New thoughts about bullet fragmentation and temporary cavitation

[Webleymkv]

In researching some of the work of Dr. Martin Fackler, I came across this article:

http://ammo.ar15.com/project/Fackler_Articles/effects_of_small_arms.pdf

In the article, I noticed the greatly increased permanent cavity caused by 5.56x45 and 7.62x51 bullets that fragment. I also noted the following passage pertaining to the 7.62x51:

"Note the greatly increased permanent cavity. Tissue pieces are detached by the synergistic effect of bullet fragmentation and temporary cavitation.

and also this:

"Projectile fragmentation can greatly augment temporary cavity effects by providing points of weakness on which the stretch is focused rather than being absorbed evenly by the tissue mass."

Now, this information was mainly relating to the performance of centerfire rifles. Fragmentation in a handgun bullet usually isn't preferable for a self-defense application because it typically limits penetration severely.

However, I started thinking about loadings such as the older Remington and Federal .357 Magnum 125gr Semi-Jacketed Hollowpoints. These loadings produce, for handguns, quite large temporary cavities because of their high kinetic energy (nearly 600 ft. lbs.) and their aggressive expansion. These loadings also routinely fragmented (usually shedding pieces of their jacket) but still retained acceptable penetration (usually in the neighborhood of 12"). The fragmentation of these loadings also seemed to typically occur much deeper into the target than a typical fragmenting handgun bullet such as the light 90gr 9mm loadings or the early .357 Sig loadings.

As many are already aware, these .357 Magnum loadings had a particularly fearsome reputation for effectiveness in the 1970's and 1980's when they were popular with police. Many police departments such as the Indianapolis Metro Police Department and Texas State Highway Patrol reported near-rifle type effects with this loading out of proportion to its paper ballistic figures. Many of these departments also reported very little difference in terminal effect even with the velocity reduction common to firing these loadings from a short barrel.

This leads me to believe that the more controlled fragmentation of these loadings at deeper penetration than is possible with fragmenting bullets of most of the other common handgun cartridges (.38 Special, 9mm, .357 Sig, .40 S&W, and .45 ACP) may produce a synergistic effect similar to those observed by Fackler with centerfire rifles. This would explain the reputation of these loadings for delivering terminal effect out of proportion to their paper ballistics. I wonder if such an effect may have been overlooked in the past 25 years of study since the vast majority of bullet development in that time has been for semi-automatics which are likely not to feed a semi-jacketed bullet reliably. This leads me to wonder if perhaps the best performing self-defense bullets might be ones which produce "controlled fragmentation" for lack of a better term. Does anyone have any other thoughts, comments, or insight on the matter?

 

[C0untZer0]

I can't find the paper right now but Dr Gary Roberts and Dr. Martin Fackler delineate between temporary wound cavity created by handgun bullets and rifle bullets. Temporary wound cavities caused by high-velocity rifle bullets are associated with significant tissue damage, typical handgun bullets traveling at typical handgun velocities are not. The .357 fired from a long barreled pistol can reach velocities higher than most other handgun bullets.

What I'm saying basically - my understanding is that when it comes to temporary cavitation being associated with significant tissue trauma, it's not bullet design, it's velocity.

 

[kraigwy]

I don't read many papers but I have some experience with hand gun bullets.

The Anchorage Police Department issued 125 JHP Winchester 357 Ammo. I figured it was probably a good round for LE.

EXCEPT

As a cop in Anchorage there was a more chance of shooting critters then people. In the winter, moose use roadways as they were easier traveling then the deep snow. We had several moose - vehicle encounters. Most of these critters needed to be put down and the cars towed.

I was never a cop that was fond of shotguns, I figured if I couldn't handle it with my service revolver, I had a counter-sniper rifle in the truck.

I did a lot of moose dispatches with my Model 28, only I wasn't happy with the 125 JHP Mag stuff. I did much better with LSWCs. I carried reloads, using the 150 grn LSWC Lyman 358477. It was much more effective then the 125 grn stuff.

I use the same bullet today in my 642 in 38spl. It works on putting down deer (no moose here), and dispatching hogs for butchering. I also used the same bullet, but in 357 out of my APD Issued Model 28 (which they gave me when I retired) to kill a buffalo I bought to butcher. It also worked on a rather large dog who was contesting my right to get my mail out of my mail box.

To each his own, but I'll stick to my LSWCs.

This guy was charging my patrol car after winning a dispute with a van and sending several other cars into the bar pit.

 

[mete]

There are many variables and bullet development continues. Note that premium handgun bullets are bonded with no separation [which is in effect fragmentation] .Lead alloy of the core varies from pure lead to 1.5% Sb to 3% Sb IIRC .Then there are the all copper types , DPX, TSX . I want no fragmentation ,no jacket separation , full penetration [especially for hunting]. The round must be able to penetrate into the vitals to do a good job.

