exit the muzzle with the spin and velocity in sync with each other. I have seen the evidence that a boolit did skid some when starting in the rifling but at some point it had to follow the rifling twist. Otherwise the boolit would come out of the barrel bore diameter rather than filling the grooves.
Perhaps I am just not shooting my boolits outside the box?
Splain some more how the boolit can spin at a different speed when the velocity stays the same.
This ain't April 1st. is it?

Life is good

[Nelsdou44]

I'm with Rockydog and Felix about acceleration. After the boolit becomes engraved into the barrel acceleration is the force that strips the boolit and as I gather from Bass's experiment, rotational velocity suffers.

I see it as a pitcher's arm accelerates through the throw his grip on the ball slips and the ball is released with less spin and subsequent loss of control.

You can over-accelerate a boolit with slower powders too despite keeping the chamber pressure under the limit of the alloy. I've done it and have been scratching my head about it until I read Bass's post. Lessening acceleration as the boolit approaches the muzzle and lower muzzle pressure is a good thing.

Nels

[rbuck351]

I'm not sure you can tell by looking at a recovered bullet when or where in the acceleration that it stripped or how much. If pressure is high enough it could be bumping swageing what ever you want to call it and still skidding out the end of the barrel. You can take one of the bullets that starts loseing accuracy at say 2000 fps and paper patch it and gain several hundred fps with accuracy. So how does the same bullet shoot good at a much higher rpm (much higher than the supposed rpm limit) just by riding paper down the barrel. The only answer I can come up with is that it's not skidding and the added rpm adds stability and accuracy.

[rbuck351]

I'm not sure you can tell by looking at a recovered bullet when or where in the acceleration that it stripped or how much. If pressure is high enough it could be bumping swageing what ever you want to call it and still skidding out the end of the barrel. You can take one of the bullets that starts loseing accuracy at say 2000 fps and paper patch it and gain several hundred fps with accuracy. So how does the same bullet shoot good at a much higher rpm (much higher than the supposed rpm limit) just by riding paper down the barrel. The only answer I can come up with is that it's not skidding and the added rpm adds stability and accuracy.

[Bret4207]

Interesting. I'm a fence sitter of the RPM theory. I think there is an RPM limit for a given material. I'm sure most of us are familiar with the lightly jacketed 22 cal bullets vaporizing when pushed too fast. I'm just not sure how that relates to lead alloys and where the boundaries are.
What Bass says makes sense, but so do a lot of other theories.

Could this be another of those, "Well, in this particular situation this happens, but not always..." things?

[Whitespider]

When accuracy peeks, (at the first accuracy point) RPMs peak. RPMs remain the same for a short velocity increase and then eventually they begin to decline as velocity continues to increase... I suppose that if pushed hard enough, or with low enough rifling, that RPMs could theoretically go to ZERO.

I don’t buy your conclusion. Unless the projectile is skidding, or stripping, through the barrel that would not be possible. If it’s stripping enough to reduce rotation, your barrel would be loaded with lead deposits.

Projectile rotational speed (at muzzle exit) is directly proportional to muzzle exit velocity, that’s just simple physics. A projectile exiting a 1:12 barrel at 1000 FPS is rotating at 12,000 revolutions per second, or 720,000 RPM, at 2000 FPS it’s rotating at 24,000 revolutions per second, or 1,440,000 RPM. This simple fact can not be, according to the laws of physics, challenged or disputed. A projectile will begin to shed velocity and rotational speed as soon as it exits the muzzle; but at your 50-yard test range the rotational loss would be almost nil, even with a badly deformed projectile (time of flight would be way, way, way less than a ¼ second).


What happened was amazing and a truly key point!!!. Penetration peaked, when accuracy peaked. Now why?
At 1400 fps, the penetration was clearly no longer straight line. The slug began to veer off coarse...
The Linotype bullets at 1600 fps were vastly more accurate when shot at the target... they mysteriously began traveling on a straight path again through the ballistic gelatin.
Why? Deformation was zero. Velocity was the same... In fact, the lino bullet was 6.2 grains lighter... So, from a reality standpoint, the Linotype slug should have penetrated less material, not more. The answer? Increased RPMs baby!

No, I don’t believe increased rotational speed produced deeper penetration; I believe projectile stabilization produce deeper penetration.

The rotational speed imparts terrific centrifugal force to the material of the projectile, and if it’s soft enough it will deform and destabilize (or wobble) in flight. This deformation is (or can be) very tiny, and with the elasticity of lead, could return to round as rotation speed decreases. As velocity increased (adding more centrifugal force and deformation), and accuracy decreased, the projectile was hitting the water jug at a less perfect point-forward trajectory, further destabilizing it. In effect, the projectile was entering the gelatin at a slightly sideways profile, exposing more of its side surface to resistance, which would slow it faster and produce directional changes.

The linotype projectile, made of stronger material, was able to withstand a higher centrifugal force before deformation occurs. This kept it at a more point-forward attitude (better accuracy) at higher velocity, resulting in the straight line deeper penetration.

At 1600 FPS, and at only 50-yards, both the pure lead and linotype projectiles were spinning at the same RPMs when they hit the water jug. It was the stabilization/point-forward factor that produced the straight-line deeper penetration.

Hey, but what do I know?

[44man]

As long as velocity is increased, spin will always increase. There is no velocity point where a bullet will lose spin when velocity is being increased as long as the rifling is engaged.
Long barrels were popular with black powder and overbore magnums to allow all of the powder to burn in the barrel with less powder leaving the muzzle to burn in the air. More powder adds to the bullet weight also and can effect velocity. Add more and more black powder to say a 45-70 and velocity will decrease. This is something that can be seen using Pyrocrap. Compress more and more in the case and you will see chunks exit the muzzle like flares. Velocity goes way down.
A barrel can get too long for the powder charge. Then bore friction will slow the bullet if the powder is no longer burning and gas expansion has stopped.
Penetration is affected by spin because of it's effect on stability. Over spin and as soon as a bullet contacts anything it can veer or start to tumble. Bass is correct there because the most accurate load for the gun and bullet will track the straightest.
Bullet shape has a greater effect on penetration and how straight it travels. Pointed bullets are more effected by over spin. A round nose is better and the best will be a flat nose if spin is right. How a nose is deformed is the worst if it does not deform evenly.
Velocity has a great effect and normally the faster a given bullet hits the less penetration you get because of increased pressure build up in front of it. Even worse if there is expansion.
We have shot many things with revolver boolits with large meplats and never had any go off course. I shot a WFN through 10, one gallon jugs of water and the hole out of the last jug was centered. Even shot through a 16" tree or an animal shows a straight path.
I shot this boolit through 37" of wet phone books and the path was straight.
But then the faster I drive these boolits, the less damage is done in deer but I never lose enough penetration to see because the boolit does not deform. The pressure wave in front of the flat nose is moving tissue out of the way, unlike a different shaped bullet or one that expands and slows.
There is just a lot more to this then Bass has found. I have learned more by letting professor deer show me.
Bass is a little off with some of his thoughts. :Fire:

[44man]

Whitespider has the correct view of this. :drinks:

[felix]

The word strip must have consistent meaning here. Strip means the projectile goes through an interrupting change in twist force, however small, which is not commensurate with the acceleration of the projectile at that instant. ... felix

This explains the reasoning behind "seasoning" a barrel, and why some barrels will print to point of aim on the first shot, and others won't. This is also why some lubes will shoot "screamers" with a certain load and others won't. ... felix

[mrbill2]

Whitespider on the money.

From Hatchers Notebook
First Picture: Penetration of 32.5 inches of oak by 3006 bullet weighting150 grs. at 2400 fps. Range 200yds.
The range was long enough so that the bullet was sufficiently stable to continue point first and thus give good penetration.

Second Picture: Penetration of 11.250 inches in oak by 3006 bullet at 2400 fps. Range 50 feet. The penetrastion is mush less than achieved at longer ranges. Reason is that at the short range, the bullet has not settled down to a stable flight, and when it encountered the resistance of the oak it was yawed badly, and rapidly gave up all its energy.

Mr. Bill

[44man]

Wonderful guys. :drinks:
Velocity can be a friend or an enemy depending on the gun, bullet and distance. There is no answer that works for all.
All the testing we did was for fun and means nothing in the real world of hunting.

[looseprojectile]

Whitespider and 44 Man have splained it to you.
In my opinion, the most important thing to strive for is to present your boolit to the world, STABLE, at the exit from the muzzle of the gun. Of course it must remain or be stable at the target. In between don't matter.
If the boolit strips in the rifling it is not right. The powder is not right. The twist is not right. The speed is not right. The size is not right. The alloy is not right. The lube is not right. The boolit length is not right.
All these things and more are interelated.
Making and shooting cast boolits is a very exacting art/skill, if you want to do it well, and a lot of people just want to shoot cheap without all the effort and planning. I will always try to encourage new shooters and casters to start with proven boolits and loads so they don't get discouraged at the begining.
Kenny Wasserburger and other good shooters would seem to have a handle on making and shooting cast boolits and I am sure they would tell you that the trigger jerk has a lot to do with the whole process. That is even after you get the load as good as anyone can.

Life is good

[NHlever]

Whitespider....... I think you might be using inches, and feet mixed in your math...... I could be wrong about that since it has sure happened before! :D

[44man]

His figures are off but what he said is correct. I seen it but it is not important. :mrgreen:

[Pat I.]

The word strip must have consistent meaning here. Strip means the projectile goes through an interrupting change in twist force, however small, which is not commensurate with the acceleration of the projectile at that instant.

What the heck does this mean?? Strip always meant that the bullet jumped the rifling to me, but maybe that's what it does means.

[felix]

Yes. it does. ... felix

[Larry Gibson]

Whitespider nailed it; “No, I don’t believe increased rotational speed produced deeper penetration; I believe projectile stabilization produce deeper penetration.”

looseprojetile's call of "BS" was a good call.

BTW people; Bass’s experiment has nothing to do with “dispelling” the RPM threshold so don’t be confused like Bass is. In fact it only gives further evidence that the RPM threshold is real. Bass states the velocity was limited to 1600 fps with the softer bullets because accuracy was getting bad and would exceed 2 ½” at 50 yards if a higher velocity (and thus a higher RPM) was used. Well guess what? Bass was exceeding the RPM threshold for those soft lead bullets. It is as simple as that!

Larry Gibson

[44man]

We think of the rpm's being exceeded after the boolit leaves the muzzle but it also happens while the boolit is in the bore, skidding too much and opening gas channels around the boolit.

[Whitespider]

Oooopps... :oops:

Correction;
Projectile rotational speed (at muzzle exit) is directly proportional to muzzle exit velocity, that’s just simple physics. A projectile exiting a 1:12 barrel at 1000 FPS is rotating at 1,000 revolutions per second, or 60,000 RPM, at 2000 FPS it’s rotating at 2,000 revolutions per second, or 120,000 RPM.

[Pat I.]

Yes. it does. ... felix

You must be the life of the party at a barbecue. :-D

[303Guy]

A small point that has been overlooked here is that the boolit can deform as it exits the muzzle if the muzzle pressure combined with rotational forces are too high. That's because the bullet is 'bumping' up, unsupported by the bore. That requires a fairly high muzzle pressure but remember that the boolit surface is pretty well heated and softened by the time it reaches the muzzle. That's why paper patching works - it keeps the lead cool. (Among other factors).

On the 'stability - penetration' issue, in the days when Holland & Holland introduced their 375 magnum, there was an issue of close range penetratration being poor due to bullet yaw. At longer ranges when the bullet had settled down penetration was good. My Rhodesian Uncle was involved in trying to persuade Holland & Holland to make ammo with a heavier and more muzzle stable load. Eventually, someone did.

[felix]

Yep, to both of you: pat and guy! I've blown up several condom 22's at 3800 plus. The lead smoke is really something to see in mid air down around 50 yards. Was the projectile expanding at the nose because of air friction, or was it because the lands were too sharp for that skinny jacket during acceleration? Maybe both? ... felix

[303Guy]

Was the projectile expanding at the nose because of air friction ...?Is it possible that the bullet actually deforms inside the bore due to inertial forces, which could do two things - upset the nose and heat the jacket to near failure point and of course deform further as it exits? Just speculation of course. I have had tight j-words with light charges actually stopping in the bore then dropping out when cooled. These show heat staining and some that did not stop melted into the catch cloth.

http://i388.photobucket.com/albums/oo327/303Guy/MVC-462F.jpg

[leftiye]

303, bravo! There are many here who will swear on their mother, in church that heat doesn't happen to bullets in the bore. (I'd bet that air cools a bullet during flight until very high velocities are undertaken) Good pictures! BTW folks, 303's bullets arent' going very far or very fast before he catches them.

I think we need to take another look at Bass's test with attention focused more on deformation in the barrel, and subsequent instability. One needs to ask themselves -"Does one blame rpms for innacuracy or do they blame the deformations that rpms must have present to have any effect?" The effects that Bass saw happened at the point where deformation was starting to happen. If you want to exceed Larry's predictions, all you have to do is throw an undeformed boolit that hasn't been incorrectly launched (reads point on, and properly stabilized - overspinning doesn't necessarily destroy accuracy either).

[rbuck351]

Some of you are assuming that the bullet is not still skidding at the end of the barrel because there is no massive leading, yet skidding, presuming at the start, does not necessarily cause massive leading. Some still needs to explain why a paper patch allows much higher velocity and rpm with accuracy with this same lead bullet that just won't take the rpm. Once more, Why does the paper allow much higher rpms with the same alloy? I think it's because it is not skidding and actually getting enough rpm to stabalize.

[HangFireW8]

All of this was fired from my 30-06 at 50 yards which is unimportant, except it establishes a base line.

You say it is not important, but it is.

"Settling time" explains why US Army tests of the .30-06 showed that it penetrated more wood at longer ranges than shorter ranges.

Which, goes a long way in explaining some of your results.

-HF

[Whitespider]

rbuck351,

I’ve never been a big student of paper patching; but the obvious answer to your question is that the paper acts in much the same way as a bullet jacket. It insulates the lead from friction, heat, gas cutting and the gouging, cutting and deformation during the engraving of the rifling, all of which will weaken the “constitution” of the lead. Also, if the paper patch remains on the bullet during flight (does it?) it would be further strengthening the outer skin of the bullet, at least until the bullet settles in. In a nut shell, the paper allows the bullet to exit the barrel closer to a pristine condition than a non-patched bullet, which would allow it to withstand greater rotational forces before deformation would occur.

[looseprojectile]

Is this sorta like gear teeth skidding? Never heard of such a thing.
This brings up another thought. Does a boolit, when fired, accelerate in a smooth increasing velocity fashion or does it slow and speed up several times on it's way?
This may be where Felix gets his skidding, acceleration, stripping thingie. I remember reading, maybe here that someone theorized that a boolit/bullet might slow and speed up several times on it's way out of the gun.
I still postulate that if your boolit is skidding or stripping something ain't right.
At least Bass has done some testing and arrived at some conclusions and that ain't all bad.
I, for one, have a hard time wrapping my brain around a boolit accelerating linerally and circumferentially, simultaneously. One thing at a time please.

Life is good

[Larry Gibson]

I don't buy into the "bullet skidding" either. There is some initially if the bullet must jump to the rifling but I've never heard of nor seen any proof of a bullet "skidding" onece it's been fully engrave and engaged by the rifling.

rbuck351

Whitespider pretty much answers your question.

looseprojectile

Appears that some times a bullet does "slow and speed up several times on it's way". I base this on observations of numerous (not all by any means) loads time pressure graphs. Most are relative smooth up and down but some are not.

Larry Gibson

[siwel]

If I'm understanding correctly, a bullit fired straight up into the air in perfect conditions is going to quit spinning at the apex?

[Slow Elk 45/70]

I have a 22-250 with 28" match grade bbl that can be loaded up to +4000fps with the right powder and J condoms...some of these loads will leave a smoke trail that you can see...but never touch a 100 yard target. The bullet vaporizes , is this from over revving RPMs or too light construction of the jacket, for the velocity , or maybe all the above .

I can back it off 2 gr of powder and it shoots fine, so ???

This is just something that I have experienced, no biggie, I had not thought of the RPM theory, I just assume that the bullet is not tough enough for the velocity./

This is an interesting thread...makes you consider other things that may affect your loads, cast and otherwise

[leftiye]

Siwel, Nah, but it will land spinning on its ****.

Rbuck, Whitespider has a pretty good grip on why the paper patched boolit can be fired at much higher velocity (and rpms) than the naked boolit will "lose it" at. It prevents deformation, leading, and stops the lead from softening. The culprit isn't rpms, it's the overheated, therefore weak, and deformed, - naked boolit. (more correctly, the things that it is susceptible to - to include skidding)

[Larry Gibson]

If I'm understanding correctly, a bullit fired straight up into the air in perfect conditions is going to quit spinning at the apex?

Negative, as mentioned it will still be spinning and that s"spinning" will have slowed very little. Converesly the velocity will have stopped completely.

Larry Gibson

[Larry Gibson]

Leftiye's problem is that he can't differentiate what happens to the bullet inside the barrel vs what happens to it outside the barrel.

The deformation to the bullet inside the barrel during accelleration is the reason the RPM via centrafugal force has the adverse affect on accuracy outside the barrel. Fairly simple concept that all but a few understand. However to give leftiye some credit he is correct in that deformation of the cast bullet is "the culprit". The centrafugal force of the RPMs is just what causes the "culprit" to go bad. If we can control the deformation of the bullet during accelleration then we can bump the RPM threshold upwards. However, at some point the adverse affect of the RPM threshold will occur and be obvious through decreased accuracy and the non-linear group dispersion as the range increases.

