[coylh]

What's the correlation between penetration depth in 10% gelatin versus people? It sounds like people assume they are equivalent. I would think they would be dramatically different, because gelatin is uniform but people are lumpy, stretchy, bony, etc.

[kudu]

That's always been a big debate and many gun writers have addressed the issue. Gelatin is an easy way to test some of the effects of how a projectile will act when hiting soft tissue. Unfortunatly is shows none of the effect of what clothing or bone and muscle tissue will do to the performance of bullets. Its main effect is to show dramatic effects to people so they think "wow that's awsome, I'll have to get some of those bullets."

Either way gelatin willgive you some rference of what type of penetration you can expect out of certain bullet. My 2 cents, FWIW.

[Dave McCracken]

Any correlation is not much better than an educated guess seasoned with wishful thinking.

Gelatin has no adrenaline fueling it,no bones,no organs of varying sensitivity, no empty air pockets.

One can get a rough approximation of apples to apples by comparing a load to one of known effect that performs similarily in gelatin, but the key word is roughly.

[Sarge]

for government work.

[Mike Irwin]

The bones issue isn't as much of a crusher as you'd think.

Gelatin has never been touted as being the "perfect" testing media, or as even giving exact results. That's been an invention of the gun press and those who don't like gelatin because it pokes holes in their own pet theories.

What gelatin does, provide, however, is something that closely approximates the average mean density of human tissue (note the use of the term AVERAGE mean density).

That means that it strikes a balance between the combined densities of bone, muscle, organs, etc.

The biggest proponent of gelatin testing has been Dr. Martin Fackler. Quite frankly, he's got the credentials as a former military trauma surgeon (Vietnam) to say whether gelatin is a valid testing media or not. His credentials are one hell of a lot more impecable in that field that, say... Gus Gunguyonsky, mouth-breathing editor of "Lower West Thumbsuck Tractor, Combine, and Handgun Review Monthly."

Figure it out, folks. There's a reason why gelatin has been accepted by the major ammunition companies, FBI, etc., as a testing medium.

Is it because it's easy to prepare and work with? You've got to be kidding.

Is it because it's cheap? Righttttttttttttttttttttttttttt...

Is it because a test can be whipped up in 5 mintues? snicker...

It's because it is, by far, the closest thing we have to a medium that replicates performance of a bullet in human flesh -- INCLUDING bones, organs, muscles, and fat. Remember that "average mean density" concept?

The only other alternative right now is to start shooting people, and that's not going to happen any time soon.

Still don't believe it?

Next time a gun writer starts talking about how dubious ballistic gelatin is as a testing media, ask him how many gunshot wound victims he's operated on in his career, and ask him how that correlates to his personal experience in shooting prepared gelatin.

Chances are, you'll just get some hemming and hawing, and a blank look. (As a former "gun writer -- Associate Editor of American Rifleman magazine), I've shot gelatin, but I've never operated on someone.

The people who have done both, however, including Dr. Fackler, are convinced of gelatin's efficacy, and quite frankly, in the absense of anything MORE effective (you see the gun writers trashing gelatin, but do you see them coming up with a better mousetrap? Nope, they ain't paid for that, I guess...), I'll take the data from gelatin testing as the most pertinent we have.

[coylh]

Yeah, I'm not opposed to testing in gelatin. What I was wondering was if 12" of penetration in gelatin equals 12" of penetration in people, on average.

[Mike Irwin]

No correlation can ever be direct, but Dr. Fackler indicates that it should be close.

[TrapperReady]

I prefer pudding, but lime-flavored gelatin is OK once in a while.

[Denny Hansen]

What Mike said. Also, results can be scientifically reproduced when testing any given load. Anecdotal data (the mythical one-shot stop) can't be.
Denny

[CWL]

Properly calibrated gelatin offers a consistent test medium. This is great for repeating tests, comparing various loads, calibers, velocities, thru clothes, barriers, etc. Anyone, anywhere in the world should be able to reproduce the same results. as opposed to clay, phone books, rump roasts...

Dr. Fackler is a pathologist, this means that he not only treated the live ones, but looked into the dead ones as well.
He was also responsible for standardizing gelatin mixture @ 10% rather than 20%.