 

[C0untZer0]

Photographer cut your head off...

 

[Webleymkv]

originally posted by C0untZer0

What I'm saying basically - my understanding is that when it comes to temporary cavitation being associated with significant tissue trauma, it's not bullet design, it's velocity.

Perhaps I didn't convey my thoughts as clearly as I would have liked in my original post. I'm not so much wondering about the temporary cavitation causing permanent tissue damage in and of itself, but more about the temporary cavitation working synergistically with fragmentation at relatively deep penetration depths to increase the permanent crush cavity out of proportion to the expanded diameter of the bullet. The best illustration I can find is within the link when you compare the permanent crush cavities of the yawing FMJ 7.62x51 loading to the expanding and fragmenting .308 Winchester loading. Really, a picture of a ballistic gel test with the loadings I'm talking about would convey the idea better, but the ones I've seen were quite old and I can't seem to relocate them. Really, gelatin tests with .357 Magnum loadings are fairly rare and most of them that can be found are with newer non-fragmenting loadings like Speer Gold Dots and Hornady Critical Defense.

originally posted by kraigwy

The Anchorage Police Department issued 125 JHP Winchester 357 Ammo. I figured it was probably a good round for LE.

EXCEPT

As a cop in Anchorage there was a more chance of shooting critters then people. In the winter, moose use roadways as they were easier traveling then the deep snow. We had several moose - vehicle encounters. Most of these critters needed to be put down and the cars towed.

I agree that in your case, the 125gr SJHP would have been a poor choice. However, animals are quite different than people and your experince with using a handgun to put down large animals is probably fairly unique to your location and profession.

originally posted by mete

There are many variables and bullet development continues. Note that premium handgun bullets are bonded with no separation [which is in effect fragmentation] .Lead alloy of the core varies from pure lead to 1.5% Sb to 3% Sb IIRC .Then there are the all copper types , DPX, TSX . I want no fragmentation ,no jacket separation , full penetration [especially for hunting]. The round must be able to penetrate into the vitals to do a good job.

In most handgun calibers, I agree with you. However, the particular loadings that I'm talking about perform quite differently than most other common self-defense bullets do. While they routinely shed their jackets, the bullet's core typically remains intact and usually still has enough penetration to reach the 12" minimum.

You see, these loadings have relatively thin jackets which make up a small percentage of their weight when compared to other JHP bullets (the core of a fully expanded round usually weighs 80-100gr IIRC). I suspect that the only reason these loadings even have the jacket to begin with is to prevent leading from driving a soft bullet at such high (1400fps+) velocity.

Also, the lead core is quite soft and is thus more likely to either remain intact, or fragment into relatively few large pieces which still penetrate well rather than exploding into many small, shallow penetrating fragments within the first few inches as some other JHP designs are apt to do.

Basically, I wonder if these loadings create the same type of gruesome looking wounds that other fragmenting bullets like like Glaser Safety Slugs do, but at deeper depth where they are better able to cause such ghastly damage to vital organs rather than a nasty-looking superficial wound. To my understanding, the reason that fragmentation is undesirable in handguns is because it limits penetration depth to shallower-than-adequate levels. These loadings, however, seem to deliver both fragmentation and adequate penetration.

As I said before, the thought I'm trying to convey here would be more easily illustrated with pictures. I've seen pictures of gelatin tests with these loadings before, but I can't seem to relocate them. If anyone could be so kind as to post such pictures or point me in their direction, I would greatly appreciate it.

 

[irish52084]

Your thought process is sound. The idea is that if a bullet can both penetrate to an acceptable depth and also provide violent fragmentation of the jacket, you have a possibility of more effective incapacitation.

There are some hunting bullets that work in a similar manner. In my own hunting experience I've noticed that plastic tipped bullets that were not bonded exhibited violent expansion after penetration roughly 3" of whitetail deer. In most cases, the jacket would separate from the lead core and often the expanding petals of the jacket would fragment and cause some pretty nasty damage. The cores were usually found on the underside of the hide after almost complete penetration of the animal or had completely passed through the animal. Usually there was one large exit wound from the core and several smaller wounds from jacket pieces.

Keep in mind most of this personal data was gathered from shots fired from less than 100 yards and all were very effective in dropping game. Most did not run and died in the spot they were shot.

Does any of this mean anything when it comes to pistol rounds? I think the general principle does apply. If you can get 12"+ of penetration by the core and rapid expansion and fragmentation of the jacket in vital areas, you can increase the potential for a fight stopping injury.

In the end there are no magic bullets and where you hit matters more than what you hit with. 22lr to the eye socket and it's all over, 7.62x51 to the big toe sucks, but you're probably gonna live.