Larry Gibson

[rbuck351]

White spider If the alloy is that close to destruction that a thin piece of paper protects it, then added speed and pressure may be causing skidding further than at engraving, maybe even to the muzzle. I also don't think .004 of paper is insulting that much. Paper is quite a bit harder than lead and would allow much less skidding. Does the paper stay on much past the muzzle? I doubt it, as most that patch find the pieces right in front of the muzzle and I've never heard of anyone finding patch at the target.

looseprojectile " like gear teeth skidding" Yes, imagine a lead pinion gear in an auto rear end if you want to see skidding. If it's skidding something isn't right. Yes again. Too much acceleration, pressure and too soft of alloy and we get skidding.

Larry I've never seen any proof that skidding doesn't go to the muzzle nor that it does.

leftiye I don't think the pp bullet is any different than the non pp after it leaves the muzzle except that it may be spinning faster which according to some should make it less stable. But, it must in fact be more stable. Larry If two of the same bullets leave the same barrel at the same speed they should be equally stable if the rpms are the same. But the naked bullet will fail before the pp one. So maybe it's not getting the rpm of the pp. I think the deformation you speak of is skidding and because of the plastic nature of lead I believe it may go to the muzzle and less vel and rpm than you would expect and loseing accury and stability sooner than expected.

More rpm= more stability=more penatration=more accuracy until the bullet starts to come apart from inertia.

[303Guy]

Here is a pic of a boolit fired at near max pressure and velocity for a g/c boolit. 220gr @ 1900fps give or take.

http://i388.photobucket.com/albums/oo327/303Guy/MVC-657F.jpg

Here is a boolit fired at similar pressure and velocity that shows signs of 'slip'. this is due to the barrel being a two-groove. The width of the groove is double what is left on the boolit.

http://i388.photobucket.com/albums/oo327/303Guy/MVC-644F.jpg

One can see on the boolit the degree of wear on the thrust face. The boolit did not actually slip.

I have had boolits strip in the bore - they hit the target sideways! Boolits that do wobble in flight still show the rifling on paper targets. I personally think there is simply no way a boolit that has stripped or 'slipped' or 'skidded' is going to hit a target nose on. Think of this one; when a muzzle gets worn, the rifle will shoot very poorly with obvious sign of yaw on a paper target. Cut off the worn tip and re-crown (even with a file) and the yaw disappears and groups tighten up. So how is a boolit that has lost it's integrity in the bore going to shoot straight? Now if that boolit has 'skidded' it will not have sufficient spin and it will be loose in the bore (I think). The only way to achieve any accuracy is to maintain a tight fit in the bore right to point of exit.

We should ask Bass what the rifling impressions on his recovered boolits looked like. Pics would be real nice.[smilie=1:

[45 2.1]

One needs to ask themselves -"Does one blame rpms for innacuracy or do they blame the deformations that rpms must have present to have any effect?" The effects that Bass saw happened at the point where deformation was starting to happen. If you want to exceed Larry's predictions, all you have to do is throw an undeformed boolit that hasn't been incorrectly launched (reads point on, and properly stabilized - overspinning doesn't necessarily destroy accuracy either).

At least Bass and Leftiye understand whats actually going on.



The deformation to the bullet inside the barrel during accelleration is the reason the RPM via centrafugal force has the adverse affect on accuracy outside the barrel. Fairly simple concept that all but a few understand. However to give leftiye some credit he is correct in that deformation of the cast bullet is "the culprit". The centrafugal force of the RPMs is just what causes the "culprit" to go bad. If we can control the deformation of the bullet during accelleration then we can bump the RPM threshold upwards. Larry Gibson

Several of us have been doing what Larry suggests for quite some time. When Larry learns how to negate incorrect launch, he should see his proposed theory is really poor methodology. Keep working on it Larry, you live long enough you might find out how to do it.

[Bass Ackward]

Wow. Some very interesting replies. I was expecting more degeneration into argument. I must admit I am shocked.

Look. None of these bullets exhibited stripping except at the GC. What I believe happens is that the bullet leaves the confines of a stable environment where air flow is controlled away from the slug. When that slug begins to exit the bore, a new air flow pattern begins to be established. Along with this new air flow pattern is breaking the barrier where frictional forces cause violent reaction which is why bullets have to go to sleep. This is the reason for the rotation.

But as your slug exits. Less and less of your bullet is in contact with the rifling until eventually, the base is the only thing imparting rotation into this new environment. If you have a PB, you are going to have a lower velocity limit than with a GC. Then what if your bullet has to pass over fouling? You lose valuable surface area with which to maintain this grip. Not only that, but you begin to release pressure which not only distorts the forming air flow pattern compared to the round before it, but it is going to kick the base off in the opposite direction as soon as it clears. This will require more distance to form the sleep pattern along with everything Larry likes to point out about bullet balance that has some play on things too. Everything has a part or effect. Just not as much as some folks want to focus on.

But the limits on a GC are the depth of the rifling which establish the bite into the lead below it. Low height, low bite. If the lead is soft, then you are going to have less strength in what is bitten than if it was hard. I have had loads where GCs were always found on the slugs. I have had loads where you never found one. So the old problem of GCs coming off in flight, is that they are coming off, or are they being ripped off? And then we get into questions about hard GCs vs soft. Which one forms a better bite? Want to try lube fliers? And a slower twist angle would mean, in effect, a stronger base to get a better launch.

And then as we continue to push faster, the only logical conclusion is that the bullet begins to fail farther and farther up the slug which would make it look like it occurred in the bore when it was really external if you understand what I mean. This can change the approach we might want to take. But outta balance had little to do with this test. And the low RPMs had little effect on it because I was even WAY below the zone where anything is supposed to work if you buy the RPM theory. The launch simply was worse that the slug needed more time to stabilize which hadn't happened yet.

Because accurate flight at high velocity IS possible. Certainly above what is accepted. There has to be evolving factors that simply aren't available to us. But if RPMS spins a bullet off into oblivion because of outta balance and RPMS, it wasn't true at this level. This was simply a failed launch for what ever reason you buy. Don't like my explanation, make your own.

Are these theories correct? Yea right. What if I had done them more scientifically and fired 10 shots at each? Would the results or my suspicions be any more credible? Would it have swayed ANYBODY if it had? :grin: Doubtful. Scientific study of chaos and changing chaos is a difficult thing. A straw can be driven by wind into wood. If you drive anything fast enough, it will stabilize until a "certain" amount of velocity is lost and then it will act as a non rotating object. But the accuracy will never be as good as if the launch and rotation were actually there.

What this did do was alter my thought processes for hunting. The excitement and groundbreaking stuff was a joke for those that know my positions. No rules means that you don't get excited about anything here and take it all with a grain of salt. But to actually see it happen, WAS kind of impressive. Again, I have to let this pass and take it for what it is worth if anything. Cause it doesn't stop. Does longer, heavier bullets shoot more accurately at lower velocities because they reach farther (have more time) to pass through the barrier with enough lead contact (stronger) in the bore to launch better? Do heavier cast fail quicker than light bullets at high velocity because the effects of weight are accumulative on the base where stripping is paramount? (easier to rotate a light one) This will go on for awhile for me in my mind until I can disprove it or explain it away as a variable.

Thanks for the posts.

[44man]

I have a 22-250 with 28" match grade bbl that can be loaded up to +4000fps with the right powder and J condoms...some of these loads will leave a smoke trail that you can see...but never touch a 100 yard target. The bullet vaporizes , is this from over revving RPMs or too light construction of the jacket, for the velocity , or maybe all the above .

I can back it off 2 gr of powder and it shoots fine, so ???

This is just something that I have experienced, no biggie, I had not thought of the RPM theory, I just assume that the bullet is not tough enough for the velocity./

This is an interesting thread...makes you consider other things that may affect your loads, cast and otherwise
I used 60 gr Hornady bullets in my 220 Swift long ago and never had one damaged in flight but if I cut off one blade of grass in front of a target, the target would be sprayed with pieces. A lighter made bullet would sure blow up in the air.
The Swift had a faster twist then the 22-250.

[44man]

A question to think about with bullet heat. Jacketed bullets get hotter because they have more friction in the bore. Lead has less and paper patched less yet.
What about barrel time?
A jacketed shot real slow is in the bore longer and might get hotter.
I have picked up thousands of bullets and never seen the heat discoloration on the metal 303guy shows. So what is causing so much heat?
We know it is not from the powder, only friction. But can a slow bullet soak up more heat from the hot gas? Is the brass case hotter if touched right away? Does the barrel heat faster?
Does testing a rifle way out of bounds from normal function prove anything?
You have it, my monkey wrench for the day! :bigsmyl2:

[Whitespider]

rbuck351,
You said it, not me, “Paper is quite a bit harder than lead and would allow much less skidding.”
Well going with that theory, I contend that the gas check (which I assume Bass was using) is harder than paper, so once engaged to the rifling it would prevent the supposed “skidding” better than a paper patch.

Also, I’d rethink my statement, “ I also don't think .004 of paper is insulting that much.”
Paper is an excellent insulator, many times better than the copper used in bullet jackets. Mulched paper has been used as insulation in buildings for years because of its extremely high R-value to weight ratio; paper sheeting was even used as insulation on electrical wiring years ago (my 100-year old farm house has paper insulated wiring).
Try this, heat a couple of boolits in your oven to say, 250-degrees, drop one in your bare hand and see how long you can hold it; now insulate your hand with .004 of paper and see how long you can hold the other hot boolit. When you consider that the boolit’s travel down the bore is measured in just milliseconds, well...
But there’s more. Paper patching of .004 protects the boolit from the effects of friction and some of the deformation of rifling engraving, as well as adding strength to the outer skin. And don’t forget, .004 of paper patch is actually .008 of protection from the rifling deformation, because it does so on both sides, or more precisely, around the circumference of the boolit. A paper patched boolit is a condomized bullet; the condom is just made of different material than copper.

And you stated, “Larry I've never seen any proof that skidding doesn't go to the muzzle nor that it does. ”
Well I have, I’ve only been casting for about 4-years, but I’ve been shooting cast for over thirty years on my backyard shooting range. Until he moved because of a job change, I got most of them from a local friend that would custom cast for me. I’ve also bought many commercially cast and many soft swaged lead. I’ve shot them from countless handguns, several .30 caliber rifles and a couple .45 caliber rifles. I’ve shot alloy soft enough to chew and some cast from 100% Linotype, with and without gas checks at velocities and pressures that run the full gamut. Every spring, after the snow melts, I walk my range and pick up hundreds of boolits just lying on top of the ground. Most, except for the rifling marks, look undamaged; good enough to be loaded and fired again. I have never seen any evidence of “skidding” on the center or rear driving bands of any recovered boolit. Occasionally, rarely, I will see just a tiny bit of widening of the engraving on the front driving band of softer boolits.

Simply, I don’t believe, and can not be convinced, that the velocities (pressures) that Bass used in his test(s) could have possibly produced the supposed “skidding” you advocate. I don’t believe a boolit that has “skidded” through the bore will do any thing but tumble once it exits the muzzle.

[felix]

I actually "caught" a flying BULLET, 220 Craig round nose, as it bounced back from going through organic trash. Total distance from muzzle was about 80 yards, which includes maybe 50 yards from gun to junk pile. I was standing off to the side about 30 yards from the impact area. Muzzle velocity: 308W case full of 5010 using Mod 99 levergun. Caught velocity about 10 MPH. Result? Impossible to hold the bullet because of the heat; actually caught and dropped immediately. Did not cool enough to hold until 5 minutes later. Land marks were perfectly uniform and appeared undamaged. ... felix

[44man]

I shoot heavy boolits in my revolvers and a heavy boolit is harder to get the rifling to overcome inertia. All of my recovered boolits show wider marks on the front but at the base the marks are bore size. That is what counts most. A good base seal has to be kept.
I have to wonder if the wider marks at the front aid lubrication? [smilie=1:I get no leading or fouling that builds up after 5 shots or 200.
Accuracy is top notch.
Soft lead started fast will skid a long way, get gas cut, out of balance and will leave the muzzle funny. A gas check will not save you, neither will a paper cover.
The pointy boolit Lee makes for the 45-70 has been reported to slump so bad that the boolit is shortened and most of the nose is engraved with rifling, changing the bore engraved length too much.
I want my boolits to be in as cast condition when they leave the bore other then engraved marks.
I would expect the same from a rifle and boolit design, alloy and velocity must be right.
If you are going to change the boolit in the bore why not just shoot split shot or roll round balls between plates until they fit the case? :confused:
Why would so many boolit designs be listed? Only need one! :Fire:

[felix]

I've seen many times a boolit which has skidded enough to widen the land marks at the boolit barrel exit point. Experiment can be set up easily by successively sizing the boolit smaller until the occurance. Try and keep the muzzle velocity the same for each boolit size. These experiments were done during my college years in lieu of going to beer joints, movies as a diversion of my studies. ... felix

[44man]

I've seen many times a boolit which has skidded enough to widen the land marks at the boolit barrel exit point. Experiment can be set up easily by successively sizing the boolit smaller until the occurance. Try and keep the muzzle velocity the same for each boolit size. These experiments were done during my college years in lieu of going to beer joints, movies as a diversion of my studies. ... felix
Just what I said, but the damage was done at boolit entry into the rifling. Fast powder and soft boolits.

[Larry Gibson]

White spider

If the alloy is that close to destruction that a thin piece of paper protects it, then added speed and pressure may be causing skidding further than at engraving, maybe even to the muzzle. I also don't think .004 of paper is insulting that much. Paper is quite a bit harder than lead and would allow much less skidding. Does the paper stay on much past the muzzle? I doubt it, as most that patch find the pieces right in front of the muzzle and I've never heard of anyone finding patch at the target.

I also believe a normal PP is supposed to come off the bullet on muzzle exit. Seems with some use of "tapes" that this might not be the case.

Larry I've never seen any proof that skidding doesn't go to the muzzle nor that it does.

Many of us have recovered bullets for years both from down range and from traps. In all of those recovered bullets I have never seen nor read or heard about one that showed any evidence of this "skidding. Many examples have been found that demonstrate a small amount of it at the front of the bullet proving it happens engaging the rifling. However I've never seen any actual evidence of "skidding". NOTE; Until this thread it was called "stripping". Are we attempting to change the name?

leftiye I don't think the pp bullet is any different than the non pp after it leaves the muzzle except that it may be spinning faster which according to some should make it less stable. But, it must in fact be more stable.

If they both leave the muzzle of the same rifle at the same velocity then the rate of spin is the same regardless if they are PP'd, regular cast or jacketed bullets.

Larry If two of the same bullets leave the same barrel at the same speed they should be equally stable if the rpms are the same.

Correct here but remember that an inaccurate bullet can still be a stable bullet. There are other factors that affect accuracy than just stability. Perhaps this is where some really have a hard time understanding how the RPM threshold works when they believe accuracy is tied to stability alone. It is not. A perfect example is the difference between a typical .30 cal milsurp bullet and a Sierra 168 Match King. When both are fired from say a .308W Match rifle with a 10" twist both bullets are stable, go down range point first, leave nice round holes in the target and have linear dispersion of the group as range increases. Both bullets fall well within the parameter of "stable". However, the milsurp bullet gives 2-4 moa accuracy and the 168 MK gives 1/2 -1 moa. If both are stable then why the variation in accuracy? The reason is there are other forces that act upon the flight path of the bullet. Centrafugal force acting on the non eccentricities (balances) of the bullet is the major one.

But the naked bullet will fail before the pp one. So maybe it's not getting the rpm of the pp.

If both bullets are of the same velocity then the RPM is the same. The adverse affect on accuracy is the centrafugal force acting on the imbalances in the bullet created by accelleration in the barrel or because the bullet was not balanced to begine with.

I think the deformation you speak of is skidding and because of the plastic nature of lead I believe it may go to the muzzle and less vel and rpm than you would expect and loseing accury and stability sooner than expected.

Think what you will but without some sort of definitive proof it is just a thought. As I mentioned, many cast bullets have been recovered by many of us. I will be more than happy to change my mind on this if I could see some sort of proof. Several of us have "put the pedal down" so to speak on cast bullet velocity. I have shot them to 3,000 fps and some (Starmetal for one I believe) have shot them even faster. We could find nor demonstrated any evidence that the cast bullets were "stripping" or "skipping" accross the lands.

Leftiye was correct in an earlier post (he just doesn't realise it apparently) that the bullets are damaged during accelleration inside the barrel. Many bad things happen to cast bullets inside a barrel, especially during high accelleration. Evidence of all of these "bad things" is seen in on the recovered bullets. As stated, I've yet to see any evidence of completed stripping/skidding on any recovered bullet.

More rpm= more stability=more penatration=more accuracy until the bullet starts to come apart from inertia.

It's not quite as simple as that. Many tests have demonstrated that more velocity does equal more penetration but actually results in less penetration. As mentioned; accuracy while dependant on stability is not a function of stability, i.e. there are other bactors as well.

Larry Gibson

[Larry Gibson]

303guy

Did you recover any of the bullets that hit the target side ways? If so they do you have a picture of them? If not then how do you know the "stripped in the bore"? Key holing is not an indicator of "stripping".

Larry Gibson

[Larry Gibson]

Bass

"And then as we continue to push faster, the only logical conclusion is that the bullet begins to fail farther and farther up the slug which would make it look like it occurred in the bore when it was really external if you understand what I mean. This can change the approach we might want to take. But outta balance had little to do with this test. And the low RPMs had little effect on it because I was even WAY below the zone where anything is supposed to work if you buy the RPM theory."

We've been over your obvious misunderstanding of the RPM threshold theory many times. You consistantly criticise it yet you consistantly fail to provide us with a definition of what you think it is. It is quite apparent you do not understand the basic concept of the RPM threshold.

So I will explain it again as it pertains to your test. Your solid linotype bullets were accurate because they better withstood the acceleration of the load and did not deform as much. Hence there was not as much imbalance to the bullets for the centrafugal force caused by the RPM present to adversely affect. On the other hand, your soft lead based bullets obviously were damaged during accelleration to a much greater degree. (you go to great lengths in your post to explain how this happens) They were thus far more imbalanced than the linotype bullets. The centrafugal force from the same level of RP had a greater affect on the increased imbalances of the deformed soft based bullets and thus they were less accurate.