[dport]

Mike, well stated!

A couple of police departments out west, San Diego was one IIRC, compared their gelatin test data to actual shootings. The results, while not exact, were close. Of course, you won't find that in a gun-rag. They are professionals who share their data with other professionals to be peer-reviewed, as credible researchers do. Unlike Joe Blow the gun-writer. There also have been correlations to the resistance a layer of skin provides against a bullet upon exiting to 10% gelatin(Skin provides more resistance to a bullet upon exiting than upon entering. Think of it this way. Take a package of meat and poke your finger against the clear plastic wrap. It breaks relatively easily. Now take the same clear plastic wrap and try to poke your finger through it with nothing behind it. The clear plastic wrap will stretch and deform before your finger will break through. The same goes for skin.). IIRC it's equivalant to 4" of gelatin.

[Shawn Dodson]

Differences in density between various soft tissues is irrelevant with regard to bullet expansion, as discussed below.

The claim that gelatin is homogenous and people aren't, and that this difference is somehow an important factor in terminal performance is without merit.

There are two forces acting on a bullet when it penetrates soft tissues: 1) inertial forces and 2) shear forces.

According to MacPherson*:

"Shear force may be thought of as the force that resists deformation; if you push on a wall you are creating shear forces in the wall that resist your push. If you push your hand down very slowly on a water surface, you feel no resisting force; this is true because a liquid cannot support a shear force (in fact, this nonsupport of shear forces is really a definition of a liquid). This lack of shear force support is the reason a liquid assumes the shape of the container it is placed in.

"You can fan your hand back and forth in air quite rapidly because there seems to be no resistance, but a similar fanning motion cannot be done nearly as rapidly underwater because moving the water can take all the strength you can muster. The forces that resist the movement of your hand in water are inertial forces, and are due to accelerating the mass of water (giving it a velocity). There are also inertial forces that resist the movement of your hand in air, but these forces are so much smaller that they are not obvious because air density is so low. (Moving your hand also produces inertial forces because your hand has mass, but we are used to the feel of this because it happens all the time.)

"A bullet penetrating a soft solid (tissue or a tissue simulant) meets resistance that is a combination of shear forces and inertial forces...

"...the force resisting a bullet penetrating soft tissue at velocities above the cavitation threshold (about 500 ft/sec for typical handgun bullets) is almost totally an inertial force; in effect, this force is due to accelerating a mass of tissue in and near the bullet path. This force is nearly identical to the force resisting a bullet penetrating water (which as a liquid does not support a shear force) at velocities above the cavitation threshold because the densities of water and tissue are nearly the same. This is the reason bullet expansion is usually nearly the same in water, tissue, and gelatin (the small differences are due to effects that are not important here, but are described in Bullet Penetration)...

"The extension of these dynamics to soft tissue variation is obvious. Different types of tissue present different resistance to finger probing by a surgeon, but the surgeon is not probing at 1000 ft/sec. Different tissue types do have differences in the amount of shear force they will support, but all of these forces are so small relative to inertial forces that there is no practical difference. The tissue types are closer to each other than they are to water, and bullet expansion results prove that the dynamics of penetration in water and tissue are nearly identical at velocities over 600 ft/sec where all bullet expansion takes place (see Bullet Penetration for a detailed explanation of bullet expansion dynamics)."

*MacPherson, Duncan:"Wound Ballistic Misconceptions." Wound Ballistics Review, 2(3), 42-43; 1996.

Why aren't bones cast in gelatin blocks? Because expanding bullets are designed to expand in SOFT TISSUES, not bone. Additionally the type of tissues we're trying to damage -- vital tissues -- are all soft tissues.

The effect that striking bone has on a penetrating bullet's terminal performance is, in many cases, unpredictable, and depends on where the bone is located along the bullet's penetration path, the type of bone encountered, thickness/density, angle of impact, etc. Because we cannot predict what bone our bullet may hit, testing bullets against bone produces information of little practical value.

(However the most likely bone to be encountered is rib bone, and tests conducted using rib bone have shown negligible effect on a bullet's terminal performance.)

[dport]

Shawn,
Do you have some sort of internet radar that guides you to these sort of threads?:D

[Mike Irwin]

Shawn has very finely honed Geldar...