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Posted: 10/15/2004 7:10:31 PM EST
[Last Edit: 10/15/2004 8:08:12 PM EST by wyv3rn]
Ok, I know most of you visiting this thread are already hot on the reply button. I would be too because I already know the old answers to this question. Now I would like to discuss this further.

The answer to this question since I first started studying terminal ballistics has been a resounding "no" and until proven otherwise, I agree. But recent tests and information has revealed that the angle of the bullet at the time of impact can effect how quickly the bullet yaws inside the target after entering it.

We all know that the earliest yaw possible is desireable and more effective than a late yaw cycle. One reason is the location of vitals within a human target. But I have to wonder if there is another reason.. from the time a bullet hits a target it decelerates rapidly. It is my unfounded/unproven but reasonable guess that the earlier it yaws and fragments the higher the stresses on the yawing bullet and the more reliable and violent the fragmentation.

So I have to wonder if rifle twist rate does (or can be made to?) effect the angle of impact. And if so, is anything sacraficed (such as accuracy)?

1. It has been suggested that a much tighter twist than optimal (such as 52gr in a 1/7) could cause a bullet to travel nose-up for long distances before "settling in". Wouldn't this be desireable from a terminal effects standpoint? Does this hurt accuracy? Could you do the same thing with 68/69gr or 77gr w/ a 1/3 twist or something like that?

2. Now, I know that bullets that are not stabilized will travel very wobbly, possibly tumbling, hence the keyhole on your target. And while this might be very terminally effective with the right bullets, you're not going to be able to put any kind of accurate fire on distant targets. But what about using such a rifle/carbine for CQB out to maybe 75 yards? Wouldn't this have improved terminal effects or atleast make good terminal effects more reliable? You certainly don't have to wonder if your bullet is going to yaw inside the target or travel in and out without yawing. Another side benefit would be that it would be more likely to break up against barriers and not overpenetrate. If the bullet were to escape the building it would loose velocity more rapidly, not travel as far and slide below the fragmentation floor sooner than a bullet that is properly stabilized.

Or are these ideas completely absurd?

Edited to add: What about making an unbalanced bullet itself that would wobble after leaving the barrel? I doubt it would be accurate enough to use past 75 yards but CQB?
Link Posted: 10/16/2004 5:34:00 AM EST
Just for clarification, can you define what you mean by "nose up?"

If it's what I think it means, you're talking about an overstabilized bullet's nose not following its arc path, but rather pointing at the same angle to the ground as when it left the barrel. Are we talking about the same thing?

Link Posted: 10/16/2004 6:16:43 AM EST
You're thinking way too hard, Jethro. Just go shooting.
Link Posted: 10/16/2004 10:23:54 AM EST

Originally Posted By leakycow:
Just for clarification, can you define what you mean by "nose up?"

If it's what I think it means, you're talking about an overstabilized bullet's nose not following its arc path, but rather pointing at the same angle to the ground as when it left the barrel. Are we talking about the same thing?




Probably, I don't know the physics or details behind overstabilization. My impression of what is happening when a bullet is overstabilized might be completely wrong. I've only read a brief paragraph or two on it.
Link Posted: 10/16/2004 12:50:24 PM EST
A related concern might be whether the twist rate influences the muzzle velocity to any significant degree. The faster twist should generate higher pressures, how that effects the speed of the bullet itself I have no clue.

Feamster reported noting that some bullets were apparently deformed by the PRESSURES generated from some of his hotter loads, and their bc went down, as well as deteriorating the accuracy.

Your post was concerning the TERMINAL ballistics. I suggest that you can't divorce the potential velocity variations attributed to twist rate changes from the consideration as well, since the terminal effects will be dependant upon the velocity.

There is a 100 foot long mudhole between me and my local range at present, but I can clock some Q3131A, etc. from 1/12, 1/9, and 1/7 twists later and see if there is any statistically significant trend shown.

Paladin
Link Posted: 10/16/2004 1:14:33 PM EST
Link Posted: 10/17/2004 3:25:47 PM EST
[Last Edit: 10/17/2004 3:29:00 PM EST by wyv3rn]

Originally Posted By Tweak:

Originally Posted By markm:
You're thinking way too hard, Jethro. Just go shooting.



+1



Am I the only one laughing about this reaction?

Throughout our history, scientists -- both ameture and professional pose a question, and they receive this kind of reaction. Even more ironic is that it comes from people who supposedly embrace the scientific method and use the technologies it produces every day. Well sorry guys, the questions always have to be asked/discussed before progress can take place.

Yes, the idea seems ridiculous on the surface. In all the years the rifle has been the weapon of choice I don't think anyone has ever asked for a rifle that doesn't stabilize a bullet in flight properly.

Yes the idea is unconventional and in the end may prove unuseful as well but I haven't seen the question posed. I don't see what's wrong with trying to eak out a little extra terminal performance at no real dollar or upgrade cost, only effective range. It would have it's niche roll just like many other weapons that have been used successfully in the past.

Hell, I KNOW 99% of you already believe the 10.5" AR carbine is a niche weapon. What's wrong with trying to make it more effective at no $ cost?

I'm not afraid to ask a question that may seem "silly" and I've never been and never will be intimidated by close-minded nay-sayers. I've been wrong before and I've been right before, but what's most important to me is that I'll always be willing to ask the question and not worry about egos or spoiling reputations. I don't let my pride get in the way of "making an ass" of myself if there is potential payoff. I'm asking those of you who are not interested in constructive conversation refrain from posting to this thread.
Link Posted: 10/17/2004 3:34:28 PM EST

Originally Posted By PALADIN-hgwt:
A related concern might be whether the twist rate influences the muzzle velocity to any significant degree. The faster twist should generate higher pressures, how that effects the speed of the bullet itself I have no clue.