In simple words, the softer alloyed bullets had a lower RPM threshold than the harder linotype bullets. That is why they had less accuracy. The RPM was the same for both bullets if the velocity was the same. That is the way it, perhaps someday you'll understand.

Larry Gibson

[StarMetal]

Fellows I'm posting some pictures of a 70 gr bullet of alloy mixture 50/50 lead/WW water quenched from my 7 twist Colt HBAR AR15. I've been shooting the devil out of this lately and it's taken me quite some time to recover a half decent bullet. As you can see there is no evidence of stripping, skipping...whatever you want to call it on the bullet. The rpm of this particular bullet is way above the 250,000 rpm range. By the way the smallest group I've gotten so far is 1 inch, but not consistent. I was told by a good friend of mine to weigh my bullets which I have not been doing. I can say the inconsistent group is consistent. By that I mean it will shoot five into that 1 inch group and place the others to another position...over and over. I played with lube, seating depth, and different powder....along with different brands of brass. I wanted to recover a bullet to see what it has to tell me. Another by the way I find nothing in my barrel...cleans right out...got to love that chromed bore. Nothing in the gas system either at this high velocity. One more by the way I cannot resist....none of the bullets flew off into wonder wonder land.

Joe

http://i245.photobucket.com/albums/gg51/starmetal47/70grBullet.jpg

http://i245.photobucket.com/albums/gg51/starmetal47/70grbullet1.jpg

[Larry Gibson]

I used 60 gr Hornady bullets in my 220 Swift long ago and never had one damaged in flight but if I cut off one blade of grass in front of a target, the target would be sprayed with pieces. A lighter made bullet would sure blow up in the air.
The Swift had a faster twist then the 22-250.

Slow elk and 44man

regarding bullets blowing up; Take two Hornady bullets, the standard .224 55 gr SP and the .224 55 gr SX which are identical all except for one thing. The jacket of the SX bullet is much thinner. Now load them to the same velocity in a 7-9" twist .223 to 3200 fps or in a 22-250 with 14" twist to 2600+ fps and see what happens. The standard Hornady 55 gr bullet will shoot nice littl groups. The 55 SX will do poorly because many of the bullets will disintegrate in flight before they reach a 100 yard target. The difference is the thinner jacket of the 55 gr SX is not capable of holding the bullet together and withstanding the extreme centrafugal force of the very high RPMs. Fun to watch though!

Larry Gibson

[StarMetal]

303guy

By examining your bullet picture it appears to me that the bullet was undersized to your rifles bore and groove diameter. I say this because the portion of the cannelure crimp groove the rifling (by this I mean the top of the land which is the bore diameter and not to be confused with the groove diamter) did not seem to touch the little cannelure groove at all.

Joe

[Larry Gibson]

Starmetal

What mould are you using?

Larry Gibson

[StarMetal]

Larry,

I'll tell you some reasons why those two 30 caliber bullets print different size groups. If you weigh the two different bullets you will find that the Sierra's are more consistent. If you section the two bullet types you will find that the Sierra's jacket thickness is more uniform all the way around the diameter of it. You mentioned they both fell into that "stable" category, but to me that is a given range with a minimum and maximum, so the Sierra's being the more perfect of the two type is spinning more true then the military. Different weights means different velocities, which means different bullet placement on the target. We won't get into BC's and ogive shapes. Those are just some of the things, by all means not all of them.

Joe

[StarMetal]

Starmetal

What mould are you using?

Larry Gibson

NEI that I've modified.

Joe

[felix]

Good show, Joe! Keep in mind that Larry's RPM dealie is not all wet. It is more enlightening to not think of RPM maybe, but circumference speed. The skin of a 22 at 200K RPM is moving 2.3 inches per second, just like a 30 is at 120K. A 30 at 200K is moving 3.2 inches per second. The reason of looking at the circumference speed is that it is more commensurate with indicating internal stress, i.e., inertia. The more inertia, the more rotational force is required to get the boolit up to speed. ... felix

[StarMetal]

Yep, to both of you: pat and guy! I've blown up several condom 22's at 3800 plus. The lead smoke is really something to see in mid air down around 50 yards. Was the projectile expanding at the nose because of air friction, or was it because the lands were too sharp for that skinny jacket during acceleration? Maybe both? ... felix

You've hit the nail on the head there Felix. I'd like to see a combination where a certain bullets vaporizes with a certain cartridge and rifle....then do the same thing with the same setup EXCEPT the barrel had no rifling. You read that right...no rifling. If the bullet still vaporizes that dispels the rpm doing it. I have often wondered if it was the air friction on the nose of the bullet and the heat it causes that destroys a bullet that is pushed too fast.

Joe

[Larry Gibson]

Larry,

I'll tell you some reasons why those two 30 caliber bullets print different size groups. If you weigh the two different bullets you will find that the Sierra's are more consistent. If you section the two bullet types you will find that the Sierra's jacket thickness is more uniform all the way around the diameter of it. You mentioned they both fell into that "stable" category, but to me that is a given range with a minimum and maximum, so the Sierra's being the more perfect of the two type is spinning more true then the military. Different weights means different velocities, which means different bullet placement on the target. We won't get into BC's and ogive shapes. Those are just some of the things, by all means not all of them.

Joe

Joe

All that is correct with one caveat, actually there are 3 area's of stabilization generally recognised; minimally stable, stable and over stablized. You "telling" me why is simply restating what I stated. If the centrafugal force from the RPM was not there then, given a good "launch" as Bass is prone to say, then all bullets would be equally accurate regardless of inconsistencies. However, the centrafugal force from the RPM IS there so, while both bullets are stable, one bullet (the consistant one) is going to be more accurate than the other one. Yes there are other factors but the two biggest factors affecting accuracy of a stable bullet are the inconsistencies (balance) and the adverse affect the centrafugal force of the RPM has on those inconsistencies (imbalances).

Larry Gibson

[Larry Gibson]

You've hit the nail on the head there Felix. I'd like to see a combination where a certain bullets vaporizes with a certain cartridge and rifle....then do the same thing with the same setup EXCEPT the barrel had no rifling. You read that right...no rifling. If the bullet still vaporizes that dispels the rpm doing it. I have often wondered if it was the air friction on the nose of the bullet and the heat it causes that destroys a bullet that is pushed too fast.

Joe

Joe

No sense wasting your money on a smoothbore:-) Read my post above to 44man and Slow elk. You've the rifles to run that test with using both Hornady bullets (I'll send you some bullets if you can't find any to test). If it is air friction and heat then why does one bullet sirvive and the other doesn't. If it is air resistance and heat why do any cup/core bullets survive above a certain level? The reason is the RPM. Run the test and you will see.

Larry Gibson

[StarMetal]

I'll throw this in here for whatever it's worth. I've always contended that my Colt HBAR with a 7 twist caused more tissure damage on the various animals I've shot with it because the rpm of the bullet was much higher then the norm 12 twist. I don't know how many different forums you all visit, but there is this Naval Ballists/Wound forensic doctor that visits two other forums I'm on. His name is Dr. Roberts I believe. We have disagreed on what I stated earlier in this post. He said to the contrary the faster twist showed less tissue damage or wound damage. I contented that combined with the forward velocity energy and rotational energy (it takes energy to get both of those as we know) that more energy is delivered to the target. In the case of my 22 caliber out of that 7 twist the bullet just literally explodes when it hits the animal. It didn't make much difference if I used 55 gr FMJ Nam surplus bullets or soft points/hollow points. Maybe, in my case, it had more to do with the size of animal the bullet hit????

Joe

[StarMetal]

Joe

All that is correct with one caveat, actually there are 3 area's of stabilization generally recognised; minimally stable, stable and over stablized. You "telling" me why is simply restating what I stated. If the centrafugal force from the RPM was not there then, given a good "launch" as Bass is prone to say, then all bullets would be equally accurate regardless of inconsistencies. However, the centrafugal force from the RPM IS there so, while both bullets are stable, one bullet (the consistant one) is going to be more accurate than the other one. Yes there are other factors but the two biggest factors affecting accuracy of a stable bullet are the inconsistencies (balance) and the adverse affect the centrafugal force of the RPM has on those inconsistencies (imbalances).

Larry Gibson

There is no doubt if the jacket isn't the same thickness all the ways around the bullet that it's going to rpm problems....just like a tire out of balance.

Joe

[felix]

Yeah, Joe, the Doc is correct, as you have speculated by your last sentence in the paragraph above. Think about radiation poisoning from your point of view. ... felix

[StarMetal]

I've only seen stripping in one firearm I own. That firearm is a S&W Model 25 in 45 Colt. The load is a RCBS 255 gr SWC over 9 grains of Unique. The revolver has an 8 3/8 inch barrel. I've recovered many slugs fired from it in very good condition and there have been times when there was only a fingernail click of lead ridge left between the rifling grooves on it....BUT THE DARN THINGS STILL SHOT MORE THE ACCURATE. It amazed me. 44man knows how that revolver shoots because he asked me to do a 100 yard target for him. Little off topic here, but the revolver has a .452 groove and the cylinder throats are .456. I shoot bullets, and those good groups, using bullets sized to .452. Yesh I have shot bullets sized .456 and over and believe it or NOT the accuracy wasn't as good as the .452 ones. One reason I don't subscribe to all the "theories" on fitting the cylinder throats. Don't get me wrong, I wouldn't expect a revolver that has smaller cylinder throats them the barrel groove diameter, to shoot good. But the other ways around...hmmmmm.... mine does.

Next time I revcover one of those bullets I'll post the picture. I've since remelted the ones I've had.

Joe

[felix]

That is true, Joe. Hardness of the boolit comes into play here. I have a 45 with the same dimensions, and it exhibits the very same thing with WW air cooled. Water drop those suckers, and all bets are off. ... felix

[StarMetal]

That is true, Joe. Hardness of the boolit comes into play here. I have a 45 with the same dimensions, and it exhibits the very same thing with WW air cooled. Water drop those suckers, and all bets are off. ... felix

Well Felix I hate to say this...throw my Smith into a big box full of various degree of hardness lead bullet, various brands of jacketed, and various powders.....and it will shoot good groups. This is by far one of the most accurate revolvers I've ever owned in my life. It shoots jacketed and lead bullets to about the same impact as long as they are about the same weights too. I've even shot hollow base conicals meant for the 1858 Remington cap n ball out of it...which those were pure lead. I've shot pure lead and every alloy inbetween that and linotype and it shoots good. I give up trying to find a bullet style in lead it doesn't like. I got more then lucky with this gun. I bought it in Tulsa, Ok when I lived there.

Joe

[Whitespider]

And then as we continue to push faster, the only logical conclusion is that the bullet begins to fail farther and farther up the slug which would make it look like it occurred in the bore when it was really external if you understand what I mean.

Yes, I think I know what you mean.
As the bullet exits the muzzle, less and less of the bullets bearing surface is “gripped” by the rifling, which could allow the base of the bullet (or possibly more, maybe up to half way) to “strip” to some degree. That sounds plausible, if the bullet is still under enough force and acceleration at exit. But even that wouldn’t change the rotational speed of the bullet enough to make any meaningful difference in performance.

Let’s say the base of the bullet did “strip” in such a manner, enough to be seen as widening of the engraving at the base by the naked eye, say .005 inch. At 1600 FPS, from a 1:12 barrel, the bullet would now be spinning at 95,520 RPM, verses 96,000 RPM for the bullet that didn’t “strip” at the base. Or, it would be spinning at the same rate as a bullet launched at 1592 FPS without “stripping”, just the shot to shot velocity variances would be greater than that. Even if it “stripped” enough to widen the engraving at the base by .010 inch it wouldn’t be as significant as shot to shot velocity variances (with most loads). The rate of spin is directly proportional to exit velocity, once the bullet clears the muzzle the there can be no increase of rotational speed; laws of physics again.

I will agree that it could (if it indeed does happen) be enough to affect a “clean” exit from the muzzle, and contribute to instability. But it does nothing to support your conclusion that a higher RPM results in deeper, straight line penetration. All of your test bullets, at the 1600 FPS level (or any velocity level) were spinning at the same relative-to-velocity rate, the RPM had nothing to do with penetration, or lack of it. The only conclusion I glean from your test(s) is that a stronger alloy withstands higher velocity and rotational forces when used with a 160-grain, .30 caliber, GC bullet during the first 50-yards of flight; beyond 50-yards is still an unknown (they may well “go to sleep” and hit at a better point-forward attitude beyond 50-yards), just as other bullets and diameters are still an unknown.

[leftiye]

However to give leftiye some credit he is correct in that deformation of the cast bullet is "the culprit". The centrafugal force of the RPMs is just what causes the "culprit" to go bad. If we can control the deformation of the bullet during accelleration then we can bump the RPM threshold upwards. Larry Gibson

Larry, If'n y'all had said that a couple of years ago, there would have been no dis agreement. Actually you did, but I couldn't get you to admit it, or repeat it. While y'ere worrying about rpms, why don'cha worry a little about the deflection of unstable or deformed boolits by the air?

[StarMetal]

Yes, I think I know what you mean.
As the bullet exits the muzzle, less and less of the bullets bearing surface is “gripped” by the rifling, which could allow the base of the bullet (or possibly more, maybe up to half way) to “strip” to some degree. That sounds plausible, if the bullet is still under enough force and acceleration at exit. But even that wouldn’t change the rotational speed of the bullet enough to make any meaningful difference in performance.

Let’s say the base of the bullet did “strip” in such a manner, enough to be seen as widening of the engraving at the base by the naked eye, say .005 inch. At 1600 FPS, from a 1:12 barrel, the bullet would now be spinning at 95,520 RPM, verses 96,000 RPM for the bullet that didn’t “strip” at the base. Or, it would be spinning at the same rate as a bullet launched at 1592 FPS without “stripping”, just the shot to shot velocity variances would be greater than that. Even if it “stripped” enough to widen the engraving at the base by .010 inch it wouldn’t be as significant as shot to shot velocity variances (with most loads). The rate of spin is directly proportional to exit velocity, once the bullet clears the muzzle the there can be no increase of rotational speed; laws of physics again.

I will agree that it could (if it indeed does happen) be enough to affect a “clean” exit from the muzzle, and contribute to instability. But it does nothing to support your conclusion that a higher RPM results in deeper, straight line penetration. All of your test bullets, at the 1600 FPS level (or any velocity level) were spinning at the same relative-to-velocity rate, the RPM had nothing to do with penetration, or lack of it. The only conclusion I glean from your test(s) is that a stronger alloy withstands higher velocity and rotational forces when used with a 160-grain, .30 caliber, GC bullet during the first 50-yards of flight; beyond 50-yards is still an unknown (they may well “go to sleep” and hit at a better point-forward attitude beyond 50-yards), just as other bullets and diameters are still an unknown.

This brings up a conversation I had with Bass via phone. I have firing slug from the 8x56R rifle I use to own. The slug has a raised ridge on the force side of the rifling groove. I'm talking a ridge higher then the diameter of the bullet. How could this be? Well I told Bass, and he probably knew it, that it had to happen as the bullet was leaving the muzzle, spinning raised that edge on the bullet as it passed the crown. We agreed it on it. The bullet being confined in the bore couldn't get a raised ridge on it.

Joe

[leftiye]

I jest gotta say it. This has been the absolutely best thread I've seen (maybe forever). Lots of good opinions. Lots of good information from member's experiences. Probly the best discussion of internal deformations of boolits ever. Also of how these deformations culminate at launch in instability and/or deflection.

[Larry Gibson]

Larry, If'n y'all had said that a couple of years ago, there would have been no dis agreement. Actually you did, but I couldn't get you to admit it, or repeat it. While y'ere worrying about rpms, why don'cha worry a little about the deflection of unstable or deformed boolits by the air?

Maybe I did say that a couple years ago and you just didn't notice;-) The deflection caused by the bullet being unstable is a separate issue and i believe i have addressed it on threads of a topic other than the stability of cast bullets. The issue with stability is what causes the initial abnormal flight of the bullet. In the cases most often under discussion it is the adverse affect of high RPM above the RPM threshold of any given load.

Of course the bullet is always meeting with air resistance from the time it is fired still in the chamber/barrel. How well it deals with that also will affect the flight path of the bullet. I attempted to note this by accurately measuring the BCs and reported such in my original post on the RPM threshold. I believe it was you and 3 others who gave me such a ration of **** that I quit posting the results. From other posts on other threads you have made I could have agreed and provided valid test data to back up your points. Since you argued so heavily against my being able to measure anything I didn't think you’d want the information. Perhaps that is all water under the bridge now and perhaps you are interested in the information. I shall then, when a topic comes up, provides some factual information regarding the deflection of " unstable or deformed boolits by the air."

Larry Gibson

[Larry Gibson]

Starmetal

I had a S&W M25 .45 ACP with a 6.5" barrel that did the same thing with soft cast 200 gr SWCs. The same load with the same bullet would not do it when fired in a M1911. With the same bullet cast harder there was only the usual "skidding" in the front shoulder of the SWCs when fired with the same load in the same M25. I attribute the "skipping" as happening in the forcing cone/leade area of the barrel due to the long cylinder throat jump and the shallow rifling of M25 revolvers. I do not believe it happened neither up the barrel nor on exit as there would have been "skidding" marks on the last part of the rifling and there wasn't. BTW; the load with that 200 gr SWC was 7.5 gr of Unique and it ran at 1025 fps from the M1911 and 975 fps the M25. Heavy Keith bullet loads, also with Unique, exhibited the same "skid" marks on the front driving bad but neither on the body nor the rear driving bands.

With regards to your accuracy with .452 bullets in the larger cylinder throats, I also find pretty much the same thing not only with .45 cylinders but with most any other revolver. With rare exception I find that if cast bullets of a 12-18 BHN are more than .002" over barrel groove diameter then accuracy actually decreases. I know this is heresy these days but if you have a bullet over that .002" just to fit the cylinder throat then accuracy will only be so so at best. As an example I have for years shot many a 240-250 gr SWC .44 bullets in .44 Specials and Magnums sized at .429 with as good accuracy as I or a Ransom rest could produce. Most often the cylinder throats were .431 to .432". When switching to "as cast" or sizing the bullets to .430-.432" no measureable increase in accuracy was found.

