Intermediate Cartridge Wounding Profiles


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Skribs
November 28, 2012, 01:28 PM
I've long been an advocate of rifles for self defense, and plan on getting one in the future, because of how the rifle round does its wounding - with the cavitation trauma. However, I was looking again at the profiles at this link, and I noticed there are two real types of profile:

http://ammo.ar15.com/project/Self_Defense_Ammo_FAQ/index.htm#RIFLE%20AMMUNITION

Forgive me if there are technical terms, but there are the "poke" profile and the "balloon" profile. The poke wound tracts are long and narrow, with maybe slight humps where the bullet yawed, with a very wide temporary cavity. I'm not sure what the permanent cavitation trauma would be, but there is a very clear line where the bullet passed through.

The balloon wound tract is one where the bullet either initially or after going straight for a while, will expand or fragment, resulting in a balloon-shaped cavity. If the bullet had fragmented that cavity generally is the end of the tract; and if it expanded then the bullet will continue to pass through.

Now, my question here is sort of two-fold:
1) With a bullet designed to poke through the target, how much permanent cavitation trauma is there? Or is the bullet just zipping through without upsetting the tissue too much? (as a comparison, I noticed when I was a kid shooting cans with a BB gun that 1 pump would send the cans flying, but 10 pumps would have the BBs just pass through the cans as if the can had never been hit).

2) With a bullet designed to expand/fragment, I notice that there is either a set or random point at which the wound tract is widest, and at all other points it is fairly narrow. In the case of a bullet that balloons at 10", for example, a straight-on shot would have a narrow profile, but in the case of one that balloons immediately and then after 6" is just straight JHP penetration, a "worst-case" shot (i.e. through the arm and at an angle) would have the narrow point of the wound tract in the vitals.

I am asking this specifically from the context of self defense, but also from the perspective of someone trying to figure out what the best option is. My current situation is that I own pistols and shotguns, and have my eyes set on getting a rifle in the future. However, the reason I want a rifle is due to the impressive wound tract (I consider the rifle round's cavitation trauma to be the most efficient use of recoil, if this sentence makes sense), and if that wound tract is narrow at the vitals, then I might as well have picked a 9mm.

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eldon519
November 28, 2012, 01:49 PM
The think the idea with the expanding bullet is that 1) it gets bigger so it makes a bigger permanent crush channel and 2) it imparts more energy to the tissue it is traveling through as/after it expands. The energy imparted is basically a mechanical wave (similar to sound for instance) through the tissue and if enough energy is imparted and the amplitude is great enough, the tissue is stretched beyond its elastic limits and is damaged.

I think there is some magic velocity where there is enough energy imparted to the target rapidly enough to make the temporary cavity into a permanent wound. It makes sense though mathematically. Since kinetic energy is related to the square of velocity, the faster something is going, the more energy it would impart. A simplified example would be a "high speed" projectile going 10 fps that exits its target at 9fps and a "low speed" projectile going 5 fps that exits its target at 4 fps. If the projectiles were of the same mass, even though they both only slowed 1 fps when passing through their target, the high speed projectile would have imparted 9.5m units of energy (where m is mass) and the low speed projectile would have imparted 4.5m units of energy. The math is 0.5*m*(100-81) for the fast projectile and 0.5*m*(25-16) for the slow projectile. This just shows how something going faster imparts more energy as it slows. And energy is tied to amplitude in a mechanical wave, where amplitude is basically needed to stretch the tissue until damaged. How elastic the tissue is would determine how quickly you would need to impart the energy which I'm guessing is where the magic velocity number comes from.

I'm sure this is oversimplified and/or wrong, and I may have to don my flame suit, but that is my basic understanding.

heavydluxe
November 28, 2012, 02:23 PM
I have recently gotten really interested in external and terminal ballistics... I found this website helpful:
http://www.rathcoombe.net/sci-tech/ballistics/wounding.html

Skribs
November 28, 2012, 02:53 PM
Wow, heavy, I read/skimmed a good portion of that, looks interesting. However, I didn't see (or don't think I saw) an answer on my two questions. Although I guess...

