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JPK, bear with me...

I'll look for it. Sounds very interesting. I'm still having a tough time seeing how a bullet that makes, say, 2.5 turns in 36 inches {1/14} of penetration could kill noticeably better than an identical bullet that makes 2 turns (1/18). Not saying it's impossible...

I agree pointed bullets are irrelevant to the discussion but I am referring to MKII and MKVI .303 bullets which are 215 grain RNFMJ's and known in military and hunting as deep, straight penetrators and discussed in TSA '29. No dice on terminal effect of various twist rates on the bullets in TSA '29. There are extensive discussions on twist rate {and many mathematical calculations beyond my ken} but they involve exterior ballistics for the most part. Poor overall killing power is noted on men with such bullets compared to lighter, pointed bullets. That is not so much due to yaw and tipping over of bullets as it is related to striking velocities and resultant hydraulic effect and energies imparted to secondary projectiles like bone, etc. Since the Great War {and SA War} was fresh on everybodies' minds this discussion is decisive. Most pointed .30-.323 military bullets tip in media after penetrating deeper than a torso shot on a man. None of this is particularly relevant to elephant hunting.

Having not read the material you reference yet, I cannot say, but one twist-rate factor that might effect terminal performance of heavy caliber, close "stopping" rifles is the distance required to make a bullet "go to sleep". All bullets exit the bore as "tippers" and take some distance to reach maximum stability, just like a top does when you give it a good "zing" and it wobbles and then spins true. This normally is exhibited in lessened ability to maintain straight penetration in dense mediums if impact occurs before max stability is reached.

Mmm... But does a quick twist take a few more yards to stabilize a bullet than does a slower {but adequate} twist or the other way around? I do not know.

On elephant it just might matter, and may explain strange bullet behavior on shots taken at real live life'n'death close ranges if strange behavior exists. Long-for-caliber monolithic solids may be effected more by such a phenomenon {bullet length dictates twist rate}.

There might be the twist rate mystery solved, but I'm not sure. Maybe the issue is twist rate as it impacts the actual distance necessary for the bullet to reach max stability BEFORE impact occurs. All bullets possess a certain amount of yaw before entering a target. It seems that in elephant hunting the minimization of preimpact yaw is maybe more important than is in any other hunting if for no reason than that the shots that truly matter may occur before this is reached in some rifles...

For testing softs, I can, based on my own testing, say with a fair degree of confidence that impact before max stability is reached does not materially effect performance of the bullet though some bullets tested recently indicate more "smear" on one side than another. Haven't explored that enough... Most sources seem to refer to 20 meters or so as being the closest distance a bullet takes to reach max stability and that is where I do my testing.

Regardless, if you introduce more yaw to one bullet than you do to another, penetration is very likely to be effected.

By the way, not sure what you mean by original twist rates of the M16. M193 is extremely stable when fired in standard 1/12 "A1" barrels. Dramatic wounding effect is primarily a result of fragmentation, not merely yaw of the bullet. M855 requires a 1/9 or so twist, the move to 1/7 in the A2 being made necessary by long tracer rounds only, which require a tighter pitch of 7.5-8 or so.

Now you make me want to sell the pickup and a horse or two and go elephant hunting...

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Edited by 9ThreeXFifty7 (31/12/08 01:18 AM)

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