Twist, rpm, accuracy

[joeb33050]

This is where I am with the chapter for the book. I've asked Pat I. for a page or so on this since I can't find what he wrote previously.
The book is a summary of what we know, so if you have a correction or criticism or opinion; I want to hear it. However, my "theory bin" is overflowing. Hang on to them.
joe b.
TWIST, RPM, ACCURACY

Do bullets shoot more accurately with slower twists = lower RPMs; assuming stability of the bullets? Doesn't mean that the other variables don't count; they do.
We have some evidence that slower twists work better = better accuracy than faster twists at higher velocities and lower RPMs.
First is the 30BR light bullet slow twist for SCORE in modern benchrest. There's a lot on the 30BR and short bullets and slow twists at http://www.6mmbr.com/30BR.html
Second is the CBA experimenters shooting higher velocities with slow twists, accurately. See The Fouling Shot, Sept.-Oct. 2008, pg. 195-18.
Third is the results of Larry's Gibson's experiments, the results of which suggest that faster twist barrels run out of accuracy earlier than slower twist barrels, as velocity and RPM increase.
Fourth is from the Berger Bullets web site at http//www.bergerbullets.com

Q: What does the recommended twist mean?
A: We list a twist rate that will produce the best stability in all situations. Factors like temperature, elevation and muzzle velocity will affect how the bullet will stabilize. The twist rates we recommend will give you the best stability at the slowest twist possible. The recommended twist is based on a range of velocity so it is a guideline not an absolute reuirement.

Q: Why do you recommend the slowest twist?
A: Spinning a bullet faster than necessary can amplify any inconsistency in the bullet. Since we use J4 jackets you can shoot Berger Bullets in faster twist than what is listed. We list the slowest twist rate needed because we want to squeeze every bit o0f accuracy out of a rifle.

My interpretation of this set of 4 lumps of evidence is that there is a STRONG suggestion that stable bullets shoot more accurately with slower twist barrels at higher velocities = lower RPM.
Not proved, proving is hard and expensive. RPM is not the sole, and probably not the most important accuracy determinator.
All the other variables, ctg., powder, primer, bullet, alloy, lube, ........ affect accuracy. To some degree.
To make the suggestion STRONGER, we need more data.
But, my interpretation of the data/evidence we do have leads me to the conclusion that I will specify the SLOWEST twist that will stabilize the planned bullet on my next re-barreling of a gun. Because, at up 200 yards, I know of no evidence that a slow twist/stable bullet combination is LESS accurate than faster twists.
If Greenhill says that the minimum twist for stability is 1:17", I know of nothing suggesting that 1:<17" is MORE accurate. For a given bullet.
That's how I see it.

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





From the Berger Bullets web site:




I suspect that short light bullets are easier to shoot accurately, hence the references to 100-125 grain .30 caliber bullets.

Greenhill says that in 30 caliber, a 10" twist will stabilize a bullet 1.42" long, which would weigh ~250 grains. It says that a 15" twist, for examploe, will stabilize a bullet .95" long weighing ~166 grains. All Cast bullets.
I think it's clear that 30 caliber twists are generally "faster than needed", that slower twists with shorter lighter bullets are easier to shoot and torque on the bags less.
My impression is that gain twist and slow twist barrels are "easier on the bullet" as the bullet accelerates in rotation.

joe b.

[runfiverun]

it looks correct to me.
the term" best accuracy " breaks it down real quick.

[Larry Gibson]

Joe

Suggest you read; Ballistics, Theory oand Design of Guns and Ammunition by Carlucci and Jacobson. Google it and you should get some sample pages to read. Don't get bogged down with the math equations but pay attention to what they say. Also look at Dan Lilja's article on "A Look AT Bullet Imbalance and TWIST"." I think if you do a little more research you will find there is more than a "Strong suggestion" that slower twists giving less RPM give better accuracy. There is a lot of scientific information out there that will or should lead anyone to more than a strong conclusion regarding barrel twists and the effects of RPM on bullets, jacketed and cast.

Larry Gibson

[Wayne Smith]

I don't know if you have addressed this elswhere in the book, but people should be reminded that the original Greenhill formula was developed for artillery shells and may need some modification to use with boolits.

I assume you are well aware of this, just reminding you. I know how easily details can sometimes get lost.

[Larry Gibson]

I agree with Wayne. While the Greenhill Formula and the most usual other one used (forget the name - CRAFT) most often work quite well for jacketed bullets. However they fall short with cast bullets. The other one is the formula that gives a factor of 1.3 as stable and 1.5 and maximum stability. That formula seems to work ok if the cast bullet is longer than 1". However shorter cast bullets like 311291 or 31141 all give results that seem to be in left field.

Larry Gibson

[44man]

There is a lot more to it then what is stated. It is true that if you shoot only to 200 yd's, over spinning a bullet will open groups because of the high RPM's making the bullet rotate around the flight path. Many of these conditions work themselves out at 300 yd's and farther and long range groups can be much smaller then close range groups. Close range target shooters lean towards slower twists.
If all shooting is done at extreme range, I would not go with a slow twist. I see it all the time with my BPCR where I have shot sub 1" groups at 200 meters but the entire berm and the hills behind it are safe at 500 meters. Creating this underspun condition makes it very hard to find a boolit that will be stable at long range and a very tiny change in the boolit has a profound effect. This can be seen clearly with the Marlin .44 and the 1 in 38" twist. A boolit can be made to shoot way under an inch at 50 yd's yet will not stay on paper at 100. Once the velocity bleeds off, the boolit goes unstable like the gyroscope that starts to wobble all over the table.
Another thing never mentioned is barrel length. What effect does a certain twist rate have with a revolver barrel of, say, 7" compared to the same twist in a 24" barrel? Now how about a 3" barrel, if the velocity is the same with all three examples. Will a 3" barrel impart the same RPM's on a boolit that the 24" barrel does?
I don't know the answer to that! But in the real world, the velocities are very different for each length and spin will be very different. A heavy boolit that shoots great at the rifle velocity can not be spun up enough in the short barrel because of the velocity limit.
I would still prefer a little faster spin because it is easier to slow down the bullet for close range and you can speed it up for long range. The faster twist rates are not as picky with different bullets either. With a slow twist, you might only find ONE bullet.
Caliber also has a large effect. I have a Swede that will shoot every weight bullet from 100 gr's to 140 gr's to the same POI and less then 1/2" groups at 100 yd's. and all of you know about the super fast spin rate they have.
Everything so far stated in the posts are correct if you sit at a bench punching tiny holes in paper but let's face it, most of us here do not shoot BR and many are hunters. If all the different boolits/bullets used by all of us are listed, it would take a week to read them all.
Even with revolvers, twist is very important and the absolute, most accurate are the BFR's. I have shot 500 meter groups with them that are as good as a lot of other revolvers get at 25 yd's. The twist rates are FASTER then all the other revolvers. The BFR 45-70 has a twist of 1 in 14". It has kept 5 shots in 7/16" at 50 yd's, shoots under an inch at 100 and shoots better then most rifles at 500 meters.
Would I trade for a slower twist? Not on your life! :Fire:
All of this slow twist talk is moot unless the use of the gun, the distances shot, the bullets intended to be used and a thousand other things are also figured in. I would never tell anyone to buy a slower twist then normal because I know he will be disappointed if he is a normal shooter with 4 or 5 boolit molds.
Greenhill can not be adjusted to fit everything. You might do it for ONE boolit in ONE barrel at ONE velocity. Even then it will give too slow of a twist for usefulness. So what do you do? Try to make it fit all the other combinations? [smilie=1: Seems to me you can find what your gun shoots best and then make Greenhill agree, backwards if you ask me.

[felix]

44man, freebore is the main killer with boolits. Revolters have plenty by definition. You need to check the difference of land impression on a fired boolit with the land width in the barrel. If the difference is very, very close to zero on the BASE of the boolit, then that boolit got the full rotation as prescribed by the twist. You might find that this difference is not zero, especially up towards the nose, which implies slippage, and that would be expected with such a big diameter boolit. The accuracy you describe indicates your boolits do indeed get enough rotation, slippage or no slippage. Something to check out. In other words, the twist formulas assume 100 percent land grabbing at least at the boolit tail. ... felix

[Bass Ackward]

Joe,

You have nailed this perfectly. I wouldn't change a word. Publish it for all posterity.