1) Bullets which simply poke through and yaw it seems would have a fairly low meplat while yawing, despite the long length, because of the rounded nature of the bullet, but it would still transfer more energy than when the bullet is flying straight. I am curious though as to what the difference in size between temporary cavitation and permanent cavitation is (the easiest-to-read pictures I've seen just show cavitation vs. crush trauma).

2) While this site and Eldon's post both bring up the varying diameter at different penetration depths, I haven't seen a discussion on how it applies to stopping a human attacker with the understanding that the vitals will be located at varying depths as your angle on the target changes and/or the target's limbs come into play.

So, for the sake of argument, let's say the "balloon" is 3" at its widest, but prior to expanding the wound tract is 0.5" and after the energy has tapered down the bullet crushes a path 1" wide. The way I see it, you would want the balloon to hit in the vitals, so you're hitting the target with a 3" wound tract instead of 0.5-1". But if the bullet expands deep and you get a straight-on COM hit, the wound tract is going to be 0.5" wide through the vitals and start to expand in the exit wound. If you have to shoot at an odd angle, you might have a big messy hole before the vitals, and then a 1" hole through the vitals.

In both of these circumstances, the rifle round does a lot of tissue damage, but the damage to the vitals is significantly less than if the rifle ballooned at the proper time. Or would the loss of blood from the damaged tissue contribute a lot faster to a physiological stop?

heavydluxe
November 28, 2012, 03:49 PM
Sorry... I think I was not reading your original post clearly. I apologize for the unhelpful link. Here's an attempt at an ignorant, but more helpful reply.

1) With a bullet designed to poke through the target, how much permanent cavitation trauma is there? Or is the bullet just zipping through without upsetting the tissue too much? (as a comparison, I noticed when I was a kid shooting cans with a BB gun that 1 pump would send the cans flying, but 10 pumps would have the BBs just pass through the cans as if the can had never been hit).
The difference is the presence of fluid in the medium itself, I would think. I'm assuming the soda cans you referenced were probably empty. In that case, the only 'resistance' on the projectile is the air and the aluminum. In the case of soft tissue, the fluid in the tissue transmits the shockwave of the impacting round much more efficiently throughout the entire 'vessel'. Right?

Skribs
November 28, 2012, 04:02 PM
While that is true, as the article you linked showed, bullets which are designed with better penetrative capabilities (i.e. smaller meplat to pierce through) transmit less energy into the tissue, creating less of a shockwave. While I agree that energy dump in and of itself isn't the wounding potential, there is a clear indication on the gel tests I've seen that where the energy is dumped is where the wound tract is largest.

RPRNY
November 28, 2012, 04:02 PM
Can of worms. Opener. Proceed.

This issue generates a lot of passion, sound, and fury from advocates of the many obscure and often entirely baseless theories about wounding, particularly amongst those those who, incorrectly, believe that velocity can be transferred into some form of never-actually-named-destructive-energy all out of proportion to bullet weight, diameter and terminal ballistics.

Your childhood BB gun observations do however answer your questions.

A high velocity non-expanding projectile will, without significant yawing inside tissue, cause much less damage than the same weight/shape projectile designed to expand, all other things being equal. Similarly, a lower velocity projectile of the same dimensions that effectively expands will also do more damage than the non-expanding variety. At the target, velocity is only important when A) sufficient to generate bullet penetration and B) combined with bullet design.

A FMJ 5.56 NATO round is designed to yaw to skirt the provisions of international agreements (broadly referred to as the Geneva Conventions) that sought to limit the wounding capacity of military bullets. The wounds from expanding bullets - particularly before the advent of modern anti-biotic treatments, were considered so horrific, that agreements not to use them. Thus, soft tip .22 Hornet ammo issued with WW2 onward aircrew "survival rifles" bore laborious warnings against their use in any combat role, defensive or offensive. The yaw designed into the 5.56 bullet skirts the prohibitions of these agreements but seeks to compensate through bullet performance in the tissue.

