View Full Version : Response to why 4 layers of denim
Every time 4 layer of denim testing comes up on a message board some guy inevitably replies with "who wears 4 layers of denim?" Here is my response.
I always compare bullet testing to crash testing of automobiles. In both cases we require a repeatable method of testing the interaction of a fast moving object with an artificial representation of a real world object. In both cases we also have people’s lives on the line. I don't see anyone arguing that crashing an automobile with a crash test dummy as a passenger into an energy absorbing barrier at exactly 35mph is stupid, and has no relevance to safety of that automobile. Yet I hear the argument over and over again that denim is not a realistic barrier, and that gelatin is not the same as a person. I have yet to find a person that would pile their kids into a vehicle that crash tests indicated was unsafe because the test is "unrealistic". Yet people choose to ignore scientific testing, and chose ammunition based on anecdotal evidence.
The fact is that these test events, and test parameters are chosen because they are reproducible, and consistent meaning that engineers can track improvements, and provide quantitative analysis that are relevant to all tests regardless of who performs them, or where they are performed (assuming proper calibration of all equipment, and test media).
Just looking at the evolution of defensive ammunition shows how much improvement there has been since the advent of ballistic gelatin testing, and the addition of FBI, and IWBA (4 layer denim) barrier testing. We now have bullets that can expand after passing through a wide variety of materials, and still penetrate over 12" of tissue to reach vital organs. We also now have cars that are safer than ever before. All this is the direct result of tests performed under "unrealistic" conditions using "ridiculous" test media.
I do want to add that real world performance of ammunition is an important part of the equation. This is not lost on ammunition manufacturers, or the FBI (despite what some people may have you believe). The FBI and law enforcement agencies continue to gather data on real world shootings, and some ammunition is still tested using anesthetized animals, as part of the testing protocol.
The undeniable conclusion is that bullets that perform well in calibrated gelatin, and are able to expand after passing through 4 layers of denim tend to perform better in real shootings. Likewise cars that perform well in government crash test are in fact safer than those that do not.
packinaglock
03-17-12, 07:11
Up North folks tend to wear many layers of cloths to keep warm.
Personally I would like to see a test where the layers are increased. I've had a friend who's duty ammo (Federal Hydroshok, 155gr) had failed him twice and in the department they had several shootings in which their duty rounds mushroomed in text book fashion but failed to penetrate heavy winter clothing, winter jackets, leather jackets, half a dozen sweaters, and this is in Atlanta Georgia. Department has since gone to a different round (180gr HST), but they have had at least one case of a failure in that round to penetrate heavy clothing as well. Granted in all cases blunt force was enough to knock the perp down and incapacitate him until the officer could secure the weapon and cuff him. Still if the rounds had penetrated the clothing it would have saved tax payers some money.
I think there are a lot of people who only see the rounds perform in bare gelatin and choose their loads by which has the biggest ending size paying little attention to barrier penetration and how far it actually penetrated in the gelatin. The "it's good enough" mentality, I suppose. Sort of like some people I have talked with who will not train with their pistols beyond 7 meters because 90% of shooting occur within that distance, its good enough be damned if they end up not being in that statistical curve, but I am drifting now.
I started to take a good look years ago in my LE life when changing out new books..
and watching the amount of layers of clothes some shit heads were wearing
often the average was
thermal shirt
tshirt
sweatshirt
thin jacket
then heavy layer of goose down etc/leather
thermals
sweats pants jeans etc...
Some even sport life vests and an oven mitt.
http://2.bp.blogspot.com/_JvSHxoCopfk/TTyECReaZ2I/AAAAAAAAAJE/e-RtbKCn3Fo/s640/huh.jpg
Personally I would like to see a test where the layers are increased. I've had a friend who's duty ammo (Federal Hydroshok, 155gr) had failed him twice and in the department they had several shootings in which their duty rounds mushroomed in text book fashion but failed to penetrate heavy winter clothing, winter jackets, leather jackets, half a dozen sweaters, and this is in Atlanta Georgia. Department has since gone to a different round (180gr HST), but they have had at least one case of a failure in that round to penetrate heavy clothing as well. Granted in all cases blunt force was enough to knock the perp down and incapacitate him until the officer could secure the weapon and cuff him. Still if the rounds had penetrated the clothing it would have saved tax payers some money.
The problem with this is that we are dealing with service calber pistols. By their very nature these are weapons that are portable, have reasonably high capacity, but are not very powerful. They are by their nature a compromise.
We ask a lot of the bullets we fire from these pistols. We want them to penetrate deep enough to reach vital organs, yet we want them to expand to increase the degree of soft tissue damage. These two concepts are diametricaly opposed to each other.
If we look at penetration capability of the 9mm with NATO ball we get about 27" of tissue penetration. This is the best the cartridge is capable of with an unexpanded round nosed projectile. On the other end of the spectrum we have various prefragmented projectiles with penetration in the 4-6" range. Most JHPs will perform somewhere in between. because the bullet has a finite ammount of energy if you increase expansion, and you decrease penetration period. If you want maximum penetration you must have no expansion. The only way to improve performance for your scenario is to limit expansion across the board.