Feamster reported noting that some bullets were apparently deformed by the PRESSURES generated from some of his hotter loads, and their bc went down, as well as deteriorating the accuracy.

Your post was concerning the TERMINAL ballistics. I suggest that you can't divorce the potential velocity variations attributed to twist rate changes from the consideration as well, since the terminal effects will be dependant upon the velocity.

There is a 100 foot long mudhole between me and my local range at present, but I can clock some Q3131A, etc. from 1/12, 1/9, and 1/7 twists later and see if there is any statistically significant trend shown.

Paladin



I've seen tests on twist rates' effect on bullet velocity. From what I saw there was no significant deviance or correlation between bullet muzzle velocity and twist rate.
Link Posted: 10/17/2004 5:54:58 PM EST
The angles you are talking about matter a thousand times less then the angle or movement of the target therefore you will have NO noticable difference in terminal ballistics. For example you could not say "After inspecting the body it is clear this man was hit with an over stabilised projectile due to the length of neck before fragmentation" because there is more variablity from bullet to bullet than there is in the difference of .1 degree angle of off center impact. The guys mocvement on impact, like running vs walking has much more of an influance that what you describe. We are only talking about shots at 150m or so max as thats the limit of most ammo to fragment anyway... therefore the bullet will not be off angle from its flight vector by any significant degree. When things are so inconsequential you cannot measure them they dont matter. Twist rate DOES NOT MATTER in this sense unles your bullets are keyholing from shooting your 75s in a 1:12 barrel or something silly like that.
Link Posted: 10/17/2004 6:35:45 PM EST


Interesting question.

Let's examine a few "knowns" and then try to extrapolate some possibilities.

We observe with the .223 round that it has a minimum effective velocity below which destabilization and fragmentation will not occur upon penetration into a target.

This destabilization is caused when the bullet experiences a change of medium - that is, when transitioning from the medium of air to the medium of flesh.

The higher the velocity, the more likely the bullet will destabilize.

The lower the velocity, the less likely the bullet is to destabilize.

We also know that the faster the twist rate of the barrel, the faster the bullet will rotate when it leaves the muzzle.

For a hypothetical bullet travelling at 3,000 feet per second, it would rotate at 5,143 revolutions per second or 308,580 revolutions per minute in a 1:7 twist barrel, and only 4,000 revolutions per second or 240,000 revolutions per minute in a 1:9 twist barrel.

Now for the conjecture.

Maybe if faster velocity means better bullet destabilization upon impact, then higher rotational speed may also result in better bullet destabilization upon impact.

If so, then the effective range of any given bullet/barrel combination could be extended by using a faster twist barrel. In other words, as long as the bullet is stabilized by the barrel, then the faster the twist the better - 1:7 would be better than 1:9.

BTW: I'm not covinced that "overstabilization" is real. I do believe that if one shoots 40gr varmint bullets out of a 1:7 twist barrel that the bullet may self destruct due to over rotation, but any bullet used in a defensive scenario (i.e. 55gr and above) shoots just fine in a 1:7 barrel.

Stream of consciousness mode OFF.
Link Posted: 10/17/2004 9:42:10 PM EST
Your way off... all bullets destabilise and only fragment due to the forces induced by velocity so your whole post is BS.
Link Posted: 10/17/2004 9:45:49 PM EST
"would you care to take off your pocket protector and step outside for a beating"
Link Posted: 10/17/2004 10:13:19 PM EST
Link Posted: 10/18/2004 9:19:59 AM EST

Originally Posted By Tweak:

Originally Posted By wyv3rn:
I'm asking those of you who are not interested in constructive conversation refrain from posting to this thread.



You want "constructive conversation"? OK, this topic has previously been done to death by people who know next to nothing about ballistics, you will note that none of the Mods in the forum have posted here, most likely because they are tired of answering the same questions over and over again.



I too have seen it discussed many times by people who know nothing about ballistics. That's why I'd like to see it discussed by people who do know ballistics. Especially that it seems that testing criteria are now going to place a higher emphasis than previous on measuring angle of impact.

www.dtic.mil/ndia/2004arms/session9/minisi.ppt


You want effective ammunition?

LEARN TO HIT THE FREAKING TARGET!



DUH! For ANY ammunition to be effective it must be on target. Does anyone NOT know this? You must hang around in different circles than I, because almost every shooter I know already knows this. Most of us happen to hit the target just fine thank you.

Don't try telling me that a .22LR is as good as a 7.62x51mm. Why is everyone excited about 6.8SPC? Because you're eeking more performance from generally the same package.

I never said this is the new panacea for short range firefights. I simply asked for a reasonable discussion from those "in the know" about how twist rate could possibly be harnessed to create a more effective package at no cost, in light of new information.

Early yaw and dramatic fragmentation are important. This is obvious to anyone who has read anything in recent terminal ballistic studies. It is the reason the 6.8SPC OTM 115gr has a hollow cavity in it's tip beyond that created by the match bullet forming process. All I am doing is soliciting discussion of ways we can harness and apply this to current weapon systems at no cost and I am open to all methods until they are disproven.
Link Posted: 10/18/2004 10:53:51 AM EST
The mods are not discussing it because I already addressed it.
Link Posted: 10/18/2004 10:55:07 AM EST

Originally Posted By wyv3rn:
Or are these ideas completely absurd?



Yes.

And it is a dupe topic too. I thought I saved the one from last spring, but can't find it now. It had all the reasons twist rate did not change terminal effects all spelled out. Too bad the search function won't go go back that far.
Link Posted: 10/18/2004 10:25:16 PM EST
Link Posted: 10/19/2004 8:25:21 PM EST
Twist rate affects stability in air, not tissue. Velocity is far more important
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