Now I will admit to having a couple of SAA with grossly oversize cylinder throats (.456-.457") where a .454-.456 bullet shot better in them with their .452" barrels than .452 sized cast bullets. I will say here though that accuracy only improved to the point I could call it "consistent" with the larger bullets vs the smaller ones which still was a far cry from where it should have been. I most always find that shooting a cast bullet larger than .003 over groove depth to be harmful to accuracy whether from rifle or handgun.

Just my observations Joe

Larry Gibson

[StarMetal]

Starmetal

I had a S&W M25 .45 ACP with a 6.5" barrel that did the same thing with soft cast 200 gr SWCs. The same load with the same bullet would not do it when fired in a M1911. With the same bullet cast harder there was only the usual "skidding" in the front shoulder of the SWCs when fired with the same load in the same M25. I attribute the "skipping" as happening in the forcing cone/leade area of the barrel due to the long cylinder throat jump and the shallow rifling of M25 revolvers. I do not believe it happened neither up the barrel nor on exit as there would have been "skidding" marks on the last part of the rifling and there wasn't. BTW; the load with that 200 gr SWC was 7.5 gr of Unique and it ran at 1025 fps from the M1911 and 975 fps the M25. Heavy Keith bullet loads, also with Unique, exhibited the same "skid" marks on the front driving bad but neither on the body nor the rear driving bands.

With regards to your accuracy with .452 bullets in the larger cylinder throats, I also find pretty much the same thing not only with .45 cylinders but with most any other revolver. With rare exception I find that if cast bullets of a 12-18 BHN are more than .002" over barrel groove diameter then accuracy actually decreases. I know this is heresy these days but if you have a bullet over that .002" just to fit the cylinder throat then accuracy will only be so so at best. As an example I have for years shot many a 240-250 gr SWC .44 bullets in .44 Specials and Magnums sized at .429 with as good accuracy as I or a Ransom rest could produce. Most often the cylinder throats were .431 to .432". When switching to "as cast" or sizing the bullets to .430-.432" no measureable increase in accuracy was found.

Now I will admit to having a couple of SAA with grossly oversize cylinder throats (.456-.457") where a .454-.456 bullet shot better in them with their .452" barrels than .452 sized cast bullets. I will say here though that accuracy only improved to the point I could call it "consistent" with the larger bullets vs the smaller ones which still was a far cry from where it should have been. I most always find that shooting a cast bullet larger than .003 over groove depth to be harmful to accuracy whether from rifle or handgun.

Just my observations Joe

Larry Gibson

Larry,

If I recall my recovered bullets they showed rifling skipping even on the base. I believe the skip was even fore and aft. Aye Aye Sir, see that Navy lingo in there???

I'll check see if I might have saved one, if now I'll see if I can shoot into something soft and catch another.

You're right about those puppies having shallow rifling. No ways near like there other calibers. Makes me think they went with the 45acp model first and then threw in the 45 Colt...anyone know?

Joe

[rbuck351]

Larry Assuming no stripping, what imbalances occur in the barrel to a naked bullet that don't happen to the pp bullet?

[Larry Gibson]

Larry Assuming no stripping, what imbalances occur in the barrel to a naked bullet that don't happen to the pp bullet?

I'm sure one of the PP boys could explain it a whole lot better than I can and in much more detail. I'll just give you the short version. The bullet used in PPing for higher velocity is usually at least bore diameter if not a tudge larger. It is either designed without any grooves, has very small shallow groove or when a regular cast bullet of that calibe is sized down the grooves become vsmall and shallow. Next wrap a paper jacket from below the base to where the ogive begins around it and size it so it is groove diameter or maybe a thou or two larger. That is your basic PP'd bullet. Again I've probably left out a few things but this is the short version.

What we end up with is a solid bullet with minimal grooves that are filled up with the solid paper jacket. The solid paper jacket, during accelleration supports the solid bullet and prevents set back, nose sloughing, collapse of lube grooves, uneven obturation of the bullet base and probably smaller cunks of the bullet breaking off the edges of the driving bands of harder alloys as they do in regular cast bullets with large deep lube grooves.

The PP along with all of the above also insulates the lead bullet from the friction of lead and lube on steel at high compression and friction. That's basically it in a nutshell. Again perhaps one of the PPing boys would care to elucidate.

Larry Gibson

[looseprojectile]

Bass is full of spin.
In his first post he says that velocity increased and spin decreased. BS.
In his post #46 he said that none of the boolits in the test skidded.
Just what is he trying to say? I have always tried to find the "sweet spot". I have loaded and fired dozens thousands of .357 magnum cartridges in a Ruger flattop and will testify that the faster they were launched the more accurate they were. When working up any load, over or under spinning a boolit has never happened to me. None that made any difference, anyway.
Felix and Bass both say we need to be able to measure the RPM of a fired boolit. Paraphrasing here. Not so. Accuracy and boolits can be destroyed by tipping the can too much, though.
If you can measure the velocity and know the twist you know the rotational speed [RPM] of the boolit, empirically. Absoutely. [Without a doubt, Uh huh.]
Now I don't know if a paradigm shift can be applied to boolits but I ain't buying any of this poo poo.
Oh, and it has been proven that slow heavy boolits with a large meplat penetrate much more in animals than high velocity expanding bullets. You takes your choice a bullet that might expand somewhere in the animal, or on the surface, or a boolit that goes through. It has also been said that if the boolit goes all the way through it is wasting energy. I like my boolits to have enough energy to waste some. Accuracy is right up there also. Help, I seem to be stuck in the mud.
Life is good

[felix]

LP, if for any reason you are going to measure forward velocity, why not also circumference velocity? If accuracy at a very specific range is the objective, then you need to know neither. ... felix

[looseprojectile]

Felix, I just need to know the approximate velocity of my rifle so I can get an approximate maximum point blank range. That is how I have always set up my hunting guns. BPCR guns have an uninspiring trajectory and are another wonder to deal with concerning sight settings. Unless you know the range and sight settings a BPCR is a short range thing for me as in hunting in brush.
And youre right I don't need to know most of the stuff I have learned in my life but some of this stuff is hard to forget.:drinks:

Life is good

[44man]

Slow elk and 44man

regarding bullets blowing up; Take two Hornady bullets, the standard .224 55 gr SP and the .224 55 gr SX which are identical all except for one thing. The jacket of the SX bullet is much thinner. Now load them to the same velocity in a 7-9" twist .223 to 3200 fps or in a 22-250 with 14" twist to 2600+ fps and see what happens. The standard Hornady 55 gr bullet will shoot nice littl groups. The 55 SX will do poorly because many of the bullets will disintegrate in flight before they reach a 100 yard target. The difference is the thinner jacket of the 55 gr SX is not capable of holding the bullet together and withstanding the extreme centrafugal force of the very high RPMs. Fun to watch though!

Larry Gibson
That is why I loved the Swift! The faster twist allowed me to shoot the 60 gr for super long range with accuracy great enough to head shoot most chucks to 600 yards. Imagine what an SX bullet would do! [smilie=1: Have to wear a mask to keep from breathing the dust. :bigsmyl2:
I never liked the 22-250 twist because lighter bullets were needed and I did not like them for long range. They were fine with 50-55 gr and even the 55 was borderline.
For lighter bullets for closer range I used my .222. What a great gun that was.
They thought I was nuts when I chuck hunted, I always had 3 guns in the car, my .44 flat top for out to 100 yd's, the .222 for up to 300 and the Swift for beyond 300.
I taught myself to take a perfect 3' pace and would only be a foot off on a measured range. My longest shot on a crow with the Swift was 410 yards but I could not hit them over 300 with the .222, never figured drop close enough and I would cut the branch under their feet. :Fire: Fun to see them fall until they could get wings moving.

[44man]

303guy

Did you recover any of the bullets that hit the target side ways? If so they do you have a picture of them? If not then how do you know the "stripped in the bore"? Key holing is not an indicator of "stripping".

Larry Gibson
I have from a 30-30. The boolit was accurate enough to hit a nickel at 100 yards as long as I used the gas check but would hit a 50 yard target sideways if I shot it without a check. I found some of them and although flat on one side, the other side had perfect rifling marks. I attribute the trouble to being a match to the rifling with the check and a mismatch with it off. Maybe a reduced load would have fixed it but I was shooting IHMSA.
As far as skidding, that's what I call it when a boolit "skids" a little before taking the rifling.
Stripping would be for the length of the barrel, common with say a .38 with wad cutters after the rifling packed with lead so there was no grip to a boolit. It would strip without spinning for beans all the way out.
I can see one "stripping" if the wrong alloy is shot too fast in a rifle but do not think it happens under most conditions. Most boolits will form to the bore with pressure, a case where some upset is good as long as the lead is not so soft it loses grip and shears.
I have no answer but it sounds good. :drinks:

[Whitespider]

Larry Assuming no stripping, what imbalances occur in the barrel to a naked bullet that don't happen to the pp bullet?

...The bullet used in PPing for higher velocity is usually at least bore diameter if not a tudge larger. ... perhaps one of the PPing boys would care to elucidate.

Actually, the proper paper patch bullet should be bore (not groove) diameter at the base, tapering forward slightly to a smaller diameter. Two layers of paper (usually .002 thick) are wrapped around the bullet (building the bullet diameter by approximately .008), making the patched bullet groove diameter at the base tapering forward to something less than bore diameter. By design, this is so the paper gently engages the rifling without tearing; usually only the rear part of the patched bullet is fully gripped by the rifling while the patched forward part is sort of a bore-rider. Normally, the “paper” used for patching has a high cotton content (up to 100% cotton) which gives it extremely high compression characteristics. The paper extends past the base and is twisted up and/or pressed into a concave hollow base, if available.

A paper patched bullet is a paper-jacketed bullet. The paper, wrapped very tightly, is strong, very strong and supports the lead, minimizing or eliminating slump, on its trip down the barrel. The paper protects the base and sides from gas cutting, something that will definitely cause balance problems. No lead ever touches steel; the lead is protected from the direct effects of friction (i.e. tearing, gouging, melting, etc.). Higher velocity is produce at lower pressure because the paper, which is normally lubed, slides easier against steel than lead, creating far less friction and heat. The paper is a lousy conductor of heat, so very little heat is transferred to the lead; the hotter the surface of the lead the weaker it becomes. Because of the compressive nature of the paper, very little lead is displaced by the rifling lands, sort of like a sabot.

All this adds up to a bullet that has suffered far less stress and exits the barrel in very good condition, almost pristine when compared to a bare lead bullet. The paper patched bullet is cleaner, smoother, rounder, and stronger; better balanced and in much better condition to withstand the centrifugal forces during flight.

[45 2.1]

Actually, the proper paper patch bullet should be bore (not groove) diameter at the base, tapering forward slightly to a smaller diameter. Two layers of paper (usually .002 thick) are wrapped around the bullet (building the bullet diameter by approximately .008), making the patched bullet groove diameter at the base tapering forward to something less than bore diameter. By design, this is so the paper gently engages the rifling without tearing; usually only the rear part of the patched bullet is fully gripped by the rifling while the patched forward part is sort of a bore-rider. Normally, the “paper” used for patching has a high cotton content (up to 100% cotton) which gives it extremely high compression characteristics. The paper extends past the base and is twisted up and/or pressed into a concave hollow base, if available.

A paper patched bullet is a paper-jacketed bullet. The paper, wrapped very tightly, is strong, very strong and supports the lead, minimizing or eliminating slump, on its trip down the barrel. The paper protects the base and sides from gas cutting, something that will definitely cause balance problems. No lead ever touches steel; the lead is protected from the direct effects of friction (i.e. tearing, gouging, melting, etc.). Higher velocity is produce at lower pressure because the paper, which is normally lubed, slides easier against steel than lead, creating far less friction and heat. The paper is a lousy conductor of heat, so very little heat is transferred to the lead; the hotter the surface of the lead the weaker it becomes. Because of the compressive nature of the paper, very little lead is displaced by the rifling lands, sort of like a sabot.

All this adds up to a bullet that has suffered far less stress and exits the barrel in very good condition, almost pristine when compared to a bare lead bullet. The paper patched bullet is cleaner, smoother, rounder, and stronger; better balanced and in much better condition to withstand the centrifugal forces during flight.

You can here all sorts of things. I would read some other things before I believed some of what is above.

[XWrench3]

look, i do not like to burst anyones bubble, or hamper scientific advances in any way, shape, or form. but i think there are some flaws with your expeiment. in my simple non-scientific mind, the only way to "prove" your theory would be to use barrels and projectiles of the same caliber with different twist rates where you are not varying velocity to vary the twist rate. if the bullet penetrates deeper at the exact same velocity with one twist rate than another, then you may be on to something. but in order to prove your theory, you can only vary one thing at one time. when you increase velocity to increase the twist (rpm) you are varying two things at one time. in my simple little mind, a faster projectile will always penetrate deeper than a slower one IF both bullets deform the same amount (or not at all). i can see where some rotation could provide for deeper penetration by helping to work through muscle. but unless there is an extreem difference, it would seem like it would not make that much difference. lets face it, even a slow moving bullet from a slow twist rate gun is spinning pretty fast. the drilling action would hardly be influenced by the "threads" cut into the bullet by the rifling. now, if the nose of the bullet had a screw thread cast into it, sort of like a wood screw, using a FAST twist rate may increase the penetration to a measureable amount. most 30 caliber rifle have a 1 in 10 twist rate, plus, (and i may be wrong on this one) i would think that the most of us are not shooting 30 caliber lead projectiles. i am sure there are a bunch of us out there, but i do not think it is the most popular LEAD bullet caliber. of course, that has no bearing on your experiment, other than you will have a harder time finding barrels of different twist rates. .22 caliber rifles have the widest range that i know of, ( 1 in 7 to 1 in 14") but may be of little interest to most shooters. i personally think you need to rethink your experiment, adjust and set some new parameters, and try again. not many great things have been learned and proven on the first try. so do not quit, just keep trying. and work out all the bugs.

[Whitespider]

You can here all sorts of things. I would read some other things before I believed some of what is above.

By all means... :wink: ...do your own investigation, draw your own conclusions... I would!

[Larry Gibson]

XWrench3

Your very scientific thought process belays your claim of [B]"[in my simple non-scientific mind"/B].....well put post!

Larry Gibson

[Larry Gibson]

Quote:
Originally Posted by 45 2.1

"You can here all sorts of things. I would read some other things before I believed some of what is above."

Whitespider

Don't sweat the small stuff considering there was only criticism there and no explanation of his own as is his usual style. Would be much better in these discussions if he could add something to them instead of always just critisizing. Your explanation was pretty good. I particularly liked your summation which was much better than mine;

"All this adds up to a bullet that has suffered far less stress and exits the barrel in very good condition, almost pristine when compared to a bare lead bullet. The paper patched bullet is cleaner, smoother, rounder, and stronger; better balanced and in much better condition to withstand the centrifugal forces during flight."

I believe that to be the case exactly, well put.

Larry Gibson

[45 2.1]

Larry, everyone knows what your up to, so stuff a sock in it.

[leftiye]

Originally Posted by Larry Gibson
Joe

All that is correct with one caveat, actually there are 3 area's of stabilization generally recognised; minimally stable, stable and over stablized. Larry Gibson

Disagree, it is stabiized or it is unstable to some degree.

[StarMetal]

That is why I loved the Swift! The faster twist allowed me to shoot the 60 gr for super long range with accuracy great enough to head shoot most chucks to 600 yards. Imagine what an SX bullet would do! [smilie=1: Have to wear a mask to keep from breathing the dust. :bigsmyl2:
I never liked the 22-250 twist because lighter bullets were needed and I did not like them for long range. They were fine with 50-55 gr and even the 55 was borderline.
For lighter bullets for closer range I used my .222. What a great gun that was.
They thought I was nuts when I chuck hunted, I always had 3 guns in the car, my .44 flat top for out to 100 yd's, the .222 for up to 300 and the Swift for beyond 300.
I taught myself to take a perfect 3' pace and would only be a foot off on a measured range. My longest shot on a crow with the Swift was 410 yards but I could not hit them over 300 with the .222, never figured drop close enough and I would cut the branch under their feet. :Fire: Fun to see them fall until they could get wings moving.

44man,

My longest shot on a prairie dog with my Colt HBAR using a crummy Vietnam 55 gr FMJ (this was a reload using those bullets) was 375 yards resting the rifle over a fallen tree. I'd say a crow and that particular dog were close in size. When I was shooting ground hogs back in PA my friend really couldn't out do me with his Ruger Varminter in 22-250, I was using a Winchester Varminter in 223. That use to really make him angry knowing the 22-250 really was bigger cartridge that should have shot farther. He was a good shot too so that wasn't the problem.

Joe

[leftiye]

Originally Posted by 45 2.1
You can here all sorts of things. I would read some other things before I believed some of what is above.

By all means... ...do your own investigation, draw your own conclusions... I would Whitespider

W..... The investigation has already been done, and it seems your "correct way" is just "another way." You might want to confer with Pdawg shooter, he's been patching for 30 years. I'm aware that some do it your way, but you can't sniff at 3000 fps with 1 moa.

[Whitespider]

W..... The investigation has already been done, and it seems your "correct way" is just "another way."
Well leftiye, I never used the term "correct way"...
...I used terms like, "should be", "usually", "sort of", "normally" and "if available"...
...my reply was not intended to be an instructional; I was simply responding to (or adding to) a question posed by rbuck351 and answered by Larry Gibson.


...but you can't sniff at 3000 fps with 1 moa.
I agree... I 100% agree.