Soft point, expanding bullets are used for hunting because they kill. JHP bullets are used by LE for the same reason (no Conventions to worry about). Lead bullets, like the 405gr 45-70 govt round, would maim and kill at very low terminal velocities (prior to the Conventions).

However, everyone has a story about the expanding bullet that over-expanded/fragmented delivering very little penetration and leaving a nasty but non-lethal surface wound. Too much velocity for bullet design.

So, if you want a self defense rifle (always better than a pistol at anything more than arm's length provided it is practical in the confined space you are operating in), the answer is to match cartridge ballistics to bullet design. So, a .270 Win with hollow point bullets would be dubious (unless you were concerned about environmental over-penetration). A .416 Rigby with solids would also not be ideal. A .223 with appropriately designed bullets (and there are plenty) that will expand but not fragment at under 50 yd terminal velocities would be good (not my cup of tea, but good). A 30-30 lever gun with soft-nose cowboy loads would work well too for example. So too a pistol caliber carbine. The key criteria are: suitability of the rifle: a carbine probably better than a 42" battle rifle; suitability of the cartridge (reasonable 100 yard accuracy, relatively soft shooting, no massive fireballs, speed reasonable for the parameters); and design of the bullet (will reliably expand - not rapidly fragment at the terminal speeds envisaged).

Hope this helps.

RPRNY
November 28, 2012, 04:15 PM
Can of worms. Opener. Proceed.

This issue generates a lot of passion, sound, and fury from advocates of the many obscure and often entirely baseless theories about wounding, particularly amongst those those who, incorrectly, believe that velocity can be transferred into some form of never-actually-named-destructive-energy all out of proportion to bullet weight, diameter and terminal ballistics.

Your childhood BB gun observations do however answer your questions.

A high velocity non-expanding projectile will, without significant yawing inside tissue, cause much less damage than the same weight/shape projectile designed to expand, all other things being equal. Similarly, a lower velocity projectile of the same dimensions that effectively expands will also do more damage than the non-expanding variety. At the target, velocity is only important when A) sufficient to generate bullet penetration and B) combined with bullet design.

A FMJ 5.56 NATO round is designed to yaw to skirt the provisions of international agreements (broadly [edit: if incorrectly - see link below to the Hague agreements] ;-) referred to as the Geneva Conventions) that sought to limit the wounding capacity of military bullets. The wounds from expanding bullets - particularly before the advent of modern anti-biotic treatments, were considered so horrific, that agreements were reached not to use them. Thus, soft tip .22 Hornet ammo issued with WW2 onward aircrew "survival rifles" bore laborious warnings against their use in any combat role, defensive or offensive and stressed they were only to be used for survival hunting. The yaw designed into the 5.56 bullet skirts the prohibitions of these agreements by compensating through bullet performance (yawing) in the tissue.

Soft point, expanding bullets are used for hunting because they kill. JHP bullets are used by LE for the same reason (no Conventions to worry about). Lead bullets, like the 405gr 45-70 govt round, would maim and kill at very low terminal velocities (prior to the Conventions).

However, everyone has a story about the expanding bullet that over-expanded/fragmented delivering very little penetration and leaving a nasty but non-lethal surface wound. Too much velocity for bullet design.

So, if you want a self defense rifle (always better than a pistol at anything more than arm's length provided it is practical in the confined space you are operating in), the answer is to match cartridge ballistics to bullet design. So, a .270 Win with hollow point bullets would be dubious (unless you were concerned about environmental over-penetration). A .416 Rigby with solids would also not be ideal. A .223 with appropriately designed bullets (and there are plenty) that will expand but not fragment at under 50 yd terminal velocities would be good (not my cup of tea, but good). A 30-30 lever gun with soft-nose cowboy loads would work well too for example. So too a pistol caliber carbine. The key criteria are: suitability of the rifle: a carbine probably better than a 42" battle rifle; suitability of the cartridge (reasonable 100 yard accuracy, relatively soft shooting, no massive fireballs, speed reasonable for the parameters); and design of the bullet (will reliably expand - not rapidly fragment at the terminal speeds envisaged).

