KIlling/Stopping Power From Twist Rate??

Great info, Ackleyman!

The practical experience is what is so interesting in this.
For the most part, I glean that indeed a faster twist rate does make a differece you can see. /ubbthreads/images/graemlins/grinning-smiley-003.gif

Thanks!
 
One thing to note though - I think your experience with the 90's in your .25-06 was a demonstration of bullet construction not being strong enough for a velocity level and a certain target density or mass. As opposed to an example of faster twist type bullet disruption.

In other words, back off the velocity a few hundred fps and that bullet would have performed fine. An example of this would be my .20-250 vs. a .204 Ruger. There are some bullets that perform superbly on coyotes at .204 Ruger velocities. But bump them up another 400-500 fps or so to the levels I'm launching them in my .20-250, and those bullets get no penetration, producing very large diameter, very shallow entrance wounds and poor killing performance instead.

Results of bullet construction being too light for a velocity/target are often similar to what you see with a faster twist, but the root cause is somewhat different.

And, by the way, velocity does not have nearly the effect on bullet RPM that twist rate does. It takes a LOT of velocity difference to cause the same change in bullet spin rate that a SMALL change in twist rate does. And the typical RPM of a bullet is much, MUCH higher than has been talked about in this thread. For a 9 twist barrel and a bullet at 3000 fps, the bullet will be spinning at 240,000 RPM. Slow the twist slightly, to a 10 twist, still at 3000 fps and you get 216,000 RPM. To get back to 240,000 RPM in the 10 twist, you would have to increase velocity by about 300 fps to 3300.

- DAA
 
50% deader.....

I don't know if you guy remember when Winchester introduced the Black Talon RIFLE bullets. They had to introduce a bullet for all 30 calibers and later introduced a 30-06/308 velocity bullet after they found out their initial assumptions were flawed. The first bullet introduced was made for a 300 Win Mag. They believed it would work for 30-06 because of the down range testing when shot out of a 300 mag: the velocity was the same therefore the results should be the same. What they found out was because they did not factor in the twist differences of the bullet being fired out of a 30-06 versus the downrange twist rate fired out of a 300 mag. the 300 bullet would not reliable work when fired out of a 30-06/308.

Long story, but it does show that twist rate does effect bullet performance. Velocity and rotational forces and target media all effect the performance of the bullet.

Aaron
 
So, will a bullet of the same weight and loaded with an identical powder charge, hit "harder" in a faster twist rifle? For example, a 55 gr bullet is more "lethal" in a 1-in-8 twist .223 than in a 1-in-12 twist .223? /ubbthreads/images/graemlins/confused1.gif
 
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So, will a bullet of the same weight and loaded with an identical powder charge, hit "harder" in a faster twist rifle? For example, a 55 gr bullet is more "lethal" in a 1-in-8 twist .223 than in a 1-in-12 twist .223? /ubbthreads/images/graemlins/confused1.gif



Isn't that the same question this thread began with, which has already been answered in detail? If not, I totally misunderstood the original question.

- DAA
 
There is a cost for shooting fast twists. The faster the twist, the longer the heat/pressure is maintained over a period of time.

No there was no doubt that I saw fire cracking sooner with land errosion sooner in my 9" twist hart in 22 PPC and 223 vs the 14" twists of the same.

The answer is easy, the heat with extreme pressure stays in the barrel longer in the fast twist barrels.

I had an 8" twist Hart barrel on a 6 PPC on a competition Benchrest rifle...hard to believe how much faster that barrel erroded compared to the same in a 13" and 14" twist.
The slower heavier bullets take more heat/pressure to get them started into the lands, and stay in the barrel longer due to slower velocities.

We were shooting 650-1000 rounds of centerfire a day on dog towns then, and it did not take long to figure out what's what.

Pick your poison.
 
ackleyman,
Have you tried any gain-twist barrels? I know they are usually more expensive, I do not know if they are less accurate than a conventional barrel.

I have read that faster twist rifling becomes bullet-jacket fouled more quickly than slower rifling twists.

Karl in Phoenix
 
Keith, that is all true. But then you need to add on top of that, the fact that because the faster twist results in a faster spinning bullet, all the effects of the alligator hide throat are magnified. It doesn't take too much of a rough throat to have jackets start coming apart when they are spinning at over 300,000 RPM. That's assuming using "short" bullets normally associated with slow twists. Add on to all that the delicate, finicky nature of long VLD type bullets and you've got a recipe for very short barrel life! My 8 twist .22-250AI only lasted 700 rounds. The throat looked bad, but not as bad as my 12 twist .22-250AI that has 1500 rounds through it. But the 12 twist is still going strong, no "poofs" yet. But then, those bullets are only doing 225,000 RPM, even though they are being launched about 500 fps faster than the long heavy 80's were from my 8 twist.