[44man]

44man,

My longest shot on a prairie dog with my Colt HBAR using a crummy Vietnam 55 gr FMJ (this was a reload using those bullets) was 375 yards resting the rifle over a fallen tree. I'd say a crow and that particular dog were close in size. When I was shooting ground hogs back in PA my friend really couldn't out do me with his Ruger Varminter in 22-250, I was using a Winchester Varminter in 223. That use to really make him angry knowing the 22-250 really was bigger cartridge that should have shot farther. He was a good shot too so that wasn't the problem.

Joe
I agree. I never lost accuracy with the .222, it is just I never shot it enough past 300 yards to learn the drop. I just loved the Swift too much and knew every inch of drop from 300 to 600. It was taped to my Balvar 24 scope and each distance could be dialed in, in a second. The .222 had a Weaver 10X on it.
The 22-250 never impressed me because it never seemed any better then the .222's or the .223. Wrong bullets for really long range. Now stepping up to the .244 was another story and it out did the .243 in spades. The .243 was a deer rifle from the start but lighter bullets for varmints was where the .244 shined.
How I miss the old days! :drinks:

[NHlever]

Looseprojectile, don't beat around the bush, tell us what you really think! :D :D :D I tend to agree with you.

Hmm, overstabilized? Perhaps that means that the bullet, or boolit is being spun too fast for the quality, or strength of the bullet? I knew a guy that had an 8" twist 22-250 years ago. He sure got some quick expansion, but he needed to shoot very good bullets to maintain group size. I had a very accurate .250 Savage once that would shoot smaller groups at longer range than it did up close with boattail bullets. I think it took a while for them to "go to sleep", perhaps that is the sort of thing you are talking about?

[StarMetal]

Looseprojectile, don't beat around the bush, tell us what you really think! :D :D :D I tend to agree with you.

Hmm, overstabilized? Perhaps that means that the bullet, or boolit is being spun too fast for the quality, or strength of the bullet? I knew a guy that had an 8" twist 22-250 years ago. He sure got some quick expansion, but he needed to shoot very good bullets to maintain group size. I had a very accurate .250 Savage once that would shoot smaller groups at longer range than it did up close with boattail bullets. I think it took a while for them to "go to sleep", perhaps that is the sort of thing you are talking about?

Your post made me remember something I've thought of before. If the bullet is darn near perfect..or the heck of it...let's say it IS pefect (talking jacketed here) is there such a thing as over stabilization then?? While you're thinking about posting a reply think about the things that rotate at high speed that aren't bullets...such as a dentist drill, or special race car engines that run up in the 6 digit rpm range. I think that last one is good because you're not just dealing with one rotating mast. I certainly know and agree if a bullet isn't perfect spinning it really fast will destroy it's accuracy potential. Just how perfect are today's target jacketed bullets?

Joe

[StarMetal]

I agree. I never lost accuracy with the .222, it is just I never shot it enough past 300 yards to learn the drop. I just loved the Swift too much and knew every inch of drop from 300 to 600. It was taped to my Balvar 24 scope and each distance could be dialed in, in a second. The .222 had a Weaver 10X on it.
The 22-250 never impressed me because it never seemed any better then the .222's or the .223. Wrong bullets for really long range. Now stepping up to the .244 was another story and it out did the .243 in spades. The .243 was a deer rifle from the start but lighter bullets for varmints was where the .244 shined.
How I miss the old days! :drinks:

Don't get me wrong, I think the 22-250 is a great round. I'm not one for what I describe as the big boomers per caliber. Your 220 Swift and 22-250 in the 22 caliber class are examples. I prefer the 222 or 223..heck even the 22 Hornet. Savage will give you a 22-250 with a faster twist...9 I believe.

Joe

[Whitespider]

If the bullet is darn near perfect..or the heck of it...let's say it IS pefect (talking jacketed here) is there such a thing as over stabilization then??

Yes, YES, YES!!! That’s just the point I’ve been trying to make since my first reply in this thread; any projectile can be over-stabilized. It just takes a lot more RPM to over-stabilize a “perfect” projectile, but it can still be over-stabilized.

When a bullet is over-stabilized it begins to deform from centrifugal force, more so at points that are weaker or damaged, which creates an unbalanced situation and causes wobble. If spun fast enough, the mythical “perfect” bullet, which would not have weaker or damaged areas, would deform equally around it’s total circumference, remaining in balance but misshapen. If spun ever faster and faster, over-stabilized more and more, it would reach a point where the centrifugal force would cause the “perfect” bullet to fly apart. But, as we all know, there is no such thing as perfect.

The less “perfect” the bullet (as in weaker and/or more damaged, unbalanced, etc.), the less centrifugal force it is able to withstand and remain stabilized. But, a certain amount of spin is required to stabilize any bullet and if the bullet is weak enough, or damaged enough, it will go directly from an under-stabilized condition to an over-stabilized condition. In other word, it can not withstand the minimum amount of spin (centrifugal force) needed to overcome under-stabilization.

Even if the projectile was made “perfectly” of hard diamond and spun fast enough, it would deform and eventually fly apart... because it was over-stabilized.

[StarMetal]

Yes, YES, YES!!! That’s just the point I’ve been trying to make since my first reply in this thread; any projectile can be over-stabilized. It just takes a lot more RPM to over-stabilize a “perfect” projectile, but it can still be over-stabilized.

When a bullet is over-stabilized it begins to deform from centrifugal force, more so at points that are weaker or damaged, which creates an unbalanced situation and causes wobble. If spun fast enough, the mythical “perfect” bullet, which would not have weaker or damaged areas, would deform equally around it’s total circumference, remaining in balance but misshapen. If spun ever faster and faster, over-stabilized more and more, it would reach a point where the centrifugal force would cause the “perfect” bullet to fly apart. But, as we all know, there is no such thing as perfect.

The less “perfect” the bullet (as in weaker and/or more damaged, unbalanced, etc.), the less centrifugal force it is able to withstand and remain stabilized. But, a certain amount of spin is required to stabilize any bullet and if the bullet is weak enough, or damaged enough, it will go directly from an under-stabilized condition to an over-stabilized condition. In other word, it can not withstand the minimum amount of spin (centrifugal force) needed to overcome under-stabilization.

Even if the projectile was made “perfectly” of hard diamond and spun fast enough, it would deform and eventually fly apart... because it was over-stabilized.

But I'm talking a perfect bullet fired at very high rpm that doesn't self destruct it. Take a solid copper bullet like a Barnes. Within it's rpm limit, if the bullet is perfect, would there then be a more perfect rpm range for accuracy and would that range necessarily be in the lower rpm range?

Joe

[Willbird]

The word strip must have consistent meaning here. Strip means the projectile goes through an interrupting change in twist force, however small, which is not commensurate with the acceleration of the projectile at that instant. ... felix

This explains the reasoning behind "seasoning" a barrel, and why some barrels will print to point of aim on the first shot, and others won't. This is also why some lubes will shoot "screamers" with a certain load and others won't. ... felix

For the RPM when the bullet exits the muzzle NOT to be proportional to the fps velocity then "reswaging" or whatever would have to be taking place within the last few inches of rifle barrel, and the gas pressure at that point is not high enough to accomplish plastic deformation of the bullet, nor is there a great deal of acceleration going on a that point either.

Has anybody ever successfully measured how long a bullet keeps rotating as it penetrates a medium such as water ?

Dr. Harold Vaughn glued rare earth disk magnets into slits in the noses of bullets, then fired them through the center of a wound copper coil and looked at the results on a oscilloscope, he told of this in his book "Rifle Accuracy Facts"

It is quite ludicrous to measure penetration and try to theorize what bullet rpm was from the penetration, there are many factors going on such as cavitation that would completely skew any simplistic look at the results.

Varmint Al did some hoop strength analysis of bullet jackets, to try to understand why bullets fail at too high an RPM, and he arrived at the fact that the damage done to the bullet by the rifling was what allowed the bullets to fail when fired in a very fast twist, a bullet launched from a sabot would have none of that damage, and could reach almost twice the rpm of one damaged by rifling.

Shilen makes 30 caliber barrels in 8,10,12,13,14,15,and 17 twist

[NHlever]

Your post made me remember something I've thought of before. If the bullet is darn near perfect..or the heck of it...let's say it IS pefect (talking jacketed here) is there such a thing as over stabilization then?? While you're thinking about posting a reply think about the things that rotate at high speed that aren't bullets...such as a dentist drill, or special race car engines that run up in the 6 digit rpm range. I think that last one is good because you're not just dealing with one rotating mast. I certainly know and agree if a bullet isn't perfect spinning it really fast will destroy it's accuracy potential. Just how perfect are today's target jacketed bullets?

Joe

Today's target bullets are very good indeed as is witnessed by the tiny groups that benchresters get. No, I don't think there is such a thing as overstabilization when we are talking about bullets, or boolits. Once a bullet is stabilized there isn't much past that. Now, if you spin it faster than is needed for that to happen you may find that it deflects less easily ( think of a football pass when a player just ticks, or touches the ball in flight. If the ball is spinning slowly it gets deflected, if it is spinning quite fast, sometimes it wobbles a bit, and then settles down again. ) Will it penetrate on a more straight path......... well that kind of depends on expansion, but I would put my money on a fast twist with solids. Will it drift more in the direction of rotation during it's flight.............. hmm, don't know. I do know that the vernier tang sights on the old black powder guns were mounted at a slight angle to compensate for bullet drift at longer ranges.

[NHlever]

Yes, YES, YES!!! That’s just the point I’ve been trying to make since my first reply in this thread; any projectile can be over-stabilized. It just takes a lot more RPM to over-stabilize a “perfect” projectile, but it can still be over-stabilized.

When a bullet is over-stabilized it begins to deform from centrifugal force, more so at points that are weaker or damaged, which creates an unbalanced situation and causes wobble. If spun fast enough, the mythical “perfect” bullet, which would not have weaker or damaged areas, would deform equally around it’s total circumference, remaining in balance but misshapen. If spun ever faster and faster, over-stabilized more and more, it would reach a point where the centrifugal force would cause the “perfect” bullet to fly apart. But, as we all know, there is no such thing as perfect.

The less “perfect” the bullet (as in weaker and/or more damaged, unbalanced, etc.), the less centrifugal force it is able to withstand and remain stabilized. But, a certain amount of spin is required to stabilize any bullet and if the bullet is weak enough, or damaged enough, it will go directly from an under-stabilized condition to an over-stabilized condition. In other word, it can not withstand the minimum amount of spin (centrifugal force) needed to overcome under-stabilization.

Even if the projectile was made “perfectly” of hard diamond and spun fast enough, it would deform and eventually fly apart... because it was over-stabilized.

Ah, but that bullet is not overstabilized, it is just being spun too fast for it's quality, or strength. When a bullet is stabilized it is spinning perfectly true (in an ideal world) That can happen through a wide range of rpm. Below that acceptable rpm it is not stabilized, and beyond that range it becomes unstable because of defects in the bullet, or it's strength. A bullet is stable, or not stable.

[NHlever]

Hey folks we are getting pretty serious about all this. There is a cool video at Barnsbullets.com that shows the whole thing perfectly...... kinda skinny rifling marks on the bullet though.

[StarMetal]

Maybe some of you will appreciate this slow motion video of a bullet going through gelatin. Most of you have only seen the gelatin shot real time or a picture of after it was shot. I think this will open many eyes.
http://www.collegehumor.com/video:1787993

Joe

[Willbird]

The whole "over stable" thing is a misnomer. Either it is stable or it is not. Flaws in the bullet cause inaccuracy, BUT the spin on the bullet means the deviation from the theoretical line of flight causes an error that is radial from that theoretical line of flight. Fire enough shots and you will create a perfect circle. The higher the rpm of the bullet the larger that circle will be, but it is an issue of magnitude.....the error does not go away when the bullet is just barely stable...it is just reduced in magnitude.

Bullets do lose some BC the higher the rpm is cranked because the nose of the bullet moves to one side and up due to gyroscopic precession. Again an issue of magnitude, the effect is always there, but it increases as bullet rpm increases.

With bullets that will shoot in the .2's with a 1/14 twist I would expect typically to see that group open up to the high .3's if you used twice the twist needed for the job. Not 1/4moa with a 1/14 and 4 moa with a 1/7 which some people have taken it to mean. With very good bullets most shooters have tons of other factors going on(wind for one) that far outshadow any inaccuracy caused by having more twist than is needed for the bullet being used.

I'd far rather shoot a group for $$ with a 1/8 twist 6-284 loaded with 75 grain bullets and some wind flags out there over say 300 yards than try to do the same with a 1/12 twist and NO feedback on wind intensity and direction.

Cavitation in fluids is a lot more important factor affecting penetration than rifling twist.

Bill

[NHlever]

Good input, and good thoughts.

[Whitespider]

The whole "over stable" thing is a misnomer. Either it is stable or it is not.
You and NHlever are confusing meanings of terms; yes “over stable” is a misnomer, but “over-stabilized” is not. When speaking in ballistic terminology the word “stabilized” refers to the physical spinning of the bullet, a bullet that has not been “stabilized” is not spinning at all and will tumble from the moment it exits the muzzle. A bullet that is spinning too slowly may not be 100% “stable”, yet it is flying in a relative point-forward attitude and is in fact correctly termed “under-stabilized”. Conversely, a bullet spinning fast enough to deform and/or eventually destruct may not be 100% “stable”, yet it is flying in a relative point-forward attitude (at least until it destructs) and is in fact correctly termed “over-stabilized”.


Bullets do lose some BC the higher the rpm is cranked because the nose of the bullet moves to one side and up due to gyroscopic precession. Again an issue of magnitude, the effect is always there, but it increases as bullet rpm increases.
First, gyroscopic precession probably does not apply to this discussion; the effect is not always there, it only manifests itself after the bullet has reached the apex of its trajectory and begins the downward curve. At this point, high pressure builds under the nose of the bullet, trying to force the nose up. The gyroscopic force of the spinning bullet resists the upward force, which causes the nose to tilt slightly to the right or left (depends on direction of spin). Now the high pressure is to one side of the nose, the gyroscopic force again resists, causing the nose to tilt down, then to the other side, then up, then to the side, etc., etc., etc. The bullet nose rotates (relatively slowly) around a tiny, central high pressure zone. Gyroscopic precession is actually beneficial, it allows the point of the bullet to assume a point-down attitude during the downward curve of the trajectory; without gyroscopic precession the gyroscopic force of the spinning bullet would hold the nose in an upward position during the downward trajectory curve, virtually destroying the ballistic coefficient.

But as I said, it probably does not apply to this discussion; at only 50-yards, and depending on the sight height of the rifle Bass was using, I doubt the bullets had begun their downward curve.


AND FINALLY...
I quote from Jim Carmichel...
”No shooting subject is more likely to make one sound like an expert, and at the same time prove him a fool, than a discussion of rifling twist.”

[Larry Gibson]

I do not claim to be an Expert but let me tell you what I have found by actually measuring BCs. BCs are the measurement of bullets efficiency in flight. But first let's discuss "stabilization". There are indeed degrees of stabilization a bullet can be minimally stabilized, stabilized and over stabilized. As mentioned a non-stabilized bullet is one that is no longer flying point forward and is tumbling. Now then those are accepted realities in the science of ballistics.

The degree of stabilization, given a “perfect” bullet or at least vary good ones, is based on RPM and is governed by the twist given an equal velocity. I have found this to be the case when measuring BCs of 155, 168 and 175 gr MK bullets in 10, 12 and 14” twist .308W rifles. I also have found the very same circumstance with 55, 68 and 75 gr match bullets in 7, 8, 9 and 12” twist .223 rifles. In the tests all velocities were consistent within normal velocity variations for a given load. Each one of those particular bullets have a particular twist with which it’s BC will consistently be the highest. This higher BC reflects the most efficient flight and thus the best degree of stabilization. If the BC was lower in a faster twist (higher RPM) this gives evidence of over stabilization. Conversely if the BC was also lower in a slower twist (less RPM) then that is evidence of under stabilization.

Let’s take the case of the 175 MK in the .308W; in this case the 12” twist barrel invariably produces the higher BC. Will the faster 10 and 14” twist have less intrinsic accuracy because of their lower BCs than the 12” twist? Not necessarily so as each bullet has a spectrum of RPM where it will become stabilized and stay that way during its flight. Actually the difference in BCs is small but none the less there is a difference. We probably would not be able to see an intrinsic difference in accuracy between the 3 different twists. However what we will see if we shoot at longer ranges is the bullet that has the higher BC will fly through conditions such as the wind better. Also as the trajectory starts down the over stabilized bullets angle of incidence will tent to stay as it was in the angle of departure. The under stabilized bullet may be more susceptible to precessions which can adverse affect it’s accuracy. However the stabilized bullet with the highest BC is more like to nose over and follow a more accurate flight path. Thus on a practical level a given bullet will be the accurate out of a twist that will give it the highest BC vs the BCs produced by either faster or slower twists. This has been well documented by many long range HP shooters who play with different twists seeking the best and most consistent accuracy at long range. I believe Tubb has written several articles on this in a couple publications of recent.

Larry Gibson

[303Guy]

...
What about barrel time?
A jacketed shot real slow is in the bore longer and might get hotter.
I have picked up thousands of bullets and never seen the heat discoloration on the metal 303guy shows....That was my conclusion too. Take a look.

http://i388.photobucket.com/albums/oo327/303Guy/MVC-580F_edited.jpg
Full power loads and no heating of the jacket!

On the question of 'overstabilization' (I haven't read all the posts yet), 'overstabilization' would be the theoretical stabilization that prevents a bullet from aligning its spin axis with its line of flight. i.e. Travelling nose high at the end of its trajectory.

But what if the the heating was present due to high core pressure (as in upset) due to high pressure in the bore. Would the jacket become loose after exit while it was still hot and expanded, resulting in poor accuracy? That's my theory, anyway.

[StarMetal]

That was my conclusion too. Take a look.

http://i388.photobucket.com/albums/oo327/303Guy/MVC-580F_edited.jpg
Full power loads and no heating of the jacket!