Hope this helps.

Sam Cade
November 28, 2012, 06:10 PM
A FMJ 5.56 NATO round is designed to yaw to skirt the provisions of international agreements (broadly referred to as the Geneva Conventions) that sought to limit the wounding capacity of military bullets.

Geneva conventions deal with the treatment of non-combatants.

Article 23 of the Hague IV deals with small arms during warfare


In addition to the prohibitions provided by special Conventions, it is especially forbidden - <snip>
To employ arms, projectiles, or material calculated to cause unnecessary suffering;

Sam Cade
November 28, 2012, 06:14 PM
I've long been an advocate of rifles for self defense, and plan on getting one in the future, because of how the rifle round does its wounding - with the cavitation trauma.

Fackler found that cavitation is a secondary wounding factor. Sometimes wholly insignificant.

http://bajaarizona.org/fklr/fklr.html

Skribs
November 28, 2012, 06:22 PM
Geneva conventions deal with the treatment of non-combatants.

Yeah but he is correct that most people refer to all of those conventions as the Geneva convention.

I'll have to read that link later.

Sam Cade
November 28, 2012, 06:36 PM
Yeah but he is correct that most people refer to all of those conventions as the Geneva convention.


Those people are painfully incorrect.

http://en.wikipedia.org/wiki/Hague_Conventions_of_1899_and_1907


http://en.wikipedia.org/wiki/Geneva_Conventions

Skribs
November 29, 2012, 11:54 AM
Fackler found that cavitation is a secondary wounding factor. Sometimes wholly insignificant.

I don't know, the size of the wound tract he describes, especially in fragmenting ammo, seems to be pretty significant. My question here basically boils down to this: how reliably can we assume that the biggest target in stopping an attacker - the vitals - will be the recipient of the cavitation trauma as opposed to simply crush trauma?

r1derbike
November 29, 2012, 12:30 PM
Pass-throughs hitting vital organs and main arteries, etc.

Yawing, fragmenting rounds hitting vital organs and main arteries, after sufficient penetration.

Shot placement.

These and more have filled countless hours of study by me. There are so many variables involved, I was reeling with the possibilities.

All I know is that pass-throughs not hitting vital areas may not stop your attacker.

Yawing fragmenting rounds ill-placed, without enough penetration may not stop your attacker.

All the research has left me with more questions, than answers.

Skribs
November 29, 2012, 12:33 PM
All the research has left me with more questions, than answers.

Dangit! I was hoping your point ended with an answer...

RPRNY
November 29, 2012, 01:05 PM
The largest practical diameter projectile that will reliably penetrate and expand at terminal velocities, shot placement being equal, is the most likely to do the most damage. Bigger holes do more damage. There is no substitute for cubic inches. Etc.

But, practical. Overpenetration may be an issue. Distance and trajectory should not be an important issue in an SD based choice, so high velocity really shouldn't be a key part of the equation. Recoil, noise, rifle handling etc., are.

There's a lot to be said for a pistol caliber carbine in .357/9mm/.44Mag/.45 and some case to be made for the .223 with properly expanding bullets...