- DAA
 
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So, will a bullet of the same weight and loaded with an identical powder charge, hit "harder" in a faster twist rifle? For example, a 55 gr bullet is more "lethal" in a 1-in-8 twist .223 than in a 1-in-12 twist .223? /ubbthreads/images/graemlins/confused1.gif



I would say "maybe".

If it's a coyote, it might be less "lethal", because all the energy is expended instantly on the surface, and the yote might run.

But on a target that does not need deep penetration.. crows, PDs, and ground hogs... I would say definitely YES!
 
Funny how just 3 months ago (June) we discussed the same topic here about terminal performance of varmint bullets compared to different twist rates... And there were a bunch of "experts" who claimed that twist rate has NO effect on terminal permormance. Here is the thread, and here are some of the quotes from that thread:

http://www.predatormastersforums.com/ubb...part=1&vc=1

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The difference in twist will show NO appreciable difference in terminal performance.



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Don't think you're comprehending what we're saying. The twist has NOTHING to do with fur damage.


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I have never seen, nor heard of an appreciable difference in any damage as far as wound chnnel from differeces in twist rate.



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With a 1-8 twist the bullet will turn about 1/4 turn going thru a ground squirrel and a 1-12 about 1/6 turn on same critter so I can't see any more damage.



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Bear you are exactly correct. Once before on this site I calculated the difference in imparted energy....even if you assume complete rotational transfer, the difference between a 1/12 and 1/9 twist with a 55gr. bullet out of a .223 is less than .2% of the energy transferred. You are MUCH more likely to see rapid expansion from rough barrels than a slightly faster twist.



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I also think that an inch of barrel length would put WAY more difference on the same cartridge than any rate of twist could do. I'm talking "practical" hunting here with this.



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My opinion, only....The difference 50 fps would make in the bullet would be FAR more drastic on the terminal performance than any rate of twist.



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You may rationalize and conjecture by simple analogy all day long. What I am saying is that in hundreds of gel shots we have not noticed a statistical difference (in wound channel width or depth) between identical bullets fired at similar velocities at multiple twist rates. Not with varmint bullets...Not with FMJ...Not with traditional hunting bullets...To be quite honest we were trying to prove the opposite to use as a sales gimmick.




I don't see those people defending their theories now that the real experts have added their wisdom...
 
Stiff neck: You have a great memory. Well done.

Barrel rifling twist rate does provide changes in terminal effects, if the bullet weight and velocity are held constant.

Expanding bullets tend to "upset" more rapidly at faster twist rates (other variables held constant), due largely from higher centrifugal forces tending to pull the bullets apart.

Karl in Phoenix
 
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Funny how just 3 months ago (June) we discussed the same topic here about terminal performance of varmint bullets compared to different twist rates... And there were a bunch of "experts" who claimed that twist rate has NO effect on terminal permormance. Here is the thread, and here are some of the quotes from that thread:



I don't see those people defending their theories now that the real experts have added their wisdom...



The thread was about whether 40 grain bullets could be shot out of fast twist barrels (yes), but drifted into the damage issues.

I was not part of that thread... but several of the people DID say that faster twist (with the same bullet) DOES cause more damage.

Here's the thing.

When this subject comes up, many will quote other bullets or other dynamics, to prove their point. The Black Talon has nothing to do with this - it is a heavy bullet traveling at ~1,000 fps.

And several people claimed that it does not make any difference how fast a bullet spins because it makes the same size hole through the critter.

All are not relevant, because we are not speaking about bullets that stay together through the critter... we are talking about bullets that fragment in the animal.

When varmint bullets are spun out of a barrel, there is a lot of force locked up in that spin, and that force want to tear the bullet apart even BEFORE the bullet hits anything.

You guys that have been shooting a while have seen cases where bullets like the SPSX and Blitz just plain fly apart before reaching the target when spun at much over 245,000 rpm, regardless of the twist - the faster the twist, the slower you have to shoot them, or they will fly apart.

These varmint bullets have a 9 mil jacket (nine thousandths of an inch thick), and they are ready to fly apart at the slightest provocation.

The SPSX and the Blitz bullets are ideal for the 222/223 family with 14" twist, because they are so fragile.