About time that those CBA benchrest boys learned that they all should be shooting 38 twist 44s or 45 calibers instead of playing with those RPMy toy guns that just aren't capable of being accurate.

[leftiye]

Starts to sound like slow twist is a one boolit special scenario sometimes. Like my pustulating on another thread about minimum lube capacity grooves and a super lube. You canonly make it work with that good of a lube (though it may well work superbly)..

[Pat I.]

All of this slow twist talk is moot unless the use of the gun, the distances shot, the bullets intended to be used and a thousand other things are also figured in. I would never tell anyone to buy a slower twist then normal because I know he will be disappointed if he is a normal shooter with 4 or 5 boolit molds.

I'd agree with a lot of what you're saying if 99% of the people were shooting 500 yds and beyond but since it's more likely the exact opposite where the 99% are shooting 200 yds and below I don't think too many would be disappointed with a slower twist.

I'll agree with you that sometimes a group farther out might have a smaller MOA than a group shot closer but thinks it's impossible for the actual group size to be smaller unless affected by outside influences.

I know it's often stated that most of you here don't shoot benchrest but if you're shooting a rifle off a bench it's benchrest and you're doing it to try to achieve the best accuracy you can get. If you think about it that way how many don't shoot benchrest??

[44man]

Felix, you are entirely correct. ALL of my best shooting revolver boolits show a wider land mark at the top of the boolit but are at the proper dimension at the boolit base. I understand this and have ignored it when accuracy is at it's best. It really means little and can't be fixed without going to condom bullets anyway. The only other option is a gain twist.
My 45-70 BFR has a HUGE space to move before the forcing cone and rifling is reached. But it has zero effect on accuracy.
It takes a God awful slow boolit to get the same size marks from the lands.
Lead is soft no matter what the alloy. There is no way to engage and hold rifling marks evenly with ANY high velocity. And trying to estimate the RPM's a boolit goes to pot might actually be the point a boolit skids a long way down the bore and the gas seal is destroyed and NOT that it is spun too fast.
The 6.5 Swede also has a very long freebore and it does not effect accuracy but beware using too slow a powder because SEE can happen.
All of these tests being done are ignoring other factors that come into play to destroy results and the blame is placed on other then what might be the real problem. If a super fast boolit strips the entire length of the barrel, how can anyone say it was spun too fast????? There is NO WAY to isolate only one condition.

[Larry Gibson]

44man

You have it a little backwards. Not debating the accuracy results you observe but there is probably another reason. Slower twists are selected for accuracy at longer range as long as the bullet is stable at the muzzle. Velocity decays a lot faster than RPM. Thus as range increases there is a higher RPM to velocity ratio and the bullets become more stable. A bullet that is at maximum stabilization or over stablized at the muzzle is really over spun as range increases. Accuracy may very well result from that with both cast and jacketed bullets.

Larry Gibson

[joeb33050]

44man

You have it a little backwards. Not debating the accuracy results you observe but there is probably another reason. Slower twists are selected for accuracy at longer range as long as the bullet is stable at the muzzle. Velocity decays a lot faster than RPM. Thus as range increases there is a higher RPM to velocity ratio and the bullets become more stable. A bullet that is at maximum stabilization or over stablized at the muzzle is really over spun as range increases. Accuracy may very well result from that with both cast and jacketed bullets.

Larry Gibson

The BPCR guys disagree, and with a lot of shooting and data. It seems that a given bullet/twist combination is stable at shorter ranges and becomes unstable at longer ranges. This with big bores and slow velocities. This is addressed in the book, with alternatives to Greenhill. The RPM:Velocity ratio doesn't seem to control.

BTW, look at Lilja/Twist, see another stating that slower twist = better accuracy-his article derives from Col. Harrison's work.

While we don't have much DATA, the opinions of respected folk are clustering about the minimum twist notion.

joe b.

[joeb33050]

Joe,

You have nailed this perfectly. I wouldn't change a word. Publish it for all posterity.

About time that those CBA benchrest boys learned that they all should be shooting 38 twist 44s or 45 calibers instead of playing with those RPMy toy guns that just aren't capable of being accurate.

I can't decide if you didn't read it, can't understand it, don't agree with it, are being difficult, or just don't express yourself well. I have always had a tough time understanding what you write. It ain't me.
Respectfully Yours;
joe b.

[joeb33050]

44man, freebore is the main killer with boolits. Revolters have plenty by definition. You need to check the difference of land impression on a fired boolit with the land width in the barrel. If the difference is very, very close to zero on the BASE of the boolit, then that boolit got the full rotation as prescribed by the twist. You might find that this difference is not zero, especially up towards the nose, which implies slippage, and that would be expected with such a big diameter boolit. The accuracy you describe indicates your boolits do indeed get enough rotation, slippage or no slippage. Something to check out. In other words, the twist formulas assume 100 percent land grabbing at least at the boolit tail. ... felix

I used to believe that freebore business until I got the Competitor pistol, which is chambered such that the base of any cast bullet I have, dropped in the chamber, is .15"-.4" in FRONT of the case mouth. Any bullet seated GC in mouth of the 30BR case comes nowhere near touching the rifling. But the gun shoots. (10" twist GM barrel)
Baffles me.
joe b.

[joeb33050]

I don't know if you have addressed this elswhere in the book, but people should be reminded that the original Greenhill formula was developed for artillery shells and may need some modification to use with boolits.

I assume you are well aware of this, just reminding you. I know how easily details can sometimes get lost.

I love and admire Greenhill, have never know forecast to fail at reasonable V and shorter (vice BPCR) ranges. Twists of many rifles are published and available. Compare the twist used in the rifle, commonly used bullets, length of those bullets and Greenhill. You'll shortly become a convert.
joe b.

[44man]

44man

You have it a little backwards. Not debating the accuracy results you observe but there is probably another reason. Slower twists are selected for accuracy at longer range as long as the bullet is stable at the muzzle. Velocity decays a lot faster than RPM. Thus as range increases there is a higher RPM to velocity ratio and the bullets become more stable. A bullet that is at maximum stabilization or over stablized at the muzzle is really over spun as range increases. Accuracy may very well result from that with both cast and jacketed bullets.

Larry Gibson
Now you are getting confusing! :confused: Stable at the muzzle means nothing at range. You are correct that spin decays at a slower rate then velocity but then you agree with me that over spin can result in better accuracy at long range! Isn't that exactly what I have been saying all along? You are agreeing with me and telling me I am wrong in the same sentence.
Spin stabilization is always more important then velocity.
We are BOTH agreeing that a boolit spun too slow will lose stability at long range and that a faster spin at the muzzle can give better accuracy at long range even if the stability at the muzzle is less.
We are BOTH right but you keep saying I am wrong. It is time for us to get together! :drinks:

[44man]

I'd agree with a lot of what you're saying if 99% of the people were shooting 500 yds and beyond but since it's more likely the exact opposite where the 99% are shooting 200 yds and below I don't think too many would be disappointed with a slower twist.

I'll agree with you that sometimes a group farther out might have a smaller MOA than a group shot closer but thinks it's impossible for the actual group size to be smaller unless affected by outside influences.

I know it's often stated that most of you here don't shoot benchrest but if you're shooting a rifle off a bench it's benchrest and you're doing it to try to achieve the best accuracy you can get. If you think about it that way how many don't shoot benchrest??
Pat, I spent many years shooting varmints at long range, to better then 600 yd's. My long range rifle would NOT shoot small groups at 100 yd's. But the rifle would shoot 5 shots into 1/4" at 350 yd's and I could head shoot chucks to over 600 yd's.
I suggest you take a spotting scope and watch bullets fly for yourself. Experience is the ultimate teacher, not some book crap.

