surrogate measures for wounding effectiveness

[antsi]

Nolo's thread about up-loading .45 ACP got me thinking about the different measures people use as surrogates for the effectiveness of a handgun round in wounding/incapacitating an assailant.

It seems to me that there are several factors that play in to this. There are also a number of different measures or statistics people use to quantify these factors.

I thought I'd try to catalog them, along with the advantages and disadvantages of each measure.

Permanent wound channel: A function of penetration and the (expanded) diameter of the projectile. Measured under controlled laboratory conditions (ie, shooting tissue simulating gel).
Advantages: Most of the more scientific ballistics gurus tend to emphasize physical damage to vital organs as the most reliable/effective mechanism of wounding from handgun shootings. Permanent wound channel seems like it would reflect the ability of a handgun round to damage vital organs.
Disadvantages: uncertain what extent ballistic gel accurately simulates human tissue - invites the question whether or not these measures reflect real world shootings. Testing is expensive, and not all loadings have been tested or tested thoroughly.

Kinetic Energy: Calculated from the mass and velocity of the projectile.
Advantages: Easy to calculate; produces a single number that is easy to compare between calibers/loadings.
Disadvantages: Not clear to what extent greater energy translates into greater wounding/incapacitation effectiveness: does more energy create effects simply via penetration and expansion? Or does energy have effects beyond the physical destruction of tissue? Formulas may exaggerate the effectiveness of lighter, higher velocity projectiles since velocity increases energy geometrically while mass increases energy arithmetically.

Sectional Density: Calculated from the cross-sectional area and mass of the projectile
Advantages: Easily calculated and compared. Thought to be the main determinant of penetration.
Disadvantages: Doesn't take into account velocity, which also influences penetration. May exaggerate the effectiveness of heavier bullets given the same caliber (ie; 147 grain 9mm vs. 115 grain 9mm).

Street Results: Data gathered from actual shootings and/or autopsy results
Advantages: reflects real world performance
Disadvantages: Newer or more unusual calibers are not well represented (fewer shootings = smaller sample). Data usually is not collected or analyzed in a controlled systematic way, so conclusions are not scientifically reliable.

I know there are some others... what do you use to compare the expected performance of different calibers and why do you rely on that measure?

 

[1911 guy]

One good way.

Theory has a way of falling apart when confronted with real life. I'd need to see results in test media at the very least to put my faith in a new wunder round. Frankly, there are too many good and proven rounds to choose from to be tempted by a newcomer for a serious social gun. 9mm, .40S&W, .357SIG, .45acp, 10mm, .38, .38Spcl, .357mag, .44Spcl, and that's just the ones off the top of my head.

 

[Soybomb]

Disadvantages: uncertain what extent ballistic gel accurately simulates human tissue - invites the question whether or not these measures reflect real world shootings.

I recommend more research here because there are several papers out there that test ballistic's gel's suitability. It is a suitable tissue simulant. One of the more interesting ones is from the winter 91 IWBA journal by Eugene Wolberg. He compares the gelatin test results of the 147gr ranger load with measurements taken from autopsies of people shot by that round by the san diego pd. You can find plenty of fackler documents easily as well on it.

The other flaw with this method is that the gel tests often aren't done under proper conditions. People do these tests in their back yard, don't store the gel properly or make it properly, and then its not in spec. The end readers often aren't into ballistics enough to know about the requirements for proper gel tests and just take the results as true because it was gel. For example I believe there is a popular site with lots of shotgun gel tests but the results are from an out of spec block. A casual reader might wind up selecting a round that performs very differently than they were led to believe it would if they didn't notice.

Street Results: Data gathered from actual shootings and/or autopsy results
Advantages: reflects real world performance
Disadvantages: Newer or more unusual calibers are not well represented (fewer shootings = smaller sample). Data usually is not collected or analyzed in a controlled systematic way, so conclusions are not scientifically reliable.