Carne Frio
November 29, 2012, 01:15 PM
I don't have answers for you. When I want to find out
about terminal ballistics, I go to where the professionals
are. DocGKR, at M4carbine.net, is a Stanford professor
and the moderator at this forum. Probably more info
than you can use, but very interesting.
http://www.m4carbine.net/forumdisplay.php?f=91

68wj
November 29, 2012, 01:44 PM
I don't have answers for you. When I want to find out
about terminal ballistics, I go to where the professionals
are. DocGKR, at M4carbine.net, is a Stanford professor
and the moderator at this forum. Probably more info
than you can use, but very interesting.
http://www.m4carbine.net/forumdisplay.php?f=91
He is good at simplifying a complex subject. Here is his summary commentary relevant to this thread. http://www.m4carbine.net/showthread.php?t=34714

And his 2008 argument for improvement in small arms ammunition. http://www.dtic.mil/ndia/2008Intl/Roberts.pdf

Skribs
November 29, 2012, 02:00 PM
So basically, if I get a round designed to upset early (like the Barrier Blind loads I've been seeing mentioned a lot) then on most hits it will offer the wider wound tract, but on one of those obtuse hits it will still have a yawing rifle round leaving a thin, but long crush cavity?

Compared with a PCC like a 9mm AR, for example, which will consistently yield a roughly circular hole of fairly consistent diameter all the way through.

Robert101
November 29, 2012, 02:18 PM
I do appreciate ones desire to understand the science behind bullet development and wound channel effects. I have very little contribution to that initial request. My post is simply to state my faith in the current offerings from bullet manufacturers and my philosophy of application. What works is already known by hunters and offered by Hornady, Nosler, Sierra, etc. Most often the heavier grain HP/Soft Point bullet then the heavier the application to game. (i.e. in 308 a 180 grain bullet is used on heavier game in lieu of say a 125 grain). Yes, for self defense, I believe a HP or Soft Point bullet is preferred. With that being said, I believe a rifle should also be required to shoot through reasonable barriers and retain enough mass into a target. One thing for sure is that combat is a dynamic and ever changing it has a lot of variables. Finding what bullet creates the ultimate wound channel is not that high on my priority list although I do understand and appreciate your question as more knowledge is a good thing. In hunting, game animals ares hardly ever shot through cover. In combat shooting through cover is a likely occurrence. Im simply stating that my philosophy includes the sacrifice of that perfect wound channel for a bullet that can penetrate some barriers if the need is appropriate.

heavydluxe
November 29, 2012, 02:32 PM
The largest practical diameter projectile that will reliably penetrate and expand at terminal velocities, shot placement being equal, is the most likely to do the most damage. Bigger holes do more damage. There is no substitute for cubic inches. Etc.

But, practical. Overpenetration may be an issue. Distance and trajectory should not be an important issue in an SD based choice, so high velocity really shouldn't be a key part of the equation. Recoil, noise, rifle handling etc., are.
If I read this right, you just added a new discipline to the shooting world - situational ballistics.

You should declare yourself the chair of an appropriate department of research at the ammunition manufacturer of your choice. :)

Shadow 7D
November 29, 2012, 02:47 PM
Please remember that back then it was fine to shoot 'Savages' with a 'Dum Dum or similar ammunition...'

It was just the 'civilized men' who were to be shot with what was considered a 'clean' wound.


Modern ammo has come a LONG ways from the days of 68 caliber round ball.

Skribs
November 29, 2012, 03:09 PM
Heavy, I don't think he meant that if something is bigger than needed it will produce a smaller wound tract. I think he was talking about how you don't want to use something likely to penetrate through 50 inches of tissue just because it will make a bigger hole (thus putting innocents at risk), and you don't want to use something ungainly that, while it makes a bigger hole, also comes at the cost of a heavier platform and greater recoil.

Most people don't advocate a .50 BMG for HD, for example.

heavydluxe
November 29, 2012, 03:13 PM
Sorry... I was just being cheeky. I caught (and even understood) the author's intent. Apologies for the not-so-funny attempt at humor. :)

RPRNY
November 29, 2012, 03:46 PM
If I read this right, you just added a new discipline to the shooting world - situational ballistics.

You should declare yourself the chair of an appropriate department of research at the ammunition manufacturer of your choice.