[Larry Gibson]

Joe and 44man

I am not confused at all. Remember I told 44man to basically look for other causes. The other cause is "It seems that a given bullet/twist combination is stable at shorter ranges and becomes unstable at longer ranges. This with big bores and slow velocities. " The bullets become unstable at the longer ranges because the velocity is low for the weight of the bullet and twist relationship and thus the bullet is only marginally stable at the muzzle. It was determined many years ago by Frankford Arsenal (1880s) to be exact that the 22" twist was as accurate as the then in vogue 18" twist out to a very long range (past 1000 yards) with the 500 gr m881 service bullet. BPCR guys started shooting 500+ gr bullets that were only marginally stable at close range and then were even more unstable at longer range in 22" twists. They then went to 18" twists and then to faster twists as velocities got lower with heavier and heavier bullets. It's funny you mention this because that's exactly why Frankford Arsenal ran their test in the 1880s because the target shooters were using 18" twists with heavier bullets than 500 gr and Frankford Arsenal proved to their Army marksman that the 500 gr M1881 bullet was just as accurate out of the 22" twist of the TD out past any distance they were target shooting at. The 500 gr RN service bullet was at maximum stability in a 22" twist. A sharp pointed 500 gr bullet or 500+ gr bullets become marginally stable out of the 22" twist of the TD. Twists of 18" or faster are required to bring those bullets to maximum stability, especially at the slower (1100 fps and less) velocities used with those heavier bullets.

The BPCR boys are simply matching the twist of the barrel to the weight of the bullet and the muzzle velocity used to bring the bullet to maximum stability at the muzzle so the bullet maintains stability across the spectrum of flight. Not rocket science. The heavier bullets the BPCR boys becan to use were marginally stablized at the muzzle. This means accuracy may have been good at 100 yards or even 200 yards but beyond that they lost accuracy rapidly because the bullet was only marginally stabilized to begin with. Note that I stated; A bullet that is at maximum stabilization or over stablized at the muzzle is really over spun as range increases. I said "maximum or over" not "minimum". This is why 44man's faster twist revolvers are also very accurate at long range. The post I made is still correct.

BTW Joe; I advised you to read Lilja on barrel twist. He is correct. Note that "slower twist is better" as long as the bullet is at maximum stability at the muzzle, not at the minimum level of stability at the muzzle. That is what the BPCR boys understand and agree upon. I agree with them and my post agree's with them.

Larry Gibson

[Larry Gibson]

44man

[I spent many years shooting varmints at long range, to better then 600 yd's. My long range rifle would NOT shoot small groups at 100 yd's. But the rifle would shoot 5 shots into 1/4" at 350 yd's and I could head shoot chucks to over 600 yd's.
/I]

1/4" at 350 yards! [I]That is .07 moa!!!!!! Your level of accuracy that you manage with everything you shoot astounds me! Why is it we do not find you as the reigning champion at all the National matches (rifle and handgun) at Camp Perry?

Larry Gibson

[Pat I.]

Pat, I spent many years shooting varmints at long range, to better then 600 yd's. My long range rifle would NOT shoot small groups at 100 yd's. But the rifle would shoot 5 shots into 1/4" at 350 yd's and I could head shoot chucks to over 600 yd's.
I suggest you take a spotting scope and watch bullets fly for yourself. Experience is the ultimate teacher, not some book crap.

Then you have a magic gun. Think about what you're telling me. I agree the MOA might be smaller at a longer distance because once the bullet settles down it's BC improves and wind won't have such an effect but to tell me that a gun that shoots 3/4 at a hundred all the sudden shoots 1/2 at 300 without an outside influence such as wind pushing it back together is just plain wrong. What the heck could people possibly think would be the reason for 5 bullets that start off on a course that would lead to a one inch group at 100 yds. all the sudden decide to change course in midflight and snuggle back together?

As for your inuendo that everything I know I learned by reading some "book crap" isn't worth responding to so I won't bother although if the book I was reading made some of the outlandish claims I'm reading in this thread and others I'd throw it in the trash.

I should mention to you though that your quarter inch 350 yd groups is only .100 less than the best 300 yard 5 shot aggregate that's ever been shot in a jacketed National Benchrest Shooters Association match so you might be in the wrong game shooting cast bullets.Those guys can win some big money and your varmint rig looks like a shoe in.

[44man]

Larry, I was not in any competition in those days. The rifle was a pre 64 Winchester 70, 220 Swift, glass bedded and floated. I used a 60 gr Hornady. Roughly 3800 FPS.
I NEVER shot under 1" at 100 yd's and would have never known how it shot at long range if I had not worked with it. Yes, I almost gave up the load until I seen what it could really do. It is NO mistake, it really shot that good.
Over spin at the muzzle? Don't try to convince me! [smilie=1:
Back to the BPCR. The 500 gr round nose government boolit will out shoot any other 500 gr boolit made and it will do it with a variety of twist rates.
Pat, take a spotting scope and watch 240 gr bullets go down range when shot from a S&W 29. That is the easiest thing for you to see.
Come back and tell me I am wrong!
Watch the 308-165 SIL boolit shot from a 30-30 TC swing so far to the side at 200 meters that it looks like it will hit the next ram in line, then go back and center the ram it was aimed at. Tell me I am crazy. You are book reading not doing! :roll:
99% of you have never actually watched bullets in flight, you only repeat what you read or what you guess at. How about a hint? They do some crazy ass things! :drinks:

[44man]

Larry, I have watched thousands of boolits go down range from BPCR's. When you see one go straight to just beyond 200 meters, then head off to the wild blue yonder, please come and explain to me what happened to the boolit. Over spun, under spun, transition to subsonic (Some start subsonic!) Wind, rain, sun, the boolit genie? Oh I see, the wrong Greenhill figures! [smilie=1:
Spend a few years shooting BPCR, the very HARDEST shooting sport on earth. Come back and tell me what I need to improve my scores. I believe you will be humbled as I am! :roll:
I could do better with my revolvers.

[Larry Gibson]

44man

Sorry to burst your bubble but there are many of us who have watched bullets or bullet traces go down range. Not sure what makes you think I've not loaded, shot and watched a few BPCR bullets go down range. As to what causes a bullet to "head off to the wild blue yonder"? I'll assume you're not referring to a bullet being caught by a sudden wind but one that just goes anywhere with no consistency. I'll refer you to my post to Joe.

If a bullet is fired at low velocity to begin with and in a slow twist where the bullet was marginally stable at the muzzle Then at some point the bullet will lose all stability when the velocity gets low enough. This happens at some distance as the velocity decays due to air resistance. At that point even the increased RPM to velocity ratio isn't enough to keep the bullet stable. The bullet may tumble off into never never land or the radius of gyration may increase to the point the bullet strikes the ground, a berm or flies off and you lose sight of it in the scope. I really don't want to bring up RPM again but it does play a part as the RPM does not decay significantly as the velocity does. Another good place to observe this is with pellet rifles at longer ranges (longer ranges can be as little as 50 yards for WC type pellets) and match or subsonic .22LR shot in fast twists such as 7" at longer ranges. With a decent scope and heavy rifle with no recoil you can watch these pellets and bullets "lose it" past a certain range. Same thing also hapens with some "cat's sneeze" loads in rifles when using long heavy cast bullets at 300-400 fps. The bullets at some point decay velocity wise until the static stability is over come and they fly off to never never land. Not rocket science.

Shooting like you do I can't see how you need to improve your scores, they should be quite impressive. I certainly can't tell anyone who shoots 1" groups with revolvers at 100+ yards or .07moa at 350 yards with a rifle how to shoot. You are certainly above my skill level.

Larry Gibson

[44man]

But you see Larry, we have both been saying the exact same thing and we DO agree on all of it. :brokenima
Please explain to Pat how crazy a boolit can act! :Fire:

[Pat I.]

I'll agree minus the effect of wind there's some craziness involved here. :groner:

[Tiger]

Why why why every time rpm thread start I get only few posts and then it is closed?