I think you need to be more specific here. I consider the previously mentioned Wolberg paper to be street results. I think you're alluding to the M&S data, if so lets just say so. The M&S data is flawed in so many different ways that I don't consider it usable. Ymmv.

 

[RecoilRob]

Some may differ with me, but when talking about handgun cartridges...throw out the kinetic energy equations as they don't count here.

Back in the olden days, with velocity limited by blackpowder, if you wanted more killing power you used a bigger-heavier bullet. Period.

Then came the smokeless revolution that removed the old speed limits and people were looking for ways to equate the new high-velocity rounds with the old. Particulary Mr. Weatherby wanted to advertise that their 'little' bullets were the equal or superior to the Big Old Ones. Enter Kinetic Energy calculations that are heavily influenced by the velocities and give a big edge to the smaller-faster bullet.

Does this work in the real world? Yes....for rifles. Over 2000fps starts to create the 'hydrostatic shock' syndrome that IS effective sometimes....but not many pistols can get anywhere near that speed, so KE measurements only muddle the waters.

Momentum combined with sectional density will very accurately determine the penetrative power of the pistol round, and this is the ONLY thing you can really count on to do your work...which is putting a hole in the target.

Bigger hole = better. Deeper hole = better too, unless it gets all the way through...then any more is wasted and just makes shooting more difficult.

If you limit your pistol thinking like this, you will find the comparisons easy to make and be better served than worrying about the 'majic' aspects of bullet performance. (flame suit on!)

 

[antsi]

I recommend more research here because there are several papers out there that test ballistic's gel's suitability. It is a suitable tissue simulant.

I consider the previously mentioned Wolberg paper to be street results. I think you're alluding to the M&S data, if so lets just say so.

I wasn't trying to "settle" the argument about lab vs. street - just acknowledging that this debate exists. It's not unique to the problem of wounding effectiveness - it is often true in scientific inquiries that improvements to internal validity (usually meaning more strict experimental controls) make the study conditions less like real life. Trying to study the phenomenon under real-life conditions improves external validity, but generally means less control over extraneous variables and thus poor internal validity (ie; difficult to draw conclusions based on the data).

 

[Markbo]

I believe any of the lab tests have things against them. Now if you dressed ballistics gel in clothing and made it with bones inside, maaaaaybe it would be a better substitute.

I don't believe anything other than real life information means didly. If some of the superloudenboomers are not represented, so be it. It has been quite easy for me to choose 3 or 4 rounds with proven results documented in the real world and then simply choose which of those shoots best in that pistol.

It seems pretty easy to me.... then again, I like simple.

 

[Soybomb]

Now if you dressed ballistics gel in clothing and made it with bones inside, maaaaaybe it would be a better substitute.

Bones would make it worse. Gelatin is supposed to be a uniform benchmarking substance. If I introduce the variable of hitting bones or not and the deflection from it I'll no longer be getting those repeatable results that I'm looking for. Its the same reason we wouldn't want to float a liver in it. Many gel tests for hollow point handgun rounds are shot against "clothed" gelatin.

I wasn't trying to "settle" the argument about lab vs. street - just acknowledging that this debate exists.

"uncertain what extent ballistic gel accurately simulates human tissue" There should be no uncertainty or debate here, the academic work has been done. I still think it would be better to be more specific. If you're talking about wolberg's work of actually measuring penetration and expansion from corpses, thats street results. If you're talking about M&S telling you what bullets stop people better, thats just as good as an anecdote at the gun store.

 

[antsi]

I don't believe anything other than real life information means didly.

That's the problem though - information collected from real life can't be obtained in as controlled or systematic a fashion as laboratory data. When you try to draw conclusions, you are very likely to be influenced by all kinds of biases you don't recognize or can't account for.