I like it! I'll be offering an on-line course soon, accreditation pending.

I shall be referred to as Professor henceforth, you heathen....;)

Cosmoline
November 29, 2012, 04:08 PM
I think there is some magic velocity where there is enough energy imparted to the target rapidly enough to make the temporary cavity into a permanent wound.

You're onto something there. I've seen historical references to a "magic" velocity of around 2,100 fps from a rifle round at impact. The "explosive" wounds from rounds of this velocity were first noticed with the advent of smokeless powder in the Spanish-American war from the 7x57 rifles. So it's not just imagination. But it's a fuzzy number, since we're dealing not just with the bullet's physics but the resistance of internal tissues around the particular bullet hole. If the hole goes through fatty tissues, even a very large cavity means little. If it's right next to the heart then it can kill.

Skribs
November 29, 2012, 04:24 PM
I've seen references to a velocity of around 2,100 fps from a rifle round at impact. These "explosive" wounds were first noticed with the advent of smokeless powder in the Spanish-American war from the 7x57 rifles. It's basically the velocity that's just beyond the reach of ordinary black powder firearms.

But it's a fuzzy number, since we're dealing not just with the bullet's physics but the resistance of internal tissues.

I've heard differing numbers as well. One poster on THR (can't remember who atm) had a theory that the caliber of the meplat (expanded or not) would have an effect on the velocity needed to achieve an increase in permanent wound channel. Something along the lines of if you need 2" of cavitation trauma to cause permanent damage, then the cavity needs to stretch 2" - meplat in order to break that threshold. Not sure if that's true or not (it might need to be 2" from the edge of the crush trauma, for example) but it's an interesting take.

That's what I'm referring to by the "balloon" effect, is that the rifle creates a moderate crush cavity (actually probably a smaller crush cavity than a 9mm JHP), but it does its damage through cavitation trauma. In my OP, I was wondering if the bullet just zips through (as multiple sources linked say can happen with a long neck length) then the 9mm will crush more tissue in its path, and actually affect the target more, especially because the long neck length of the wound tract is due to the bullet travelling straight instead of yawing.

So while I can trust the 9mm round to make a 0.6" circular hole through the target, the .223 round may make a 0.223" hole at the neck, a 3" hole during the yaw/fragmentation, or a 0.223x1" hole at the tail-end of the penetration. So at one point the .223 will make a significantly larger hole (thus leading to the target bleeding out faster, which doesn't necessarily mean it will stop the target in the time needed for SD), but at the other points it will make a smaller hole than the pistol cartridge.

Hunting is a little different than SD, because while a hunter wants to kill quickly, it doesn't seem to be that important that the the deer drop RIGHT THERE. A self defense shooter needs the target to stop ASAP.

HorseSoldier
November 29, 2012, 04:38 PM
Wound channels in gelatin have a limited relationship to actual terminal bullet performance, as has been stated. Unless the temporary cavity is through some critical and non-elastic tissue like the liver it may or may not have much bearing on lethality or incapacitating capability.

The big payoff for a center fire rifle round at defensive shooting ranges in the dramatically greater energy it possesses compared to most pistol rounds. The old energy transfer ballistics theories are overly simplistic to the point of being irrelevant, but a rifle round has enough energy that we're not really worrying about FBI clothing/tissue penetration standards. That energy can translate into additional injury from temporary cavity and things like destroying bone and creating secondary fragments -- but it may not, too.

The other big plus with a long gun versus a pistol is just that at self-defense ranges, what are hard/low percentage shots with a handgun are pretty much chip shots with a shotgun, carbine, or rifle.

Skribs
November 29, 2012, 04:46 PM
The other big plus with a long gun versus a pistol is just that at self-defense ranges, what are hard/low percentage shots with a handgun are pretty much chip shots with a shotgun, carbine, or rifle.

I'm not picking between a rifle and pistol, but an intermediate cartridge vs. a pistol cartridge, both fired from a long gun.

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