Larry you bring to attention watching tracer bullets in flight. I think with your lengthy military service that there is no question that you have seen them in flight. I like to mention that watching flight of tracers is a bad example of how normal bullet would fly. I say this because who to know if the trace cavity in bullet in perfect center in bullet. Who to say as the trace burns that it burns even at its base. Too as it burns bullet is changing weight and center of gravity. I might add that perhaps the trace burning may have little rocket thrust effect hey. Throw in when tracers used in aircraft the much different extreme wind influences.

One last thing. Larry remember my last time post about Mr Jones "going to sleep" article at high rpm. He say if you forget that faster bullet rpm cause bullet to take longer distance to settle down. I have seen what 44 man say about his 220 swift.

Please do not call names and argue much to cause thread closed.

Ralf

[Larry Gibson]

44man

We do all agree (you, Pat and I). I think we were all saying the same thing just in different ways. Pat and I understood your explanation to Joe and just put it in different words. It is amazing the things that effect a bullet in flight.

Larry Gibson

[Larry Gibson]

Tiger

The tracer's changing of weight distribution (unevenly) and the adverse affect the RPM then has on the bullets flight was the example I meant to use. You are now saying and agreeing with me only using different words just as with 44man, Pat and I. We are on the same page of the Hymn book.

Who said we're argueing? Bullets "going to sleep" is not an issue. This was discussed and put "to sleep" (pun intended) in another thread. The only issue is groups getting smaller at long range. They may stay the sam size. They may also appear to shoot smaller groups but that is based on too small a sampling of each shot within the cone of fire (something about "random dispersion"). Bullets "going to sleep" happens but it has nothing to do with accuracy getting worse, ok.

Larry Gibson

[Bass Ackward]

I can't decide if you didn't read it, can't understand it, don't agree with it, are being difficult, or just don't express yourself well. I have always had a tough time understanding what you write. It ain't me.
Respectfully Yours;
joe b.


Joe,

It's all of the above. And I " KNOW " that you don't understand. I will try to explain because you aren't the only one.

You have to understand that back in the late 60s or early 70s we went to our first NRA gun Show held in Washington, DC. We were just getting started making rifles and sources for actions were hard to come by then without buying factory rifles and tearing them down. One of the booths we went to was the Sierra Bullet booth. There was a mini convention there of sorts and one guy from Sierra was there spouting his wiz bang, sure fire, mathematically supported RPM theory. There was also guys who considered themselves experts there from several different companies to include old man Shilean and several other folks just nodding their heads up and down.

While we went there to get information we left with theories about why 8.66 twist Mauser's couldn't shoot light bullets accurately. Why Mauser actions were incapable of accuracy do to the heavy hammer fall and long / slow lock time. Since then we hear the merits of plastic stocks. How sporter barrels aren't as accurate as heavy barrels. How fluting is going to sweep the industry. How fiberglass encased barrels are the new wave. Electronic ignition is the cats meow. Inherrent accuracy of some cartridges. (mostly driven by bore size and recoil by the way) All of that was crap!

The fella spouting the RPM theory was totally lost. Says something for the accuracy potential of Mauser actions too. And the lock time theories and on and on because we guaranteed accuracy below an inch with factory ammo if available, so the guns had to perform. The 8.66 twist Mauser's were the most accurate with 115 grain Speer hollow points and would cluster these into 1/2" groups because the bullets were tough enough to hold the rifling. Something in a light Sierra would not do at the time and you had to have a longer (heavier) bullet to hold up. So because Sierra had a problem with their soft bullet material, (they still do by the way) they came up with an RPM theory as to why light bullets went RPMy. (Sounds like cast huh?) To this very day, Sierra jackets shed the easiest and fastest in the industry. So they probably are still lost and have their RPM theory as Larry quoted it.

Long before this time I was shooting a 30-378 Wby with 150 grain bullets outta 30" barrels for long range groundhog hunting out to about 1200 yards before many people ever heard of the cartridge. If you think that doesn't turn some RPMs, you need to do the math. Accuracy even at 100 yards was in the tenths for a massively overbore cartridge. But you had to hold it. The bigger the cartridge, the longer the barrel you need to maintain accuracy to lower muzzle pressure just in case you didn't know. Otherwise the barrel looks RPMy. But it was statistically harder to hold.

There is one gun in this world capable of "best accuracy" because it set the world record. Nobody asks that shooter to shoot that record three times to verify that it wasn't a fluke. If you handed that rifle to 10 other guys, chances are 9 of them would shoot close to an inch and claim the rifle just another gun.

We find a majority of shooters can experience MOA, some with less work than others, but that is it. About three in ten can experience 1/2" on a consistent basis. I shoot all the time but 1/2" is the best I can do on a reliable basis with jacketed or cast. So I know that I can't do much better now. Man has to know his limitations. Shooting a right hand roll over cheak piece in a 378 Wby when you shoot left handed will ruin anyone.

In other words, ringing the accuracy out of a gun and accuracy theories are generally driven by recoil and vision more than any other factors. Guess where you get the least recoil? Smallest cartridges at the lowest RPMs, least heat, least fouling, and barrel vibration and on and on. Does that make them more accurate? Or less idiot proof?

Back to a child's toy, the top. You can take the same, exact top and have 10 people spin it. 7 to nine people will spin it about the same RPM and there will be 1 of the ten that can spin it the longest (highest RPM). Is it right to theorize that because of over whelming statistics, that the top has an RPM limit? Or should we admit that we just can't do it as well as the one guy? The answer depends on where in those statistics you fall as misery loves company.

The most accurate rifle I ever had my hands on was a 378 Wby that at 7 1/2#, 99 other guys couldn't get to hold 2". Yet statistics prooved that gun was inaccurate. (Right.) People get so consumed about why they can't instead of figuring out how they can. If a parer patched molded lead bullet can fly accurately at jacketed bullet RPMs and velocities, then it ain't imbalance or flying apart or bending or the lead or RPMs that's causing the problem. If you spin it slower will you cause less damage in the bore? Yes, less rotational force. Simple. Does a lighter / shorter bullet that goes faster require a harder jacket than a long heavy one that can't go as fast? Yes? Does that justify the RPM theory? Only if you don't understand and you need math to make you sleep better.

Same as with your 223. Remember that? I told you to use the lightest weight bullet and the slowest powder. You didn't listen then either as you bought the 70 grainer and used monotype. But I did get you the best accuracy you achieved using 4350 in that gun and I never saw the gun. Was it good enough to compete? THis is kinda personal, are you? Had you listened and went with the lightest weight bullet that would fit your throat and used softer metal, you "could be" on this side of the RPM argument now. So I " KNOW " that you don't understand. :grin:

Want to get better statistics for RPMS and cast bullets? Set a minimum of 2500 fps for competition and let competitors live with poor results for a few years. Necessity is the mother of invention and eventually it will happen. Answers will be achieved. Until then we will get theories why it doesn't and call people liars that luck into it themselves. Or say they aren't competitent because they don't compete. Just like the top, your position on RPMs is where you find yourself in the statistics.

Can I say it any plainer than that?

[Pat I.]

I and a few others shoot faster than 2500 fps and don't do too bad, if you don't consider one of us, not me, winning the CBA national match last year poor results.

Well I guess the answers lie in the fact that some people are just much better shots then the rest of us and everything all the bullet, action, barrel, stock, ballistic experts, and everyone else that has anything to do with shooting and have the equipment and testing facilities available to them to really wring out the whole kit and kaboodle are full of crap. Sounds reasonable to me

Liars is sort of a strong word, lets use unconvinced instead.

[Larry Gibson]

Joe

Actually that explanation of Bass's was not very plain, at least to me anyway. Sounds like he really has a problem with adverse affects of RPM and just doesn’t understand it as perhaps he is suffering from “RPMy”. Let’s simplify this a bit and use jacketed bullets since that’s the gist of Bass' post.