Most times, the most reliable way to make decisions is to correlate data from the real world and from controlled conditions. Without having read it myself, the Wolberg study soybomb mentioned sounds like an opportunity to compare real life results to lab results. If both kinds of data are supporting the same conclusion, it strengthens the finding. If the two different kinds of data point in different directions, you're at a loss.

If you're talking about M&S telling you what bullets stop people better, thats just as good as an anecdote at the gun store.

Right - there is a lot of anecdotal based information out there on the web besides those you mention. Recently there was a thread here linking to someone's web page that was essentially just a lengthy exposition of anecdotes he had collected over his career - however, he also threw in a lot of technical-sounding jargon to create the appearance of a scientific approach. I think some of the M&S data has the same problem - presenting statistics derived from anecdotes. It's actually potentially more misleading than gun store anecdotes because it has the appearance of systematic analysis.

 

[Markbo]

Bones would make it worse. Gelatin is supposed to be a uniform benchmarking substance. If I introduce the variable of hitting bones or not and the deflection from it I'll no longer be getting those repeatable results that I'm looking for. Its the same reason we wouldn't want to float a liver in it. Many gel tests for hollow point handgun rounds are shot against "clothed" gelatin.

Well if humans were only made of a standard tissue and didn't have organs of differing mass, volume and density and we could all walk around without bones I suppose it would be suitable to BE so uniform.

But my whole point was that humans are NOT uniform. The entire basis of my remarks were that humans involved in shooting introduce all sorts of variables that to simply ignore because gelatin is a clean and uniform substance doesn't mean much other than to compare one round against another... it CANNOT duplicate humans being shot so it's usefulness is very limited.

If what you are looking for is repeatable results, then just choose one round and keep shooting gelatin. It should all look the same. Me... I don't care about that a bit. I am much more concerned about how do loads A, B, C, etc, etc, etc behave in the real world because my concern is about bad guys... not gelatin guys.

 

[CAnnoneer]

Good points about clothing and bones above. Remember that the human body contains over 200 bones of varying size. A gelatin dummy usually contains none. Also, muscle is much thicker, harder, and denser than fat. That's why I don't put much stock in gelatin results - at best they are a very crude boundary value as to what real life is like.

I'd say shooting cadavers may be quite educational, but rigor mortis and dehydration will certainly affect the results.

Bottom line is: shoot what you are fastest and most accurate with, and keep shooting until the threat disappears. Some targets can take a lot of punishment before stop being a threat, others far less. Pouring over marginal advantages from one caliber to another just feeds the "one-hit stop" myth.

Incidentally, if gunowners as a community present a united political front on the stupidity of "one-hit manstopper superbullets", we might stand a far better chance winning the political battle over AWB magazine capacity. "High-cap mags make sense in self-defense".

 

[Soybomb]

Well if humans were only made of a standard tissue and didn't have organs of differing mass, volume and density and we could all walk around without bones I suppose it would be suitable to BE so uniform.

Perhaps think of it this way, we may have different tissue densities but if you can come up with the right average, you could make a pretty good benchmark. Maybe you go through liver and lung easier than muscle. Don't try to match the density of any of the three, find the right average. If you tried to simulate the varying densities in the block you'd find it impossible to create a useful tool. Its not perfect and you're going to see a range instead of exact matching results between gel and people but its surprisingly close.

it CANNOT duplicate humans being shot so it's usefulness is very limited.

As I suggested to the fellow earlier, you owe it to yourself to do more research because there are several journal articles out there showing that it does exactly that. For instance in the article I cited earlier the round penetrated 13 inches with an expansion ratio of 1.20. From the wound tracts measured in corpses created by this bullet the average penetration depth was found to be 13 inches with an expansion ratio of 1.15. These are not new ideas or tests, the article I cited was from 1991 and the bulk that you'll find of people testing just how accurate of a tissue simulant ballistics gelatin is will be even older than that. These are good academic quality journal articles too, you just have to want to read about this stuff. We'd just shoot into water if we just wanted a uniform test, ballistics gel is a proven simulant.