The companies make similar soft point bullets with a 20 to 22 mil jacket. These are good for the faster cartridges and/or the faster twists.

But with the plastic tipped bullets like the BlitzKing and the V-Max... these can withstand the high rpms of fast twist barrels, but when they hit, the plastic wedge starts them coming apart fast - they don't expand and "mushroom", they shatter and fragment like a broken glass.

Now... with two identical bullets are moving forwards, and spinning at different rates - and both shatter... the faster spinning bullet will have a wider cone of fragmentation.

This wider cone will cause more damage in the earlier stages of penetration. In a PD, ground hog or a Squeek, it will make the difference between the critter falling over, or coming apart and going skyward.

None of this applies to bullets that don't fragment fairly fast.


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So, will a bullet of the same weight and loaded with an identical powder charge, hit "harder" in a faster twist rifle? For example, a 55 gr bullet is more "lethal" in a 1-in-8 twist .223 than in a 1-in-12 twist .223? /ubbthreads/images/graemlins/confused1.gif



I would say "maybe".If it's a coyote, it might be less "lethal", because all the energy is expended instantly on the surface, and the yote might run. But on a target that does not need deep penetration.. crows, PDs, and ground hogs... I would say definitely YES!



Thanks, CatShooter. Thats what I was driving at.
 
DAA, I totally agree with everything you have said!

I am a firm believer to shoot the slowest twist to stabalize the bullet you intend to shoot!

I had a whale of a time maintaining 1/4" accuracy (or less)day in and day out in the 9" twist 223 and 22 ppc, and the 8" 6 PPC. Suttle changes in weather seemed to make more of a difference in the pressure curve in the faster twists.

For that reason, I am not a fast twist man.
 
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So, will a bullet of the same weight and loaded with an identical powder charge, hit "harder" in a faster twist rifle? For example, a 55 gr bullet is more "lethal" in a 1-in-8 twist .223 than in a 1-in-12 twist .223? /ubbthreads/images/graemlins/confused1.gif



I would say "maybe".If it's a coyote, it might be less "lethal", because all the energy is expended instantly on the surface, and the yote might run. But on a target that does not need deep penetration.. crows, PDs, and ground hogs... I would say definitely YES!



Thanks, CatShooter. Thats what I was driving at.



CV32, Catshooter beat me to it! But the answer to that question is "It depends on the density of the target" The higher the density of the target= diminishing returns. Once the structural integrity of the jacket has been compromised the faster and more violently the fragmentation of the projectile becomes, therefore reducing the penetration. But on a prairie poodle you don't need much penetration, on a coyote you need a little penetration which would explain what was mentioned earlier about slower rounds being a more efficient killer of Cape Buffalo being that you need so much penetration to be effective.

On a side note, Catshooter...... I liked you better when we didn't agree on so much /ubbthreads/images/graemlins/tongue.gif

Chupa
 
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"...On a side note, Catshooter...... I liked you better when we didn't agree on so much /ubbthreads/images/graemlins/tongue.gif

Chupa



Yeah... I know.

I try, but sometimes I fall behind. /ubbthreads/images/graemlins/smile.gif /ubbthreads/images/graemlins/smile.gif /ubbthreads/images/graemlins/smile.gif.


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Remembrances of that older thread combined with new conversations about the same thing is what prompted me to start this new thread...

It is interesting how quickly this subject has picked up steam in the varmint/predator hunting world.

Especially with the newer rifle barrels coming with faster twist rates.
 
Question - When using a fast wist barrel, does the bullet stay in the barrel a longer amount of time versus a slow twist barrel?

The length of the barrel would be the same (26" as an example) but does it take MORE time for a bullet to exit a fast twist barrel than a slow twist barrel?
 
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Question - When using a fast wist barrel, does the bullet stay in the barrel a longer amount of time versus a slow twist barrel?

The length of the barrel would be the same (26" as an example) but does it take MORE time for a bullet to exit a fast twist barrel than a slow twist barrel?


Probably no measureable difference. But, fast twist barrels are used to shot heavier bullets which probably do take a tiny bit longer to clear the barrel.

Jack
 
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Question - When using a fast wist barrel, does the bullet stay in the barrel a longer amount of time versus a slow twist barrel?

The length of the barrel would be the same (26" as an example) but does it take MORE time for a bullet to exit a fast twist barrel than a slow twist barrel?



Fast twist barrels, when used with heavier bullets, have shorter life, because the time in the barrel is longer, and the peak temperature curve is longer.

If you shoot light weight bullets, the barrel life is the same.


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