Take the .223 for instance and use 52-55 gr bullets at 3200 fps, a pretty standard velocity. Now the only thing we’ll change is the twist of the barrel…same load with the same velocity but only a different twist….understand? Start with Hornady 55 gr SXs and Sierra 55 gr Blitz’s. Shoot them in 12” and 14” twist and you get wonderful accuracy. Shoot them in 9” twists and sometimes you get accuracy and sometimes you don’t because some of the bullets fly apart about 40-60 yards from the muzzle and don’t make the target. Try then in a 7” twist and very few will make it to a 100 yard target. So then let us consider the 52 gr Speer HP and the Sierra 52 gr match HP. The Speer has a thin jacket designed to explode on varmints. The Sierra on the other hand has a stronger thick jacket to hold together at high RPM for maximum accuracy. The Speer will spin apart sometimes in 9” twist and most always in the 7” twist yet the Sierra 52 gr match holds together and is accurate in the 7” twist.

Now let us ask ourselves why that is? Could it be that the increased twist is increasing the RPM? Could it be that the centrifugal force of the RPM is spinning the thinner jacketed varmint bullets apart? Let see; the RPM is 192,000 from the 12” twist, 226,000 from the 9” twist and 331,000 from the 7” twist. Hmmmmmm…the only difference being 190,000 RPM = good accuracy, 331,000 RPM = no accuracy. If it walks like a duck and quacks like a duck then perhaps it is a duck. Not rocket science.

Not enough? Ok, let’s look at the 6.5x55 Swede with it’s 7 ½” twist. Two 100 gr varmint bullets; the 100 gr Hornady SP and the 100 gr Sierra HP. The Hornady has a much thinner jacket than the Sierra. At a velocity between 2900 and 3000 fps the Hornady will lose accuracy and if pushed to 3200 fps will sometimes disintegrate in flight 40-60 yards from the muzzle. The thicker jacketed Sierra on the other hand shoots exceptionally accurate at 3200 fps. At 2900 fps the RPM is 278,400 and at 3200 fps the RPM is 307,200. The thicker jacket of the Sierra allows it to withstand the increased RPM. It’s walking and quacking like a duck …..again, not rocket science.

Still not enough? Take the Speer 125 gr TNT made to expand at pistol velocities and a Speer 130 HP made with a thicker jacket. Run them up to max in a .300 Winchester with 10" twist and see what happens. It will be the very same thing, the increased RPM with cause the TNT bullet to disintigrate well before the 130 HP. It is simply because the heavier jacketed 130 HP is made to withstand the higher velocity/RPM. All of Bass' examples of success were simply because he had a bullet that could withstand the RPM. Again, not rocket science.

Granted Mauser actions can provide some pretty good accuracy but it is well known by everyone, except perhaps Bass, that they are not the most accurate of bolt actions. However they do for my needs many times. Actually 2 of the test rifles in the RPM threshold test were M98 Mausers and the 3rd is a M70, pretty darn close to a Mauser eh? Not sure I see Bass' point there other than he disagreed with a factory salesman. Most of us don’t find that too hard to do.

Bass states; “Want to get better statistics for RPMS and cast bullets? Set a minimum of 2500 fps for competition and let competitors live with poor results for a few years. Necessity is the mother of invention and eventually it will happen.”

Very good idea for Bass! I’ll bet the first thing to happen is the twists will get slower to reduce RPM…..oops….it’s already been done….oh well, it was a good idea, sorry Bas but you're already too late…….

Seems Bass just mentioned competition as the way to answer the question and then contradicts himself about those who “luck” into “it”. Is a lucky group (random dispersion) or two proof or is it “luck”? Which is better proof of a theory; consistent reproducible accuracy or random dispersion group “luck”? Joe, I guess Joe gets to pick which one he wants to go with or he can be politically correct and use both. Depends on whether you want your book to be “definitive”?

As to Bass' inference about calling people “liars”, I agree with Pat, that is pretty strong. Obviously some are just "unconvinced".

Larry Gibson

[44man]

Rifles are funny. Old military rifles can not be matched by many sporting guns. There was a period where any make rifle off the shelf with some tweaking of the bedding would be a tack driver. Then there was a long stretch where accuracy seemed to just go away except for Weatherby and Savage. Now we have entered a new era where rifles, handguns and factory ammo is as good as it gets. ( I still read in Handloader that revolvers are not accurate enough to worry about.)
Most of you know military rifles have pretty fast twists.
Lately I had to mount scopes on 3 Weatherby Vanguard rifles and sight them in. One was a .243, one a 30-06 and one in .300 Weatherby. I bore sighted by eye at 100 and started to shoot. The .300 took 4 shots, the rest took 6 each. My last 2 shots with each were in less then 1/2" right at the point I wanted them. Amazing for factory loads and rifles right out of the box.
Now, years ago when I got my 1919 Swede, 6.5 X 55, I shot it with 129 gr Hornady bullets. It shot too high so I soldered a piece on top of the front sight. Went back down and it shot low so I filed the sight after each shot and bumped the sight sideways a little. I got in the black, low, filed some more and took 3 shots to finish.
There was a coke can on the ground at 100 so I shot at it off hand. It didn't move so I shot again and it still didn't move. I went down to get my target and this is what I found. My last three were in the center, .432". But look at my two on the can!
Full military garb! Open sights. The bore is also pitted some.

[Larry Gibson]

44man

That's some fine shooting with some fine rifles. I had the pleasure of shooting a new Weatherby in '06 a few months back. The owner only had factory ammo (I think it was Federals top end stuff) and I was pleased with the accuracy as I shot two 3 shot sub moa groups with it. Aren't they guarenteed for 3 shot sub moa? Anyway they are fine shooting rifles.

The Hornady 129 has always been one of my favorite 6.5 bullets. Used it for years in my 6.5-280 and 6.5 Swedes. Always an accurate bullet. My 6.5 Swede scout will consistantly put 5 of them into 1 moa or less. It only has a 2X scope. With my M96 and its long sight radius and my old eyes I've shot many a 1 moa 5 shot group with them. I used to win the local (Paul Bunyon Range) military rifle match with my M96 using the 129 gr Hornadys. The match was usually 10 shots bench, 10 shots standing, 10 shots sitting and 10 shots prone all at 200 yards. The bench match was for score and group. The other guys would always groan and moan if I pulled that rifle out to use. So I pulled out my M24/47 8mm and won. Then at another match I pulled out my M39 SAKO Finn and won. They don't like to see me show up period now!

Larry Gibson

[44man]

Larry, the fast twists on the .223 were for hard military ammo to cause more damage to the enemy and for the use of heavier bullets. Of course light, thin skinned sporting bullets will blow up. Does that prove anything? Download and you will find good accuracy at some point.
The twist rate is made for the common bullets shot and when you exceed either the twist rate or the bullets intended, results go to pot. However, reduce the twist rate and things can go bad a whole lot faster as far as accuracy, mostly at longer ranges. You just can NOT dispute that fact. In fact you have agreed with all I have said.

Bass is correct in stating many Sierra bullets are too soft, too thin and open way too fast on game. Bullets are made for different uses and most target bullets should NEVER be used for hunting because they are TOO hard and will not expand. The Sierra target bullets ARE tougher then their sporting bullets so we can't compare apples to oranges here.
I have Speer target bullets here that are so accurate as to be scary. I contacted Speer and they told me "Do NOT hunt with them." Nuff said?

[Larry Gibson]

44man

Other than the faster twists in the military 5.56 were not "for hard military ammo to cause more damage to the enemy" we are all in agreement over everything you said. Any reason to think otherwise?

Bass went off on the sales guy about some RPM theory (appears to be totally different from the RPM threshold and cast bullets) and shooting light bullets in "8.66 twist Mausers" (Mausers have 9 1/4" twist BTW). I was pointing out to Joe that Bass wasn't quite correct about the sales guy being "lost" and that there might have been something to what he was saying. There is something to RPM effect even with jacketed bullets. As you just said; we agree on that. I also pointed out that I found Mausers perfectly adequate also, just like Bass. Since the most winners in many,many rifle matches use Sierra bullets I doubt they are "lost" either as Bass said they were. I'll not disagree about Sierra's shedding their jackets as they are mostly simple cup and core bullets. However the Sierra 100 gr HPs in 6.5 and the Sierra 125 SPs in .30 cal (just two examples) hold up to about as high velocity as you want to push them along with numerous other Sierra bullets of most calibers. We are talking about external ballistics here and bullets that are disrupted by RPM not terminal effects. There are Hornady and Speer bullets (mentioned in my post) that don't hold up any better than Sierra's. It is a simple matter of the jacket construction and what they are designed for. Push any bullet outside it's design parameters and bad things can happen. Not sure how the question of using jacketed match bullets for hunting got into the conversation?