On the question of 'overstabilization' (I haven't read all the posts yet), 'overstabilization' would be the theoretical stabilization that prevents a bullet from aligning its spin axis with its line of flight. i.e. Travelling nose high at the end of its trajectory.

But what if the the heating was present due to high core pressure (as in upset) due to high pressure in the bore. Would the jacket become loose after exit while it was still hot and expanded, resulting in poor accuracy? That's my theory, anyway.

You're not talking about a lot of upset in jacketed because most of them in ideal conditions are groove size. The most done to them is the rifling engraving and that's not enough to loosen that core. If what you think were true there would be many inaccurate bullets and that's just not the case.

Joe

[Willbird]

I do know that 357 maximum bullets immediately recovered completely undamaged from fiberfill are too hot to hold.

Whether or not the RPM exceeds the yield strength or ultimate tensile strength of the bullet has nothing to do with stability. The two things are not related. As I said "over stable" is a poor description and a misnomer. The RPM at which the bullets fails mechanically is a thing unto itself, and other than in extreme cases is not often encountered in bullets that are even close to being correct for the job at hand. Who has ever blown up a conservative 30 caliber cast bullet with too much RPM ?

The bit about the bullet not flying point forward is not strictly an effect present after the bullet starts on the downward portion of the parabola. It has been discussed over and over again in Precision Shooting articles that a bullet flies with it's nose slightly up and to one side, increasing rpm increase this effect.

Bill

[44man]

Some great reading here! :Fire:
I never got too involved when I varmint hunted but learned very quick that a rifle that shot super tiny groups at 100 usually does not maintain accuracy at long range. A combination that shoots very small groups at 400 or farther usually does not group at 100.
Selecting a twist and bullet has to be done for the range to be shot and I never worked with a bullet at 100 in a rifle I was using at 400 to 600. In fact I could miss a chuck at 100 very easily yet hit one in the head at 500.
This usually meant a faster twist for me. Much easier to develop a long range load plus the bullets needed bucked conditions better.
So without the math, it matches what a lot of you are explaining.
You can see the effect if you watch a 240 gr bullet shot from a S&W 29 as the bullet spirals around the flight path shot to 200 meters and if you could still see the bullet near 200, you would see the spiral get reduced. This spiral stops by going to a heavier bullet which reduces velocity and spin.
I call the 240 "over stabilized", a 250 to 265 would be stable but if you shoot the heavier bullet slow with little charges of fast powder, they would be "under stabilized" and long range accuracy suffers. This would be the same in the S&W if you go to a 300 gr because the gun can't handle a load high enough to make it stable.
Not being able to watch a rifle bullet only leaves us to see what it does on paper.
Anyway, to search for the smallest groups at closer ranges with a long range rifle will leave you disappointed when extending the range. I will take a faster twist every time unless I just shot close ranges.
So while you discuss a 10", 12" or 14" twist you must consider at what distance each is best at and which bullet matches the twist for the distance.
There is perfesser gun, perfesser deer and perfesser target! :mrgreen:

[NHlever]

"You and NHlever are confusing meanings of terms; yes “over stable” is a misnomer, but “over-stabilized” is not. When speaking in ballistic terminology the word “stabilized” refers to the physical spinning of the bullet, a bullet that has not been “stabilized” is not spinning at all and will tumble from the moment it exits the muzzle. A bullet that is spinning too slowly may not be 100% “stable”, yet it is flying in a relative point-forward attitude and is in fact correctly termed “under-stabilized”. Conversely, a bullet spinning fast enough to deform and/or eventually destruct may not be 100% “stable”, yet it is flying in a relative point-forward attitude (at least until it destructs) and is in fact correctly termed “over-stabilized"

I stand corrected! I was confusing the term stable with the word stabilization, and didn't understand the effect that it has on a bullet's forward flight path. I did some further research to help me understand better, and found this illustration:
http://www.nennstiel-ruprecht.de/bullfly/fig15.htm
and this: http://www.fulton-armory.com/fly/stab.htm
Thanks guys for being patient enough to help teach an old guy new things.

[StarMetal]

I was surprised that nobody said a thing about the slow motion video of a bullet going through gelatin, so I will. It's clearly evident that there is rotational energy. The higher the rpm the higher that energy has to be. This is also evident in a rotating tire on a went road throw off a rooster tail of water.

44man you logic seems to hold some water. I remember when Weatherby came out with his high dollar target or tactical model rifle. The gun writer first sighted it in at 100 yards to get it on paper. He was very disappointed with the 100 yard groups as they were pretty big. He was again very surprised when he shot it at 300 yards and it printed smaller groups. Sounds like what you experienced.

Joe

[44man]

I was surprised that nobody said a thing about the slow motion video of a bullet going through gelatin, so I will. It's clearly evident that there is rotational energy. The higher the rpm the higher that energy has to be. This is also evident in a rotating tire on a went road throw off a rooster tail of water.

44man you logic seems to hold some water. I remember when Weatherby came out with his high dollar target or tactical model rifle. The gun writer first sighted it in at 100 yards to get it on paper. He was very disappointed with the 100 yard groups as they were pretty big. He was again very surprised when he shot it at 300 yards and it printed smaller groups. Sounds like what you experienced.

Joe
My .220 Swift would never break 1" at 100 yards no matter what I did. It drove me nuts until I decided to just get sight settings for all the ranges. I got hammered for this [smilie=1: but I shot several groups at 350 yards that measured 1/4". Not all the time of course but average groups were very small and always better then I could get at 100.
I guess I should explain my meaning for over stabilized. It is spinning too fast to go to sleep at close range but will do so downrange at some point. Accuracy is decent at close range but not the best.
Under stabilized will give good accuracy at close range but downrange at some point the bullet will wander off course and widen groups beyond usefulness, even if wind, etc is not present.
There is a very tight relationship between forward velocity and spin rate. You just can't change one without the effect of the other changing things.
You can see that with a bullet not spinning fast enough to start and even though spin does not degrade as fast as velocity, as soon as velocity drops so does stability. Spin the bullet up faster and even though velocity drops at range, the spin can still keep the bullet on line and stable. I can't say spin reduces the effect of a bullet dropping subsonic or not because a lot of the guns I was shooting most likely never dropped out subsonic at the distances I shot. It very well might help because of the problems I see with my BPCR that does not spin a boolit fast enough with a high enough starting velocity. The boolit can be seen on a straight path until downrange at some point where it will then head off in different directions. I am beginning to think a BP 45-70 should have a 1 in 14" twist. 1 in 18" and 1 in 20" work better with smokeless.
How I wish I could afford to prove it! :(

[44man]

I can't comment on the spin having a larger effect on killing an animal, it might, I don't know. If the wound channel is the same diameter with less spin I don't see it matters. But the question of a large secondary channel that collapses after boolit passage, leaving a small primary has a small killing effect. Only an increase of the primary wound channel will kill faster. So spinning up a large secondary from spin of the bullet might mean nothing.
Anyway after doing a necropsy on many hundreds of deer I never seen twisted lungs and a slow round ball from a .54 muzzle loader does as much damage as a .300, in fact deer die faster, a lot faster, then too powerful a rifle.
Not counting spine or nervous system hits where a difference will not be seen.

[outdoorfan]

I remember reading on another forum that there was an individual who had over time tested different twist barrels (3 different ones, I think) in his 300 Weatherby. He shot multiple coyotes with all three, and his observation was that the faster twist always left bigger exit holes. FWIW.

[44man]

I remember reading on another forum that there was an individual who had over time tested different twist barrels (3 different ones, I think) in his 300 Weatherby. He shot multiple coyotes with all three, and his observation was that the faster twist always left bigger exit holes. FWIW.
That is a very small animal. How can he determine what spin does in large game?
When I shot crows to 410 yards, only wings came out of the tree, the body was gone, yet I can't tell anyone that it was spin. Head shooting a chuck left a flap that fell back in place so the animal looked normal. Lift the nose and most inside was gone but I never seen spiral damage to what was left.
The higher spin might just have made the bullets tumble on contact.
I do not believe those kinds of tests that quantify a reason without looking at the whole spectrum.

[StarMetal]

44man,

What is the twist of your 220 Swift. Looking in an old Speer manual there is a page of common twists for various calibers used by the major manufacturers and they list the Swift with a 14, which I thought it was, and the 22-250's at 12. Now we know today this has changes, as the 22-250 can be had with a 9 twist. You quoted your Swift as having a faster twist then the 22-250. Are you confusing a larger number, such as 14, a faster twist then the 22-250's 12 twist which we see is a lower number?

Joe

[44man]

44man,

What is the twist of your 220 Swift. Looking in an old Speer manual there is a page of common twists for various calibers used by the major manufacturers and they list the Swift with a 14, which I thought it was, and the 22-250's at 12. Now we know today this has changes, as the 22-250 can be had with a 9 twist. You quoted your Swift as having a faster twist then the 22-250. Are you confusing a larger number, such as 14, a faster twist then the 22-250's 12 twist which we see is a lower number?

Joe
Mine was a pre 64 model 70 Winchester with a 1 in 10" twist. Heavy stainless barrel.

[StarMetal]

Mine was a pre 64 model 70 Winchester with a 1 in 10" twist. Heavy stainless barrel.

Thanks Jim, that explains it.

Joe

[Whitespider]

My .220 Swift would never break 1" at 100 yards no matter what I did. It drove me nuts until I decided to just get sight settings for all the ranges. I got hammered for this but I shot several groups at 350 yards that measured 1/4". Not all the time of course but average groups were very small and always better then I could get at 100.
I guess I should explain my meaning for over stabilized. It is spinning too fast to go to sleep at close range but will do so downrange at some point....
I am beginning to think a BP 45-70 should have a 1 in 14" twist. 1 in 18" and 1 in 20" work better with smokeless.
How I wish I could afford to prove it!

44man,
There is a flaw in your thinking, which is easy to do as a shooter. You’re thinking in terms of distance (i.e. 100-yard, 350-yards, etc.), and as a shooter/hunter you need to think distance at times. But all the things that affect a bullets flight (i.e. going to sleep, drift, trajectory, etc.) are not determined by distance, the key is TIME, time of flight.

If your Swift bullet was over-stabilized I doubt it would’ve have printed such tiny groups farther down range. It takes time for the bullet to “go to sleep[”, pretty close to the same amount of time for all bullets; but a bullet fired from the Swift at near 4000 FPS just travels farther down range during that time. It wasn’t that the Swift bullet was over-stabilized; the problem was that your 100-yard target wasn’t allowing enough time for the bullet to “go to sleep[”. Whereas a cast bullet fired at 1600 FPS may have more than enough time for the bullet to “go to sleep[” before it reaches 50-yards down range.

It’s the same with wind drift (or anything else concerned with the bullets flight). It isn’t the distance of travel that determines how much the bullet will drift. Rather it’s how much time the wind is allowed to force its effects on the bullet that determines the amount of drift. Faster bullet, less time in flight, less wind drift.

If you want to fully grasp the principles of ballistics, you have to start thinking like a ballistician; it is important, no imperative that you stop thinking in segments of distance and begin thinking in segments of time. Actually, that’s been the cause of error in of many the opinions and assumptions in this thread; the author was basing them on observations of distance rather than observations of time.

[felix]

All center fire 22's except for the Hornet, were stock 14 twist until the military interfered. Yes, time is the only variable that is not a variable and everything must have that variable as a basis constant. There is only one Alpha and Omega. ... felix

[StarMetal]

44man,
There is a flaw in your thinking, which is easy to do as a shooter. You’re thinking in terms of distance (i.e. 100-yard, 350-yards, etc.), and as a shooter/hunter you need to think distance at times. But all the things that affect a bullets flight (i.e. going to sleep, drift, trajectory, etc.) are not determined by distance, the key is TIME, time of flight.

If your Swift bullet was over-stabilized I doubt it would’ve have printed such tiny groups farther down range. It takes time for the bullet to “go to sleep[”, pretty close to the same amount of time for all bullets; but a bullet fired from the Swift at near 4000 FPS just travels farther down range during that time. It wasn’t that the Swift bullet was over-stabilized; the problem was that your 100-yard target wasn’t allowing enough time for the bullet to “go to sleep[”. Whereas a cast bullet fired at 1600 FPS may have more than enough time for the bullet to “go to sleep[” before it reaches 50-yards down range.

It’s the same with wind drift (or anything else concerned with the bullets flight). It isn’t the distance of travel that determines how much the bullet will drift. Rather it’s how much time the wind is allowed to force its effects on the bullet that determines the amount of drift. Faster bullet, less time in flight, less wind drift.

If you want to fully grasp the principles of ballistics, you have to start thinking like a ballistician; it is important, no imperative that you stop thinking in segments of distance and begin thinking in segments of time. Actually, that’s been the cause of error in of many the opinions and assumptions in this thread; the author was basing them on observations of distance rather than observations of time.

Yet 44man figured that at 350 yards the bullet had the correct amount of "TIME" in flight to go to sleep. If he doesn't change that load and it's fired in the same weather conditions it's all going to stay the same. He didn't need to study ballistics to find that out. Sounds like he didn't shoo the Swift at close distances and used a smaller 22 centerfire cartridge.

Joe

[Whitespider]

StarMetal,
You totally miss the whole point of my post. I wasn’t making the point that a fella’ needs to study ballistics to shoot well, or to developed an accurate load, or to learn a what range his rifle shoots best.
44man summed up his post with this...

I am beginning to think a BP 45-70 should have a 1 in 14" twist. 1 in 18" and 1 in 20" work better with smokeless.
How I wish I could afford to prove it!
...because he made the assumption (or came to the conclusion) that the Swift bullet was over-stabilized and a 1:18 or 1:20 twist would work better.

Well, I can tell you that those slow twists will not work worth diddly with anything but the absolutely lightest .22 caliber bullets (maybe). If 44man would have been thinking in segments of time he would never have come to that conclusion; he would not only know the Swift shoots better at ranges beyond 100-yards, he would also know WHY!.

I guess some people don’t care about the “(why)” of things, they just accept it for what it is. That’s not me, it drives me bonkers until I learn the “(why)”, and I believe it keeps me from making poor decisions (like wasting money building a Swift with a 1:20 twist).

[StarMetal]

StarMetal,
You totally miss the whole point of my post. I wasn’t making the point that a fella’ needs to study ballistics to shoot well, or to developed an accurate load, or to learn a what range his rifle shoots best.
44man summed up his post with this...

...because he made the assumption (or came to the conclusion) that the Swift bullet was over-stabilized and a 1:18 or 1:20 twist would work better.

Well, I can tell you that those slow twists will not work worth diddly with anything but the absolutely lightest .22 caliber bullets (maybe). If 44man would have been thinking in segments of time he would never have come to that conclusion; he would not only know the Swift shoots better at ranges beyond 100-yards, he would also know WHY!.

I guess some people don’t care about the “(why)” of things, they just accept it for what it is. That’s not me, it drives me bonkers until I learn the “(why)”, and I believe it keeps me from making poor decisions (like wasting money building a Swift with a 1:20 twist).

White,

I didn't miss your point, don't think 44man did either. I learned long ago the longer the bullet is in flight the more time wind has to work on it.

Joe

[44man]

StarMetal,
You totally miss the whole point of my post. I wasn’t making the point that a fella’ needs to study ballistics to shoot well, or to developed an accurate load, or to learn a what range his rifle shoots best.
44man summed up his post with this...

...because he made the assumption (or came to the conclusion) that the Swift bullet was over-stabilized and a 1:18 or 1:20 twist would work better.

Well, I can tell you that those slow twists will not work worth diddly with anything but the absolutely lightest .22 caliber bullets (maybe). If 44man would have been thinking in segments of time he would never have come to that conclusion; he would not only know the Swift shoots better at ranges beyond 100-yards, he would also know WHY!.

I guess some people don’t care about the “(why)” of things, they just accept it for what it is. That’s not me, it drives me bonkers until I learn the “(why)”, and I believe it keeps me from making poor decisions (like wasting money building a Swift with a 1:20 twist).
Nope, you missed what I said. I said the 45-70 BPCR might work better with a FASTER twist for long range because BP does not have enough starting velocity and smokeless will work with a 1 in 18" or a 1 in 20" in strong, modern actions. NOT THE .22.
Please go back and read it again. I was discussing a .45-70.
I am a firm believer in a faster twist for long range and you can slow it down for close range so the bullet goes to sleep sooner.

[Whitespider]

Ahhhhhh........ I did misunderstand. :roll:
My apologies, just ignore post #126.

[44man]

Ahhhhhh........ I did misunderstand. :roll:
My apologies, just ignore post #126.
No problem, it is mostly my fault for mixing things in. I get hard to understand most times. Old age ya know! :coffee:

[felix]

Nah, don't forget, post 126 is correct in using the time construct, not distance. ... felix

[44man]

That is true, He actually said what I was saying about bullets going to sleep and agreed with me. Whitespider knows what he is talking about. Time is correct but time is also distance traveled depending on velocity. So time to sleep is also a different distance for each twist rate and velocity.
We can't separate spin and velocity nor can we separate time and distance.
It makes me think of my friend Pete, trying to shoot groups with his .50 BMG at 100 and 200 yards! [smilie=b:

[felix]

That brings to mind about the Big Bertha experiment during WWI shooting for Paris from the German border. They did not hit Paris because they did not, could not, figure the time of travel to where Paris really was at a specific time. ... felix

[StarMetal]

Nah, don't forget, post 126 is correct in using the time construct, not distance. ... felix

The time is correct, but does a military sniper have the times written on a piece of paper taped to his buttstock...or more modern, does the spotters range finder give the time to the target, or does it show the distance in yards/meters? I believe probably the distance, although technically time is the more precise, but the sniper uses distance....as the time is automatically figured in for his load and rifle. Simulated scenario: "Well spotter, what do you have?" Spotter "Well sir, it's .0216745 seconds to the target" Sniper "Hmmmm, let's see, that's 3 clicks up on elevation".

