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Does twist rate effect terminal performance?

To what degree, if any, does twist rate effect terminal performance of varmint bullets? I’ve heard it said that a bullet out of a faster twist will tend to blow apart on impact more so than a bullet out of slower twist barrel? Wouldn't that give a faster twist barrel more of an effective range on groundhogs than a slower twist of the same caliber?
 
That is the theory I've heard as well and it stands to reason. Take the Speer TNT. For my gun, Speer says 3500 fps max in a 10 twist or the bullet will disintegrate in flight. Since the jacket is already stressed close to failure a shot at 3400 fps should explode when the jacket integrity is compromised on penetration; provided the impact doesn't stop the rotation or slow it significantly.
 
So for instance say a 7 twist 223 can’t shoot a 55g Vmax because it’d blow up in flight. Would that make the most explosive bullet for a 7 twist 223 a 60g Vmax?

Or how about the other way? Say a 14 twist can’t stabilize a 60. Does that mean the 55g is most explosive because it’s right on the edge of instability?
 
In my experience, when shooting a 22 caliber, you need to go from a 14 twist to a 9 twist to see a difference in bullet performance.

In the 6mm, you will need to go from a 14-12 twist to an 8 twist to see a difference in bullet performance.

Now having said that, the tighter the twist, the more the pressure tends to spike given the same caliber and weight of bullet. The loads get very picky in fast twist barrels compared to a slower twist barrel.

I played around with an H-Bar shooting the 55g Sierra BTHP at 2950 fps compared to the same bullet shot out of a 14 twist 22/250 at 3550 and the H-Bar blew up dogs better.

Also, had a custom 9 Twist 223 on an AR frame and the loads that would shoot in the .280 range were very picky.

Next came a custom 22 PPC, match grade all the way with a Hart 9 Twist, minimum spec match chamber. I compared this to another 22 PPC with a Hart 14 twist barrel. The 9 twist was very accurate and VERY touchy on the 1/4" loads that it would shoot.

This is my experiments on fast twist, mid weight bullets in 22 calibers.

I put together a fast twist 6 PPC in 8 twist to shoot the Berger 105's...holy cow...talking about picky loads...jeez. It would shoot like a bandit, but you would have to tune the loads at every match a bunch!

Good luck in your quest!
 
If you have a specific bullet hitting an animal at a specific velocity and the bullets are both hitting stright, I doubt you will see much of a difference. If the bbl twist either nets more velocity or unstabilizes the bullet so that it doesn't hit stright,,keyhole) terminal performance will most likely differ.

Chris
 
I've had several experiences with bullets "blowing up" or "vaporizing" after leaving the barrel of 1:8 and 1:9 twist rifles. A 50-gr. .22 cal. bullet exiting a 1:9 twist barrel at 3,500 fps is rotating at about 290,000 rpm. If it is a TNT or SX type bullet with soft lead center and slits in the jacket, it cannot hold itself together and comes apart like shrapnel,and will wipe out a Chrony!!). If it does hold together for a bit, it is likely to "blow up" just going through the paper of a target or hitting any kind of resistance. The same loads in a 1:12 or 1:14 barrel show no signs of coming apart.

Some theories hold that the pure lead cores, at the forces and stress applied to them, may actually become molten, aggravating the "blow up" problem. A bullet that is on the verge of "coming apart at the seams" would likely show more, or at least quicker, explosive action on a target.

The use of faster,1:8) or slower,1:14) twists is mostly dependent on what size and speed of bullet you want to shoot. Usually light, short, fast bullets want the 1:14 and heavier, longer bullets will only work in the 1:8 or so twist. I don't think you will ever get best accuracy with a bullet that is on the edge of self-destruction.

We have the best-ever selection of bullets to choose from these days. There is a bullet available that will perform at whatever end of the spectrum you want. The TNTs and SXs are designed for fast expansion at moderate speeds. The rigs that will will push a bullet to 4,000 fps and beyond do not need soft lead and light jackets to be destructive.
 
But doesn’t a bullet hold its RPMs much better than its velocity? Isn’t that why a near max sized bullet that is stabilized at 100 yards is still most likely be stable at 500 yards? So when the bullet manufacturers put out info saying a bullets performance window on varmints is from, for example, 1500FPS to 3000FPS, aren’t they missing a very important ingredient? You can’t control the velocity of a varmint bullet to any great extent if your first target is 50 yards and the next is 700 yards. But if a certain bullet RPM,twist) will cause a bullet to be much more likely to fly apart on impact, well there’s a terminal performance consistency and a big ricochet safety factor that I want to be using. Even if it may be at the expensive of some of the bullet’s other characteristics.

ReedG, did you mean to say that you had bullets spinning so fast that just hitting a piece of paper made them blow apart? Did the target paper itself have a big hole?
 
Tripcrow,

Yes, RPM remains relatively constant at all ranges. The high rotational speed of hotrod .22 centerfires is the reason explosive hits are seen at distant ranges where the bullet velocity has dropped to .22 LR speeds. This very phenomenon is well-documented in P.O. Ackley's first volume. The chapter is titled 'Killing Power'. It's a real eye opener!

Tom
 

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