BTW; The original AR15 and the first (greengun) XM16s had 14" twist so the 55 gr M193 bullet would tumble (it was minimally stabilized) when it hit something. The 12" twist was adopted early on because it was found that with the velocity drop caused by cold weather the M193 bullet was not stabilized, even marginally, out of the 14" twist barrel and inaccuracy was the result. The 7" twist was adopted to stabilize the long 5,56 tracer bullet used to give an 800 meter burnout in the M249 SAW. The M16A2 was adopted with that 7" twist also to stabilize the tracer bullet and the SS109 (M855) 62 gr bullet. The 9" twist stabilizes the 62 gr M855 but the 7" twist is needed for the tracer. Complaints are rampant from Soldiers and Marines from the Gulf War, Mogadishu and now the current war of the M855 being over stablized and "zipping" through enemy soldeirs without much effect. The Black hills Match ammuntion loaded with 77 gr Sierra MKs has been issued to many combat soldiers in Iraq and Afghanastan. It has been a proven better "stopper" due to better terminal effects of the MK bullet vs the M855 bullet. Thus the "never use match bullets" may not be entirely correct.

Larry Gibson

Addendum; unlike Bass, I do not hold such a high opinion of myself to think the professional ballisticians at Sierra or the others "from different companies to include old man Shilen" don't know what they are talking about.

[runfiverun]

having watched a few bullets fly through a spotting scope i learned long ago that you need to ignore what you see, or you will be watching the light being reflected back to you from something getting further away.
the light being reflected will be two feet away from where the bullet is actually at,and you better be looking for the impact not the streak.

and so far the consensus is that bullets/boolits can be over-spun.

some are saying that it is of little to no consequense, others are saying it has an effect
i believe that anything that upsets the bullet/boolit in any way is going to affect it's accuracy and performance on target. [regardless of it's intended target]
cramming it in the throat crooked,skidding, muzzle blast [pressure] and spinning it nose high or with wobble.
don't matter it is all= to ill effect on target.

[Pat I.]

R5R you've been the voice of reason throughout the last debate and now in this one. Kudos to you.

[Pat I.]

To change gears a bit. I've been thinking about something all day and if you don't mind I'd like an explanation from tiger and 44man or anyone else that wants to speak up since I'm looking for an answer. What do you think is happening out there during bullet flight that would make a 1 inch group at 100 yds turn into a 1/2 inch group at 2 or 300? A short explanation will do but if you want to throw some research in for me to look at that's ok too.

Just as an informational fact a 60 gr 22 cal bullet with a guessed at BC of .275 going 3800 fps will drift 11 1/2 inches in a 10 mile an hour crosswind at 350 yds according to my ballistic program if this pertains to your answer.

[44man]

Pat, you have to get the wind out of your hair. I gave you information for a test to do so you can see with your own eyes what is going on.
Get a good spotting scope and have someone shoot a S&W 29 with max 240 gr loads at long range. I won't tell you to try and see fast rifle bullets so the revolver has to do.
Now switch to 250 or 265 gr bullets and watch them.
You are so concerned with the wind, do it on a dead calm day.
I am 100% confident you will learn something and stop saying I am crazy.
I don't understand why some IHMSA shooters have not stepped in here, they watch bullets all the time.
You have heard the phrase that a bullet will "Go to sleep at long range." How about if you see it for yourself?

[Pat I.]

I've seen BPCR bullets in flight in different conditions but never experienced what your saying and a bullet "going to sleep" isn't the same as changing it's flight pattern. I need something else. Read what I posted above about a sleeping bullet being less effected by wind so it might lead to a smaller MOA at further distances but unless pushed back together by something it's impossible that the actual group size could be smaller.

If wind isn't a big deal how do you explain wind drift charts and software. I think if you watched a 240 gr bullet at 1300 fps you'd find the bullets are going to curve according to direction of the wind and not just because it's a natural phenomenon. Why wouldn't the same thing that makes a bullet naturally curve horizontally in flight not cause it to curve vertically upward once in a while? I know gravity's the answer but if bullets do crazy ass things why aren't they crazy enough to go up instead of down? Your 240 gr 44 cal bullet at 1300 fps has a drift of around 4 inches at 100 and 15 at 200 in a 10 mph crosswind wind so what you're seeing might be the affect of air on the bullet and not the bullet just taking a curved path because it wants to. I've got a test for you. Get a fairly windy day when the wind is switching back and forth and hold the same sight setting on the target while shooting when the wind's approaching from 3 oclock and then 9 oclock and watch the bullets. Dollars to donuts they'll start curving different according the the direction of the wind and string horizontally on the target.

According to your thinking "windage" adjustments on irons and scopes are only there for inititial adjustment.

[joeb33050]

Haven't seen much to change the chapter. For some reason this is a sore point with a lot of you, the RPM business. I don't know why. More theories and BS attach than any other topic I know of. Thanks to those who helped, there are enough of the others to form a nice tight circle.
joe b.

[44man]

Pat, the wind is not causing what we see. The over spun bullet will rotate like a corkscrew spiral around the intended flight path. It is not a large movement but it is very fast. It is NOT a yaw or direction change. It is NOT imbalance in the bullet because it doesn't run out of the flight path.
If the light is right so you can keep the bullet in sight for some distance, you will see this diminish, in other words, it is starting to "go to sleep."
You will see the effect of the wind as it curves the path, you also see the drop.
If you shoot a bullet spun just right so the spiral is not there, at the same target, right after, in the same conditions, both bullets have the same drift and impact the same POI down range.
The weird spin is not hurting anything other then to open groups at the closer ranges.
If it was possible to watch a very fast, highly spun rifle bullet, you would see the same thing.
I don't know how better to explain it, you HAVE to see it for yourself. A bullet going to sleep is a fact and is why a slower twist is better for close range target shooting FOR THE BULLET USED. Increasing the bullet weigh so it is slower or just reducing the velocity with the load can eliminate the effect with a faster twist.
Grossly over spinning a spitzer rifle bullet makes if more prone to tumble and veer off course when an animal is hit. Or a twig, blade of grass, anything between you and the target. A bullet can explode on a blade of grass and spray a target with schrapnel.
Grossly under spinning a bullet will make it veer off course in the air AND in game.
Shoot a BB and watch it! Shoot a round ball from a smooth bore musket and watch it. Do they go where aimed?
Now shoot a round ball from a 1 in 60 twist. Then try it from a 1 in 28 twist.
You need to match the bullet, twist and velocity for maximum accuracy and if you start to change any of these too far out of range, you will be disappointed.

[Pat I.]

What you're saying sounds like the effects of yaw and static bullet inbalances on a bullet's flight but doesn't explain how a bullet shot at 200 yds can look like it's going to hit the ram next door and suddenly do an about face and score on the one you're aiming at or how bullets that groups 1 inch at 100 decides to get back together and do 1/4 inch at 350.

The only way I can explain the "bullet shoots better farther out" thing as I see it is that you're saying a bullet's flight is in the shape of a blimp, pointed at both ends and fat in the middle. So eventually at some certain distance they should theoretically go through the same hole and then start opening up again. Is this right?

Joe, this isn't being derogatory but I think both sides of the argument have put out plenty of ideas both pro or con so what else are you looking for using the limited testing equipment anyone here's going to have? Searching the web on the subject will give you plenty of the hard facts you're looking for.