Joe

[felix]

Don't real (long range) snipers have pocket computers nowadays? If not, they are being shorted. GPS technology, as well as range finder integration, have been around for quite a few years. They installed that kind of computer on the local battlewagon (Wisconsin?) during VietNam days. That monster could hit a football field without fail, day or night in any kind of weather, on land and sea combined, 26 miles away. ... felix

[StarMetal]

Don't real (long range) snipers have pocket computers nowadays? If not, they are being shorted. GPS technology, as well as range finder integration, have been around for quite a few years. They installed that kind of computer on the local battlewagon (Wisconsin?) during VietNam days. That monster could hit a football field without fail, day or night in any kind of weather, on land and sea combined, 26 miles away. ... felix

Gosh Felix....you side stepped my question! You know they figure for distance, not time.

Joe

[outdoorfan]

Don't real (long range) snipers have pocket computers nowadays? If not, they are being shorted. GPS technology, as well as range finder integration, have been around for quite a few years.


Over on the Long Range Hunting forum, guys like Shawn Carlock have/use exactly that.

[Whitespider]

StarMetal, seriously, you've totally missed the point.
It has absolutely nothing to do with ranging the target, or how many elevation clicks on the scope it will take to hit said target. It has nothing to do with being a crack shot, or being good at duping the wind. It starts at a much deeper level than that. It has to do with comparisons, evaluations and the formulation of conclusions; it's a scientific, more objective way of looking at evidence and deciphering it while keeping the hype and myths from getting in your way, clouding your judgment. It's admitting that our eyes, as well as our hearts, can be easily deceived; that seeing is not always believing thing.

Knowledge is power my man....... knowledge is power.

[StarMetal]

StarMetal, seriously, you've totally missed the point.
It has absolutely nothing to do with ranging the target, or how many elevation clicks on the scope it will take to hit said target. It has nothing to do with being a crack shot, or being good at duping the wind. It starts at a much deeper level than that. It has to do with comparisons, evaluations and the formulation of conclusions; it's a scientific, more objective way of looking at evidence and deciphering it while keeping the hype and myths from getting in your way, clouding your judgment. It's admitting that our eyes, as well as our hearts, can be easily deceived; that seeing is not always believing thing.

Knowledge is power my man....... knowledge is power.

...oh..so I team of ballistic experts and scientist go with the sniper team (and serious groundhog hunters) and with sophisticated equipment, computors, and calculators...and after an analysis the sniper's scope is magically dialed in huh?

Please stop saying what you THINK I did or didn't get. You don't know and you don't know me.

Joe

[Whitespider]

It has nothing to do with snipers or groundhog hunting either. [smilie=1:

[StarMetal]

It has nothing to do with snipers or groundhog hunting either. [smilie=1:

See....but that is what I am talking about. You missed that point.:roll:

I never said what you talked of as being wrong. I know what you discussed is the reason those snipers and hog hunters can do what they do.

Joe

[Bret4207]

If your Swift bullet was over-stabilized I doubt it would’ve have printed such tiny groups farther down range. It takes time for the bullet to “go to sleep[”, pretty close to the same amount of time for all bullets; but a bullet fired from the Swift at near 4000 FPS just travels farther down range during that time. It wasn’t that the Swift bullet was over-stabilized; the problem was that your 100-yard target wasn’t allowing enough time for the bullet to “go to sleep[”. Whereas a cast bullet fired at 1600 FPS may have more than enough time for the bullet to “go to sleep[” before it reaches 50-yards down range.

It’s the same with wind drift (or anything else concerned with the bullets flight). It isn’t the distance of travel that determines how much the bullet will drift. Rather it’s how much time the wind is allowed to force its effects on the bullet that determines the amount of drift. Faster bullet, less time in flight, less wind drift.

If you want to fully grasp the principles of ballistics, you have to start thinking like a ballistician; it is important, no imperative that you stop thinking in segments of distance and begin thinking in segments of time. Actually, that’s been the cause of error in of many the opinions and assumptions in this thread; the author was basing them on observations of distance rather than observations of time.

That's interesting. I think that is the first time I've seen that thought presented in those terms, and I've read a lot of opinion on the subject. Thanks, I found that to be intriguing and a thought provoking post. :drinks:

[felix]

Bret, now that you picked up on that time parameter as being a major culprit, let's expand a little about keeping the boolit's direction in line (commensurate) with gravity. This is about the stability parameter as presented here. Yes, there are three generic states in reality, but we can take into practice only two, the boolit being either under or over stabilized, and never be stabilized except maybe for a fraction of the total flight time using a very well calculated twist for that boolit. Like we use a PID controller for making boolits, we can use one embedded into boolits making guided missles instead. ... felix

[Whitespider]

StarMetal,

I’m gonna’ apologize ahead of time for continuing to harp on this. It may very well be that you “get it”, but your comments continue to indicate that you do not really understand what I’m talking about. When I sight my deer rifle in, or take a shot at a deer, I’m not gonna get out my ballistic calculator and figure “time of flight” before making the shot. I know my rifle hits about an inch high at 100-yards, dead on at 200-yards, about 3 inches low at 300-yards and I need to “hold over” and into the wind beyond that. I don’t use “time of flight” to determine the required hold or sight settings; using yardage is still the fastest and most efficient method.

But let’s say I’m fine tuning a couple of loads. For the sake of argument, let’s say they’re both already highly accurate loads but I’m wanting to experiment with seating depth and squeeze that last tiny millimeter of accuracy from them. So I load rounds for both rifles, five different seating depths for each, and head to the shooting range. When I get there the wind is quartering from the right and into my face at 5 MPH. Now wind is never steady, let’s say it’s varying from 4 to 6 MPH, and because of the lay of the land it varies slightly in direction and speed at various spots down range; i.e. the amount of wind effect on the bullet is gonna’ vary from shot to shot. Now remember, I’m trying to eek that last tiny bit of accuracy from my loads, I’m gonna’ shoot groups and compare them to each other.

I set my targets up at 100-yards. The first rifle is my .22-250, shooting a streamlined jacketed bullet with a BC up around .300, at 3800 FPS. I’m not really concerned about the wind, that bullet is gonna get to the target so fast that a light quartering wind won’t skew my results enough to matter. Because it’s a quartering wind, it would be like a cross wind varying from 1 to 3 MPH; just shot to shot velocity differences will have more effect than the wind. I don’t have to know the exact “time of flight”, just knowing it will be way, way less than a .10 second is enough. I shoot my groups, compare targets and determine that X seating depth is better than the others... COOL!

Next I get out my .222, shooting a cast round nose with a BC down around .100, at 1700 FPS. Now I’m concerned about the wind. Again, I don’t need to know the exact “time of flight”, just knowing that it will be about three times as long, or may be even more, than the .22-250 is all I need to know. That’s a lot of time for the wind to force its affects on a bullet having a BC around .100, it would skew my results enough that my targets are meaningless (remember, I’m looking for that last tiny bit of accuracy). I need to reduce the “time of flight” by about two thirds if I if I want to get anything usable from this range session. If I’m thinking in yards, that would mean setting my targets at 33-yards (that’s two thirds less right). But I’m not thinking in yards, I’m thinking in time. That boolit, with its low BC is gonna’ traverse the first 33-yards a whole lot faster than it will traverse the last 33-yards. See, I’m thinking in segments, not segments of distance, but segments of time. I still don’t need to know the exact time, but a quick “guesstimate” tells me that setting my targets at 50 or 55-yards is gonna’ reduce "time of flight" by at least two thirds, may be even a bit more. It will be a lot easier to see, or measure, any improvement in accuracy at 50-yards than it would be at 30-yards.

It wasn’t that I needed to know exact "time of flight", get out my ballistic calculator, or even look at ballistic tables. It’s a thought process, a way of breaking down the bullets trajectory into segments that are more efficient and precise than distance.

[felix]

Very good, WS! ... felix

[44man]

Very good, WS! ... felix
Yep, the way it is but what you said has a LOT of meaning, that a boolit is perfectly stable for only a short length of it's flight. Time OR distance is different for each load for where that point is or how long, in time or distance the stability lasts.
I still have a hard time separating time and distance! Can't be done!
Whitespider says it because he is changing distance for velocity and time of flight but has a hard time saying it. [smilie=1:[smilie=1:
We have to stop thinking time to target and think time to either stability and instability and at what distance each is for every twist and load. The time is going to say how far. How far is at what time.
Lets take a bullet spinning slow and it is deadly accurate from 25 to 200 yards but loses accuracy beyond that. Does it matter how long flight time was? Up the spin without changing velocity and it is now accurate from 200 to 400 yards but not so good at 25 to 200 or after 400. Would not flight time be the same since the velocity is the same? But distance for stability changed!
Speed up the velocity the same for both twist rates, does this not just extend the distance of stability because in each case the bullet is spinning faster? Now the slow twist is accurate from 100 to 300 and the faster twist is accurate from 300 to 500.
Looks like distance of stability means more then time to stability or when it ends because we can't measure time while shooting but we can see what a bullet does at each distance.
If we measured time, we would also get distance traveled.
OUCH, I need a drink! :drinks:

[felix]

Also, very good, 44man! Distance versus time has always been the primary subject explaining the use of Calculus. It works because time has been defined as a consistent constraint, meaning that it never changes (in rate). So, the variable in our question becomes the distance (or volume, or anything OTHER than time). In that respect, you are correct in the measurement of distance as opposed to time. But, distance by definition becomes the quicksand in the analysis because it is the secondary element, and not the concrete primary. Again, there is no way we can get around it. And, for this reason I cannot fathom folks not believing in God, the Alpha and Omega, especially scientists, engineers, technicians. ... felix

[Whitespider]

Whitespider says it because he is changing distance for velocity and time of flight but has a hard time saying it.

Well, no, that’s not quite right (a least not in my above example).
I’m changing distance (to target) in order to make the most efficient use of time, as well as force time to work in my advantage, or at least to my lesser disadvantage.

[Willbird]

Actually if you look at wind drift figures what you said is not exactly true.....time of flight does not determine wind drift, and here is a way to illustrate that....

Go to this url

http://www.biggameinfo.com/index.aspx?page=%2fbalcalc.ascx

If you do the calculations here is what you will get

.308 bullet
.320 BC
3400 fps muzzle velocity
2004 fps at 500 yards
.577 time of flight
23.8 inches of wind drift at 500 yards


.308 bullet
.420 BC
3000 fps muzzle velocity
1986 fps at 500 yards
.616 time of flight
20.4 inches of wind drift at 500 yards


Note that the bullet with the higher BC has LESS wind drift even though it has a longer time of flight. The amount of velocity a bullet LOSES from muzzle to target is a large factor in wind drift, this effect is especially evident if you compare a bullet that is supersonic all the way to the target with one that is subsonic all the way to the target.

.308 bullet
.420 BC
1200 fps muzzle velocity
1045 fps at 200 yards
.539 time of flight
6.8 inches of wind drift at 200 yards

.308 bullet
.420 BC
1000 fps muzzle velocity
917 fps at 200 yards
.628 time of flight
4.9 inches of wind drift at 200 yards

Bill

[44man]

Actually if you look at wind drift figures what you said is not exactly true.....time of flight does not determine wind drift, and here is a way to illustrate that....

Go to this url

http://www.biggameinfo.com/index.aspx?page=%2fbalcalc.ascx

If you do the calculations here is what you will get

.308 bullet
.320 BC
3400 fps muzzle velocity
2004 fps at 500 yards
.577 time of flight
23.8 inches of wind drift at 500 yards


.308 bullet
.420 BC
3000 fps muzzle velocity
1986 fps at 500 yards
.616 time of flight
20.4 inches of wind drift at 500 yards


Note that the bullet with the higher BC has LESS wind drift even though it has a longer time of flight. The amount of velocity a bullet LOSES from muzzle to target is a large factor in wind drift, this effect is especially evident if you compare a bullet that is supersonic all the way to the target with one that is subsonic all the way to the target.

.308 bullet
.420 BC
1200 fps muzzle velocity
1045 fps at 200 yards
.539 time of flight
6.8 inches of wind drift at 200 yards

.308 bullet
.420 BC
1000 fps muzzle velocity
917 fps at 200 yards
.628 time of flight
4.9 inches of wind drift at 200 yards

Bill
That is very true but we have been leaving out the outside influences like wind and just thinking about stability from twist and velocity. The same bullet at the same velocity will have the same time but changing the spin can alter the distance of starting and ending stability. Changing velocity with the same twist will also alter the distance of each.
No matter what you do at the gun by changing twist, velocity and time of flight, you are going to change the distance where the bullet is most stable.
I do not care if my bullet is stable at .22376540001 in time from the muzzle, I want to know at what distance that is. I shoot yards and meters not parts of seconds. I just have not figured out how to pace distance that fast! :kidding:

[StarMetal]

StarMetal,

I’m gonna’ apologize ahead of time for continuing to harp on this. It may very well be that you “get it”, but your comments continue to indicate that you do not really understand what I’m talking about. When I sight my deer rifle in, or take a shot at a deer, I’m not gonna get out my ballistic calculator and figure “time of flight” before making the shot. I know my rifle hits about an inch high at 100-yards, dead on at 200-yards, about 3 inches low at 300-yards and I need to “hold over” and into the wind beyond that. I don’t use “time of flight” to determine the required hold or sight settings; using yardage is still the fastest and most efficient method.

But let’s say I’m fine tuning a couple of loads. For the sake of argument, let’s say they’re both already highly accurate loads but I’m wanting to experiment with seating depth and squeeze that last tiny millimeter of accuracy from them. So I load rounds for both rifles, five different seating depths for each, and head to the shooting range. When I get there the wind is quartering from the right and into my face at 5 MPH. Now wind is never steady, let’s say it’s varying from 4 to 6 MPH, and because of the lay of the land it varies slightly in direction and speed at various spots down range; i.e. the amount of wind effect on the bullet is gonna’ vary from shot to shot. Now remember, I’m trying to eek that last tiny bit of accuracy from my loads, I’m gonna’ shoot groups and compare them to each other.

I set my targets up at 100-yards. The first rifle is my .22-250, shooting a streamlined jacketed bullet with a BC up around .300, at 3800 FPS. I’m not really concerned about the wind, that bullet is gonna get to the target so fast that a light quartering wind won’t skew my results enough to matter. Because it’s a quartering wind, it would be like a cross wind varying from 1 to 3 MPH; just shot to shot velocity differences will have more effect than the wind. I don’t have to know the exact “time of flight”, just knowing it will be way, way less than a .10 second is enough. I shoot my groups, compare targets and determine that X seating depth is better than the others... COOL!

Next I get out my .222, shooting a cast round nose with a BC down around .100, at 1700 FPS. Now I’m concerned about the wind. Again, I don’t need to know the exact “time of flight”, just knowing that it will be about three times as long, or may be even more, than the .22-250 is all I need to know. That’s a lot of time for the wind to force its affects on a bullet having a BC around .100, it would skew my results enough that my targets are meaningless (remember, I’m looking for that last tiny bit of accuracy). I need to reduce the “time of flight” by about two thirds if I if I want to get anything usable from this range session. If I’m thinking in yards, that would mean setting my targets at 33-yards (that’s two thirds less right). But I’m not thinking in yards, I’m thinking in time. That boolit, with its low BC is gonna’ traverse the first 33-yards a whole lot faster than it will traverse the last 33-yards. See, I’m thinking in segments, not segments of distance, but segments of time. I still don’t need to know the exact time, but a quick “guesstimate” tells me that setting my targets at 50 or 55-yards is gonna’ reduce "time of flight" by at least two thirds, may be even a bit more. It will be a lot easier to see, or measure, any improvement in accuracy at 50-yards than it would be at 30-yards.

It wasn’t that I needed to know exact "time of flight", get out my ballistic calculator, or even look at ballistic tables. It’s a thought process, a way of breaking down the bullets trajectory into segments that are more efficient and precise than distance.

Your first paragraph, that's what I was getting at. I was also being a little smartly pants about it. Like I said most hunters or whatever, shoot by distance not thinking about the time of flight. Now the varminters do know that the time flight is important in windy conditions.

I know all what your talking up. I've used the time of flight that Lyman puts in the ballistics section for their cast bullets. Some of the "long" times are amazing.

I like 44man's gist on all this and want to bring up again what he said and that is you adjusted the time of flight by adjusting the distance. Wow! How many hunters do you know that would LOVE to bring that big trophy animal closer to them??????

Me, I'm not your average bear happy with low velocity cast shooting. I like to work at the higher velocities and have been quite successful in that area. A question was asked why do you shoot cast. Most it was the economics. Not me, I took pleasure in making my own bullets and I wanted them to replace my jacketed loads, by that I mean velocity. Yes I do shoot slow target loads for some situations. To put it another way if I'd got into making my own jacketed bullet I'd never looked at cast bullets. As it way cast came first and I stuck with it.

Joe

[Willbird]

StarMetal,


I set my targets up at 100-yards. The first rifle is my .22-250, shooting a streamlined jacketed bullet with a BC up around .300, at 3800 FPS. I’m not really concerned about the wind, that bullet is gonna get to the target so fast that a light quartering wind won’t skew my results enough to matter. Because it’s a quartering wind, it would be like a cross wind varying from 1 to 3 MPH; just shot to shot velocity differences will have more effect than the wind. I don’t have to know the exact “time of flight”, just knowing it will be way, way less than a .10 second is enough. I shoot my groups, compare targets and determine that X seating depth is better than the others... COOL!

.

I'm not sure exactly how accurate your 22-250 is, but with that bullet at that velocity at 100 yards a 3mph wind will have a .2" effect on bullet point of impact. My 22-250AI shoots in the .2's at 100 yards, for good results I cannot ignore a .2" factor in bullet POI.

Bill

[Whitespider]

Actually if you look at wind drift figures what you said is not exactly true.....time of flight does not determine wind drift, and here is a way to illustrate that....

Willbird,
That’s just silliness. Your first example compares two bullets of different BC, the equivalent of tossing a football and a basketball. A higher BC means the bullet will be less affected by all the variables, except time (as Felix put it, time passes at a constant rate) which is a non-varying variable. Time is still the constant; a higher BC is just less affected during that time.