[44man]

Pat, the weird flight of the 30-30 boolit can't be explained. It is not the same thing and baffles all of us. It is not in a spiral but flies way off course and then swings back again. The shooter has to drastically change windage for each distance. Even then, I have been able to shoot nickels with this gun and boolit at 100 yd's. I can only assume it is on the ragged edge because I left off the gas checks once when I ran out and every single boolit went through the paper sideways at 50 yd's. (It was my gun until I sold it to my friend.) The association between twist, velocity and boolit is still there but we never figured it out. The TC has shot some impressive scores to 200 meters but it is with a constant windage change along with the normal elevation adjustment as range changes.
I can only say it will blow your mind watching it in flight. :mrgreen: We did not see it go up and down, just off to the right and back to the left.

As far as the spiral effect, no, once the bullet goes to sleep it will fly smooth and true and will not spread any more then distance changes minute of angle. Bullet holes in paper are perfectly round at every distance so there is no yaw to the bullet.
If you spin a top very fast, it will run smooth but walk around on the table in a circle. This is what we see but the walk around is MUCH faster. Once the velocity slows, the walk goes away. Spin slows less then velocity but I still think it still slows enough to stabilize the bullet. What you wind up with is a perfect match at 350 to 400 yd's that paper shooters want at the muzzle.
The .220 Swift I had was a BOMB. Hit a crow in a tree at 350 yd's and only the wings floated out of the tree. Starlings vaporized. Shoot a chuck in the head at 500 yd's and it looked like it was not hit but lift the scalp and the head was empty. Hit a blade of grass and the bullet exploded. Yet the bullet would bore a perfect hole through 1/2" cold rolled steel. More fun then anyone deserves! :drinks::drinks:
The Swift is outdated but I still say it is the very best varmint rifle ever! I carried three guns when chuck hunting. A Blackhawk .44 for up to 100 yd's, a Rem .222 for up to 300 and the Swift for anything over that. My pace is exactly 3' and through actual measurements, I was rarely off more then 1' at 100 yd's. We knew every field and chuck hole distance. Darn, I miss it all.
I had a Balver 24 on the Swift, easy to adjust the rear ring. I would sight at 350 yd's, then without moving, shoot another target set out every 50 yd's, clear to 600 yd's. The drop was recorded on paper taped to the scope. I also had the scope adjustment figures on the paper. I could hold over or click the ring to the right setting.
Here is the scope, what a piece of machinery!

[Bret4207]

Pat, the weird flight of the 30-30 boolit can't be explained. It is not the same thing and baffles all of us. It is not in a spiral but flies way off course and then swings back again. The shooter has to drastically change windage for each distance. Even then, I have been able to shoot nickels with this gun and boolit at 100

Huh? Please, take a crack at explaining. Are you sure you're not seeing something that's not there, like a shadow or reflection? Or is this based on paper results at various distances? If you're basing this on what you see through a scope I understand optical illusions can cause this to look like it's happening.

[leftiye]

Pat I,

Remember that the bullet's passage through the air is "wind" too. And it is many, many, many times (exponential increase in resistance with increase in velocity) more forceful than the wind that pushes a boolit to one side or the other on your target.

Do you think that aerodynamics has any effect on a boolit? You must as you above cite wind drift as a factor. Specifically, if a boolit is turned partially sideways by something (poor launch, rpm effect, deformed boolit, out of square base, etc.) that air resistance will deflect that boolit? Now, if that boolit rotates (nothing to do with centrifugal force) will it not change the direction of the deflection in a spiraling direction/manner?

When this instability (not to be confused with out of control instability) is overcome by true rpms (we spin boolits to stabilize them remember) will it not then stop flying in a spiral? If the original spiral was 1" in diameter at 100 yards, and the load is a 1/4" moa capable load, at 200 yards it will print 1/2" groups. Or, more likely 2' groups at 100 yds, and 1" groups at 200 yds.

Bullets, and boolits do "settle down" and there are other forces than centrifugal force that affect accuracy. These things don't just happen in theory. The groups are measured. The first time I heard of this was with a .375 Ackley imp. , the year was about 1975. I've had it hapen with my .375 H&H. McMillan saw it happen consistently with a complete lot of .50 cal barrels that he tested. And, yes the testing was done "on paper."

I would like to add my voice in applauding R5R's comment. Anything that affects accuracy will substantially bugger "best accuracy" and add to whatever happens at all levels of accuracy.

[Ricochet]

On occasion I've been able to see the paths of my bullets outlined by condensation, and was amazed to see how they followed a noticeably helical path. The size of the helix was big enough to account for quite a bit of dispersion at the target if the bullets were impacting at different points around the helix.

[Pat I.]

Leftiye I really don't understand what you're asking here. But to make it easier on both of us realize that the definition of deflection is to "curve something from a straight line or course" I don't know if this will help you ask your question in a better way but there it is.

Ricochet so does that mean you agree or disagree that bullets can shoot better groups, not MOA, downrange and curve into a target without the effects of wind?

[Ricochet]

I don't know. Hadn't given it much thought. I suppose that if the helical path straightens out as the bullet gyroscopically "goes to sleep" and follows the mean path of the helix, the angular dispersion might actually go down. Certainly don't have any data to back that up. I suspect that other factors like wind, convective turbulence and sighting errors that increase with distance might overshadow the improvement, if it exists.

[Pat I.]

Very diplomatic and I don't blame you :).

[Larry Gibson]

Let's assume every one is correct and the bullets do sometimes display a radius of gyration. Then let us consider "random dispersion" within the cone of fire. Is it possible that at some distance like the 350 yards for 44man or 200 yards instead of 100 yards that the bullets happen to be back in the same location in the cone of fire? If so then this provides a simple answer to why groups are smaller at some other range. The "helical path" mentioned by Ricochet or "radius of gyration" is real with some bullets that are over stabilized or under stabilized. I think we all agree on this as do all professional ballisticians.

We apparently agree that sometimes bullets that have a wobble and/or a radius of gyration can settle down at some point down range when the velocity and RPM match up to fully stabilize the bullet. If we believe that then is it possible that at some point of RPM the bullet may not "go to sleep" but instead the radius of gyration would get larger with increasing inaccuracy?

I have seen bullets switch directions from side to side on some ranges. However the effect was caused by the wind blowing from two different directions at different places down range. Several High Power ranges I've shot at are famous for this effect. However, for a bullet to move side to side on its own is something that would have to be explained to me. Never heard of such a thing in 30+ years of long range shooting. If it were real I think it would have been discussed in journals, articles and books dedicated to long range shooting. The radius of gyration effect is well documented and known. The effects of wind are well documented and known. The effects of air resistance to the bullet (stabilized or not) are documented and well known. This is the first I've heard of bullets "going off to the right and back to the left" without the wind being the cause.

Larry Gibson

[Bret4207]

FWIW- "Cone of fire" is a good description for what I'm visualizing. I'd just like to know if thats what 44 was describing or if we're talking the bullet zipping about in a random pattern and then returning to it's original path.

[Bass Ackward]

These discussions are really kinda funny. I did what I was asked and I got hammered for it.

I did a test with a factory slug, the 311291 that didn't fit my gun under certain criteria defined by others. Those criteria was defined as: meet or beat zone accuracy level with a high RPM load. Then tell a new shooter why he has problems with factory molds.

I did that at 165,000 rpm that met or bested the accuracy of the "classic load" by Mr Harrison. Part II was to define what a new shooter should be told if they asked why "they" have accuracy problems with a 311291. I did that also.

While my conclusions maybe not ideal, those steps sure gives a new shooter an idea what needs to be corrected better than just telling them .... RPMs baby.

Still I am the bad guy. I thought for sure I was going to get an atta boy. :bigsmyl2:

Everything else in the shooting world has been accepted as conquered except for HV cast. Nothing is more difficult. No one challenges any other claims on this board. In fact, accuracy claims if they occur in any zone are met with positive re-enforcement and encouragement to continue. Once the velocity figures have the first digit changed to a " 2", the stakes go up and out come the cries for at least 300 , 5000 shot groups. :grin:

The numbers of successful HV shooters simply aren't there yet. Although they are far higher than what the RPM crowd believe. As a result, HV as a positive topic of discussion may NEVER be viable on this board without the negative baggage it drags along. And those doing it say let them learn on their own.

I have been told privately that if I had a brain in my head, I would accept the reality of board opinion on HV as a subject. Makes perfect sense to me .... if all or most board members ever gave it.

Now I have some advice. RPMs is the "Perfect" theory really. Just raise your top numbers so it comes true again. As it is defined, eventually the numbers will reach levels no one can beat. That won't make it true, just not able to be dis-proven.

Until next time. :bigsmyl2:

[Larry Gibson]

Leftiye

"When this instability (not to be confused with out of control instability) is overcome by true rpms (we spin boolits to stabilize them remember) will it not then stop flying in a spiral?"

Only if the axial center gravity coincides with the center of form. If those two are not concentric the bullet still has static imbalance (it is still flying point forward) and still will have a radius of gyration. The formula to compute; deviation angle = arctan (2e*Pi/T). e is the radius of gyration and T is the twist rate. With the imbalances of Cast bullets caused during casting, sizing, applying Gc, etc and during acceleration the it is very rare that the axial center of gravity coincides with the center of form. This causes the dispersion of shots into the "cone of fire", i. e. what we call a "group".

Larry Gibson

[45 2.1]

These discussions are really kinda funny. I did what I was asked and I got hammered for it.

I did a test with a factory slug, the 311291 that didn't fit my gun under certain criteria defined by others. Those criteria was defined as: meet or beat zone accuracy level with a high RPM load. Then tell a new shooter why he has problems with factory molds.

I did that at 165,000 rpm that met or bested the accuracy of the "classic load" by Mr Harrison. Part II was to define what a new shooter should be told if they asked why "they" have accuracy problems with a 311291. I did that also.

While my conclusions maybe not ideal, those steps sure gives a new shooter an idea what needs to be corrected better than just telling them .... RPMs baby.

Still I am the bad guy. I thought for sure I was going to get an atta boy. :bigsmyl2:

Everything else in the shooting world has been accepted as conquered except for HV cast. Nothing is more difficult. No one challenges any other claims on this board. In fact, accuracy claims if they occur in any zone are met with positive re-enforcement and encouragement to continue. Once the velocity figures have the first digit changed to a " 2", the stakes go up and out come the cries for at least 300 , 5000 shot groups. :grin:

The numbers of successful HV shooters simply aren't there yet. Although they are far higher than what the RPM crowd believe. As a result, HV as a positive topic of discussion may NEVER be viable on this board without the negative baggage it drags along. And those doing it say let them learn on their own.

I have been told privately that if I had a brain in my head, I would accept the reality of board opinion on HV as a subject. Makes perfect sense to me .... if all or most board members ever gave it.

Now I have some advice. RPMs is the "Perfect" theory really. Just raise your top numbers so it comes true again. As it is defined, eventually the numbers will reach levels no one can beat. That won't make it true, just not able to be dis-proven.

Until next time. :bigsmyl2:

That hits the situation squarely on the head. Good job John.......
If you all want to know about funny rifles, ask McMillan (Sp) about Enfields and match shooting around 1400 yds.

[leftiye]

Right on Bass.

Larry????????? (not to sure why you posted that last)

[44man]

Well fellas, that 30-30 boolit did the same thing all year under every wind condition and even when it was dead calm. All three of us spotters reported the same thing. The boolit was very easy to see and follow until distance lost it. No shadows.
Yes wind from the side needed hold off, but the boolit still did the same goofy flight path. It did not matter what side the wind was from.
It will forever be a mystery. I never seen any thing like it after watching thousands of boolits, bullets go down range.
The very first time I seen it, I yanked my eye from the scope and asked Karl where the hell are you shooting? Then his ram fell.
Don't ever ask me to explain it. But it was consistent.
Bret, no, the scenes I have described are two completely different happenings. The .44 bullet doing the spiral did not appear like it was rotating around the nose, the whole bullet was moving around the flight path. I watched hundreds of them and forgot to watch the target most of the time I was so engrossed with it.

[Larry Gibson]

Larry????????? (not to sure why you posted that last)

Notice the question mark at the end of your sentence I quoted.....I answered your question.

Here, let me post your question again; "When this instability (not to be confused with out of control instability) is overcome by true rpms (we spin boolits to stabilize them remember) will it not then stop flying in a spiral?"

See, you asked a question is why. That's not to hard to figure out is it? (That's a question BTW)

Larry Gibson

[Pat I.]

Well since what up to this point has been a relatively peaceful conversation will more than likely turn into a mud slinging festival now I'm done here.

[Larry Gibson]

I'm backin' out now too. Was a good discussion we had going and were learning things. There's always some anomolies and perhaps that's what 44man ran across. Seems to defy what we all thought would happen out there. Sometimes things happen that are difficult to explian.

Not sure what brought Bass' post on but it sure turned this thread south. Too bad.

Larry Gibson

[Cap'n Morgan]

If the light is right so you can keep the bullet in sight for some distance, you will see this diminish, in other words, it is starting to "go to sleep."

I believe the spiraling and shifting of the bullets is appearing MUCH worse than it really is. This is due to the magnifying effect of the spotting scope "flattening" the image. As the bullet nears the target this zoom effect becomes less apparent, and the bullet seems to "go to sleep".

I've seen extreme zoom footage of chopper launched missiles where the missiles seems to almost spiral out of camera view, even when the helix cone of the missile path is probably only a few feet.

[Bret4207]

These discussions are really kinda funny. I did what I was asked and I got hammered for it.

I did a test with a factory slug, the 311291 that didn't fit my gun under certain criteria defined by others. Those criteria was defined as: meet or beat zone accuracy level with a high RPM load. Then tell a new shooter why he has problems with factory molds.

I did that at 165,000 rpm that met or bested the accuracy of the "classic load" by Mr Harrison. Part II was to define what a new shooter should be told if they asked why "they" have accuracy problems with a 311291. I did that also.

While my conclusions maybe not ideal, those steps sure gives a new shooter an idea what needs to be corrected better than just telling them .... RPMs baby.

Still I am the bad guy. I thought for sure I was going to get an atta boy. :bigsmyl2:

Everything else in the shooting world has been accepted as conquered except for HV cast. Nothing is more difficult. No one challenges any other claims on this board. In fact, accuracy claims if they occur in any zone are met with positive re-enforcement and encouragement to continue. Once the velocity figures have the first digit changed to a " 2", the stakes go up and out come the cries for at least 300 , 5000 shot groups. :grin:

The numbers of successful HV shooters simply aren't there yet. Although they are far higher than what the RPM crowd believe. As a result, HV as a positive topic of discussion may NEVER be viable on this board without the negative baggage it drags along. And those doing it say let them learn on their own.

I have been told privately that if I had a brain in my head, I would accept the reality of board opinion on HV as a subject. Makes perfect sense to me .... if all or most board members ever gave it.

Now I have some advice. RPMs is the "Perfect" theory really. Just raise your top numbers so it comes true again. As it is defined, eventually the numbers will reach levels no one can beat. That won't make it true, just not able to be dis-proven.

Until next time. :bigsmyl2:

Bass- I don't think there's any limit to what we might accomplish someday. It's just figuring things out and waiting for technology to help us. Back in the day of Townsend Whelen and Ned Roberts "gilt edge" accuracy might have been a Hornet shooting 1.75" groups, repeatably, at 100 yards. Or a 30-40 Krag shooting 2.5" all day long. There's no telling where we'll end up someday, so don't get discouraged. Same goes for Larry and the rest of the crew. We'll know who's right someday. For now we can just agree to disagree.

[44man]

No mud slinging at all, everyone has valid ideas and all of you have been very composed. I can only report what we have seen, some things can be explained and some just defy logic. Like leaving the check off the 30-30 boolit and having all of them go through a 50 yd target sideways. Makes a guy sit up and take notice real fast.
All of you have been great but these are still things that you actually have to see for yourself.