Your second example just illustrates something that has been known by the ballistic sciences for a long, long time, and is still not fully understood (research is ongoing). As a bullet passes into and out of transonic (speed of sound) flight, all the affects of variables (except time) are greatly multiplied, because the bullet loses velocity at a much higher rate during that time period. The speed of sound varies somewhere between 1000 and 1200 FPS depending on altitude and atmospheric conditions (the standard number is 1125 FPS at sea level, in dry air, at 68 degrees). Again, time is the only constant, non-varying variable.

These are classic examples of judgment being clouded by the hype and myths I was talking about in an earlier post. It’s just like your belief that the bullet flies constantly nose up and to one side (which, by the way, is impossible if the bullet is under the effects of gyroscopic precession), a myth that dates back to the days of the buffalo hunter and used to explain why a bullet tends to drift in the direction of spin, noticeable at long range (again, a conclusion based on distance, rather than time). That myth was debunked many years ago by the ballistic sciences, yet many shooters and gun writers cling to it, or just repeat what those before them stated or believed.


I'm not sure exactly how accurate your 22-250 is, but with that bullet at that velocity at 100 yards a 3mph wind will have a .2" effect on bullet point of impact. ...for good results I cannot ignore a .2" factor in bullet POI.

Oh c’mon man, it was just an example, heck I don’t even own a .22-250, or a .222 for that matter. But even so, I have an answer for you. You are correct if I’m just gonna’ use a single data set (i.e. a single group from each seating depth), but I wouldn’t because a single data set is worthless even in zero wind. But if I use a multiple data set (i.e. several groups from each seating depth) the .2 wind drift (the maximum for any single shot, remember the wind is varying 1 to 3 MPH) is not enough to skew the results over the average when the comparison is made. Yes, statistically that means that any wind can be ignored if enough data sets are used, but I’m not gonna’ shoot 50 or 60 5-round groups just so I can ignore a 10 MPH cross wind, I’ll wait for a calmer day.

[Bret4207]

Whoa!!! Hey Mods, keep the sticky button ready for this one! I'm totally confused, but there's a spark of comprehension glowing in the back of my brain.

[1Shirt]

Just an observation on an old mans part here: Threads like this tend to make me wonder why I started reading beyond the first response in the first place. I shoot and hunt for the enjoyment of it, and not for the science and math.
1Shirt!:coffee:

[Willbird]

Willbird,
That’s just silliness. Your first example compares two bullets of different BC, the equivalent of tossing a football and a basketball. A higher BC means the bullet will be less affected by all the variables, except time (as Felix put it, time passes at a constant rate) which is a non-varying variable. Time is still the constant; a higher BC is just less affected during that time.




I used two different BC's on PURPOSE, to illustrate my point, I raised the muzzle velocity of the lower BC bullet until the impact velocity was equal to the bullet with the higher BC. Thus the bullet with the lower BC had a much shorter time of flight, equal impact velocity, and yet was affected by wind MORE.

Please explain to me why a bullet with a higher BC (this typically will be a bullet with a larger cross section for the wind to work on) that spends more time in flight, is LESS effected by wind drift ?? Making a statement like "bullets with a higher BC will be affected by all factors less except time" is completely mind boggling. Especially when the earlier statement was "wind drift is determined by time of flight".

There is no hype, myths, smoke, or mirrors involved.

As to bullets in flight and gyroscopic precession, when an object that is functioning as a gyroscope has an outside force applied it moves in a direction 90 degrees from where the force was applied............correct ?? So we have a 3000 fps wind pressing on the nose of the bullet.....right ?? And we have a smaller wind created by the fall of the projectile created by gravity.......right ?? So with what we know about gyroscopes.......how will the bullet react to these two forces ?? By precessing............right ?? How will that precession allow the bullet to fly perfectly point forward ??

There are TWO curves in the trajectory, one is caused by the rotation of the bullet, the other is caused by Coriolis force. The direction of rifling twist determines of the two will work against each other, or with each other.

Ballistics have been unchanged since the Eniac computer was built, one thing it was used for was to create ballistics tables that are still used today.

Bill

[felix]

Eniac was built just for naval ballistics and nothing else. It just so happened that other folks saw the light and made use of that "technology" which evolved by default into what computers are built for now. The prevalent application for digital computers nowadays is for data capture and/or presentation rather than for data manipulation.

BC concepts and relevant calculations result in an attempt to simulate a point of view. It is far too difficult to emulate the real thing because of all the variable dependencies. That is why folks take readings at the beginning of flight and at the end of flight as a minimum to derive the most appropriate BC value.

Bill, the emphasis would be placed upon the target when using emulation, rather than using simulation techniques. Dan's program at MM would generate the boolit and gun required when given ALL of the environmental constraints. ... felix

[StarMetal]

Everything changes except time...well that is until you push that bullet to the speed of light...then time changes too! [smilie=1: Yeah Yeah I know, don't even say it.

Joe

[felix]

No, Joe, time does not change. Speed is based upon distance. Remember the "quicksand" statement above? Don't they measure particle speed by photographic means (historical) when the particles are traveling faster than the speed of light? ... felix

[StarMetal]

No, Joe, time does not change. Speed is based upon distance. Remember the "quicksand" statement above? Don't they measure particle speed by photographic means (historical) when the particles are traveling faster than the speed of light? ... felix

You need to study Einsteins theories. Time does change. Thus the reason space men going to a very distance place can be gone only say 3 yrs, but upon return to earth the earth has passed hundred's of years. Another place it changes is inside a black hole. Another place it changes is a worm hole. This they are very interested in because it is indeed time travel.

Joe

[StarMetal]

So you're saying this isn't true huh Felix?:

How Time Slows Down
As the speed of any object increases, its properties, as measured by an observer at rest, change. Its mass increases, its length in the direction of travel decreases and time slows down. At ordinary Earthbound speeds, even those of a jet plane, the changes are infinitesimal.
At very high speeds, however, the changes become extremely important. An astronaut travelling at 90 per cent of the speed of light, for instance, would not feel any different from his twin on Earth. But the mass of his spacecraft would be more than double, its length would be less than half and a clock on board would take an hour to record 25 minutes because time had slowed - and he would therefore be ageing at less than half the speed of his brother.
At the speed of light, the mass of his spacecraft would become infinite, its length would shrink to nothing and time aboard it would slow to a complete stop. Since this is impossible, nothing, other than light, can travel as fast as, nor faster than light.

[felix]

Three years in whose time? ... felix

[felix]

No, Joe, it is location, location, location (the integration of distance over a FIXED time). ... felix

[StarMetal]

Unhuh, you keep believing that Felix. I'll stick with Albert.

Joe

[felix]

Albert DID NOT SAY THAT! ... felix

[StarMetal]

Albert DID NOT SAY THAT! ... felix

I didn't say he said that, but who was it...Bode?

Joe

[felix]

This should help you, Joe. If not, perhaps I can remember enough to help you through it. ... felix

Faster-than-light observations and experiments
Main article: Faster-than-light
The blue glow in this "swimming pool" nuclear reactor is Čerenkov radiation, emitted as a result of electrons traveling faster than the speed of light in water.

Only zero-rest mass particles can travel at the speed of light.[76] It is generally considered that it is impossible for any information or matter to travel faster than c, because it would travel backwards in time relative to some observers.[77] However, there are many physical situations in which speeds greater than c are encountered.

Some of these situations involve entities that actually travel faster than c in a particular reference frame but none involves either matter, energy, or information traveling faster than the speed of light in vacuum.

It is possible for the group velocity of light to exceed c[78][79] and in an experiment in 2000 laser beams traveled for extremely short distances through caesium atoms with a group velocity of 300 times c.[80] It is not, however, possible to use this technique to transfer information faster than c since the velocity of information transfer depends on the front velocity, which is always less than c.[81]

If a laser is swept across a distant object, the spot of light can easily be made to move at a speed greater than c.[82] Similarly, a shadow projected onto a distant object can be made to move faster than c.[83] In neither case does any matter or information travel faster than light.

In some interpretations of quantum mechanics, certain quantum effects may be transmitted at speeds greater than c. For example, the quantum states of two particles can be entangled. Until the particles are observed, they exist in a superposition of two quantum states. If the particles are separated and one of them is observed to determine its quantum state then the quantum state of the second particle is determined automatically and faster than a light signal could travel between the two particles. However, it is impossible to control which quantum state the first particle will take on when it is observed, so no information can be transmitted in this manner.

Another prediction of faster-than-light speeds occurs for tunneling and is called the Hartman effect.[84] [85] However, no information can be sent using these effects.[86]

Quantum field theory predicts an apparent superluminal propagation of photons due to vacuum polarization. This prediction raises the question of whether causality may be violated by quantum effects in curved spacetime.[87][88][89]

Closing speeds and proper speeds are examples of calculated speeds that may have value in excess of c but that do not represent the speed of an object as measured in a single inertial frame.

So-called superluminal motion is seen in certain astronomical objects,[90] such as the jets of radio galaxies and quasars. However, these jets are not moving at speeds in excess of the speed of light: the apparent superluminal motion is a projection effect caused by objects moving near the speed of light and at a small angle to the line of sight.

Čerenkov radiation

It is possible for shock waves to be formed with electromagnetic radiation.[91][92] If a charged particle travels through an insulating medium faster than the speed of light in that medium then radiation is emitted which is analogous to a sonic boom and is known as Čerenkov radiation.

Galaxies moving faster than light
See also: Metric expansion of space, Hubble's Law, Observable universe, and Cosmological horizon

In models of the expanding universe, the further things are from Earth, the faster they move away from us. This movement is not considered to be a straightforward travel, like a rocket for example, but a movement due to the expansion of space itself. This expansion moves distant objects away from us faster and faster the further away they are. At a boundary called the Hubble sphere, the recessional velocity is the speed of light.

At distances beyond the Hubble sphere, objects move away faster than the speed of light. One view is that this speed does not contradict special relativity because each observer is the center of their own Hubble sphere, so the motion occurs outside any particular observer's inertial frame.[93] A different explanation is that the "velocity" calculated this way does not correspond to a velocity seen in any single inertial frame, but is concatenated from distances observed in an infinite sequence of local inertial frames between the observer and the object (there are no global inertial frames), and special relativity refers to observations made in a single inertial frame, not an assembly of such frames.[94]

So it happens that we can observe galaxies that have, and always have had, recession velocities greater than the speed of light. The most distant objects that we can see now were outside the Hubble sphere when they emitted the photons we see now. The current recession velocity of the points from which the cosmic microwave background was emitted is v = 3.2c. We routinely see radiation from objects that lie outside the Hubble sphere.[93]

[357maximum]

[smilie=1: YALL MAKE MY HEAD HURT [smilie=1:


I would love to get my boolits up to the speed of light, but it is not something I am gonna persue for now.:roll:

[runfiverun]

boolits at the speed of light as i understand it would A. be so long it would fully be possible to shoot a one hole group.
B. so small they would be nearly impossible to measure.
and C. the boolits would be so heavy that you would not be able to hold up the rifle even if bolted to the earth.
and D. by the time you walked down to check your groups your brother would be dead and you couldn't brag to him about the group size.
:lol:

[StarMetal]

boolits at the speed of light as i understand it would A. be so long it would fully be possible to shoot a one hole group.
B. so small they would be nearly impossible to measure.
and C. the boolits would be so heavy that you would not be able to hold up the rifle even if bolted to the earth.
and D. by the time you walked down to check your groups your brother would be dead and you couldn't brag to him about the group size.
:lol:

About the A part. The way I understand it when an object approaches the speed of light it gets shorter. Example: A twelve inch ruler moved to the speed of light becomes shorter then 12 inches. Might explain why it gets heavier.

Felix,

The scientist talk about time travel using worm holes. From what I've read they are very interested in this. They speak of a parrallel universe on the other side of the worm holes, that indeed if they could build a device to travel the hole they could really travel in different times then the present time they were in. Man with him limited knowledge and his mathematical forums think that time is definite and not changeable. I on the other hand follow the group that say it can be changed.

Run,

With that new weapon we supposedly have, the laser gun for shooting down missiles etc.., depending on how fast that laser is, we may be shooting "bullets" the speed of light.

Joe

[Bret4207]

Rule #1- Never, ever try and best the rocket scientist by using science fiction.

[Whitespider]

Wow, I walk away from my computer for one day to spend the holiday with my kids and y’all take a discussion of ballistics into a discussion of quantum physics; how’d that happen? And some of y’all thought I was getting a bit too technical, geeezzzz! Well, quantum physics is a very interesting topic, but very, very hard for most people even to grasp the basics. I’d love to jump in, maybe quantify some of felix’s post with wording that the average genius would understand; but I’m afraid some of you would think I’m some sort of egg-head geek.

In any event, I was asked a couple questions...


Please explain to me why a bullet with a higher BC (this typically will be a bullet with a larger cross section for the wind to work on) that spends more time in flight, is LESS effected by wind drift ??
Well that’s easy... BECAUSE IT HAS A HIGHER BALLISTIC COEFFICIENT!!!! But time of flight is still the determining factor for each bullet; start either bullet at a higher velocity, so it reaches the target in less time, and the wind drift will be reduced. Assuming the sectional density of the two bullets is the same (i.e. same weight), a change in BC just changes how much effect atmospheric influences will have on the bullet in any given time segment. The BC did not, does not, determine the amount of wind drift, time does. Also, still assuming the sectional density of the two bullets is the same, both bullets would have the same exact surface area (cross section as you call it), just a difference in shape; anything else would be a physical impossibility.

Making a statement like "bullets with a higher BC will be affected by all factors less except time" is completely mind boggling. Especially when the earlier statement was "wind drift is determined by time of flight".
Well, I didn’t make that statement, what I stated was, ”A higher BC means the bullet will be less affected by all the variables, except time...” But my statement was incorrect, because a higher BC does not change the effects of variables like gravity. It should have read, ”A higher BC means the bullet will be less affected by all the variables that affect wind drift, except time...”

As to bullets in flight and gyroscopic precession, when an object that is functioning as a gyroscope has an outside force applied it moves in a direction 90 degrees from where the force was applied............correct ?? So we have a 3000 fps wind pressing on the nose of the bullet.....right ?? And we have a smaller wind created by the fall of the projectile created by gravity.......right ?? So with what we know about gyroscopes.......how will the bullet react to these two forces ?? By precessing............right ?? How will that precession allow the bullet to fly perfectly point forward ??
I never said that precession will allow the bullet to “fly perfectly point forward”, I said that the bullet does not fly constantly nose-up and to one side, which is also a physical impossibility if the bullet is under the affects of gyroscopic precession. There are two types of precession, torque-free and torque-induced. Only torque-induced precession is called gyroscopic precession, torque-free is called simply precession. Precession is the orbital motion of one end of the axis the spinning gyroscope. Check it out by clicking here. (http://upload.wikimedia.org/wikipedia/commons/8/82/Gyroscope_precession.gif)

When a bullet exits the barrel it is never released perfectly, because nothing is perfect. One side or edge of the bullet remains in contact with muzzle for just an instant longer causing the bullet to wobble, or go into precession as soon as it becomes gyroscopic. Because the bullet can’t go gyroscopic until all contact with the gun is removed, there is no torque applied to the gyroscope proper. This is torque-free precession, it is dampened by the forces of atmosphere, gravity and the inconsistencies of bullet material so each orbit of the bullets nose is tighter than the last until the bullet “goes to sleep” as we call it. Precession causes the nose to orbit around the line of travel so at any given instance the nose could be anywhere in a 360-degree circle around what would be a perfectly point-forward attitude. Of course the bullet never goes perfectly “to sleep”, there isn’t enough time.

When the bullet reaches the apex of its trajectory, and begins its downward curve, the gyroscopic force tries to hold the bullet in the same attitude as it was during the travel to the apex. This causes high pressure to build under the nose of the bullet, which pushes up on the nose. The gyroscopic force fights this upward pressure, which causes the bullets nose to rotate to the side of the high pressure in the direction of spin. Now the high pressure is on the side of the nose and it continues to rotate, down this time (below line of travel), then to the other side, then up. By now the downward trajectory has steepened and the high pressure under the nose is renewed and the cycle starts again, and than again, and than again throughout its downward trajectory. This is torque-induced precession (or gyroscopic precession), the nose of the bullet is orbiting around its general line of travel. This causes the bullet to “nose-over” and assume an attitude generally in line with its direction of travel.

There are TWO curves in the trajectory, one is caused by the rotation of the bullet, the other is caused by Coriolis force. The direction of rifling twist determines of the two will work against each other, or with each other.
The Coriolis Force, or more appropriately with ballistics, the Coriolis Effect does not alter the trajectory of a bullet. It is simply the appearance that the bullet is curving to the right if fired towards the north, or curving to the left if fired towards the south, because the earth is rotating. If fired due east or due west there is no Coriolis Effect. In any event, it does not cause the bullet’s trajectory to curve, it simply moves the earth bound target out of the way of the bullet.

[Bret4207]

WS- egg headed geeks are fine here. Gives the rest of us something to aspire to. Plus, slide rules are fun to smash flies with..........

[Willbird]

I agree on the the Coriolis Effect.

When the bullet is in the barrel it is rotating around it's physical centerline more or less, nothing is ever perfectly straight, concentric, or parallel.....but it is close. When the bullet exits the muzzle it transitions from that artificially induced motion to rotating around it's center of gravity.......the tough outer hide on some types of bullets is not a concentric tube, thus the bullet will have a different axis of rotation than when in the barrel.

This is all explained in "Rifle Accuracy Facts" by Dr. Harold Vaughn.

Modern rifle bullets typically are stable enough to be fairly accurate from the time they leave the muzzle until they drop subsonic, and in some matches they actually shoot accurately AFTER the bullets drops subsonic, I'm talking about Palma matches there.

Bill

[44man]

Hey fellas, did you see what Bass did to us? :groner:
He started this and left! :bigsmyl2:
May all of his boolits bounce off! :p