I can devise a test that will cause every single service caliber JHP to fail to penetrate. The problem is that the test proves nothing other than I have tested beyond the capability of the test subject.
If we go back to the crash test analogy we can crash cars at 100mph resulting in nearly 100% failure of every automobile on the market. Does it happen in real life? Sure it does, but a car that can save passengers at 100mph will cost too much, and may not perform it's other functions properly.
If we want penetration, and expansion through the widest variety of possible scenarios we need to step up to 6.8 SPC or even better .308with bonded projectiles. Unfortunately until they make one that fits in a duty holster we are limited by physics.
In cases of failure to stop due to penetration issues (he could also be waering body armor) hardware upgrades are not always the solution. Training, and tactics are just as if not more important, and a shift of aiming point may be required to end the subjects hostile actions.
Alaskapopo
03-17-12, 16:46
Personally I would like to see a test where the layers are increased. I've had a friend who's duty ammo (Federal Hydroshok, 155gr) had failed him twice and in the department they had several shootings in which their duty rounds mushroomed in text book fashion but failed to penetrate heavy winter clothing, winter jackets, leather jackets, half a dozen sweaters, and this is in Atlanta Georgia. Department has since gone to a different round (180gr HST), but they have had at least one case of a failure in that round to penetrate heavy clothing as well. Granted in all cases blunt force was enough to knock the perp down and incapacitate him until the officer could secure the weapon and cuff him. Still if the rounds had penetrated the clothing it would have saved tax payers some money.
I think there are a lot of people who only see the rounds perform in bare gelatin and choose their loads by which has the biggest ending size paying little attention to barrier penetration and how far it actually penetrated in the gelatin. The "it's good enough" mentality, I suppose. Sort of like some people I have talked with who will not train with their pistols beyond 7 meters because 90% of shooting occur within that distance, its good enough be damned if they end up not being in that statistical curve, but I am drifting now.
I have never seen that up here and we get cold (Alaska). People were a lot of layers here. What we do see with Hydra shocks is a totally failure to expand. Penetration is fine because the bullet did not expand. I have to ask did you get your information first hand or was it passed to from him second hand. Heavy clothing does not stop penetration it does slow or stop expansion which generally increases penetration.
Pat
The only way I can see clothing causing premature expansion is if it were soaking wet. Half a dozen soaking wet sweaters could be an inch or more of wet fabric which could result in expansion. I still don't see how it would completely stop the bullet from penetrating though unless the subject was wearing body armor of some type underneath.
Alaskapopo
03-17-12, 19:10
The only way I can see clothing causing premature expansion is if it were soaking wet. Half a dozen soaking wet sweaters could be an inch or more of wet fabric which could result in expansion. I still don't see how it would completely stop the bullet from penetrating though unless the subject was wearing body armor of some type underneath.
I suspect its a story that was passed on once to many and the facts got mixed up.
Pat
A very good article on why 4 layers of denim.
http://www.firearmstactical.com/tacticalbriefs/2006/04/02/0604-02a.htm
... Therefore the four-layer heavy denim test is NOT intended to simulate any type of clothing; it is merely an engineering evaluation tool to assess the ability of JHP handgun bullets to resist plugging and expand robustly.
The only way I can see clothing causing premature expansion is if it were soaking wet. Half a dozen soaking wet sweaters could be an inch or more of wet fabric which could result in expansion. I still don't see how it would completely stop the bullet from penetrating though unless the subject was wearing body armor of some type underneath.
It could of been wet, but the suspect was coming out of a liquor store, when the officer stopped him, suspect turned and raised a gun when he did so, officer fired two rounds center mast. Suspect had on top layer heavy leather jacket, then several sweaters(Never got an exact number so it could have been rather high since if memory serves said perp was a vagrant), finally a T shirt. My theory has always been it acted like a bullet catch padding the round while letting it expand and reducing its ability to penetrate. Left nice bruises but did not penetrate at all, when the jacket was pulled open the slugs popped off. So they may have stuck in the jacket, but other then some bruising the perp was okay. If he had been wearing armor underneath I would have expected the bullets to have stopped there, and I think there would have been a greater uproar over a perp wearing body armor during an armed robbery in metro Atlanta.
As far as it being a story that got lost in translation, I live next door to the cop who dropped the hammer, or striker as it may be since department issue is a Glock, I don't see why he would be lying since its not like he hasn't been in the shit before.
While I am thinking of it. Failure could have been caused due to old ammo being repeatedly chambered(Seen round failures due to this personally, not opening as designed and actually tumbling(230gr PMC Starfire if anyone cares), but then I would have only have expected a single failure not two, though if you cycled the top two rounds when unloading reloading then perhaps not out of realm of possibility.
Alaskapopo
03-17-12, 23:30
It could of been wet, but the suspect was coming out of a liquor store, when the officer stopped him, suspect turned and raised a gun when he did so, officer fired two rounds center mast. Suspect had on top layer heavy leather jacket, then several sweaters(Never got an exact number so it could have been rather high since if memory serves said perp was a vagrant), finally a T shirt. My theory has always been it acted like a bullet catch padding the round while letting it expand and reducing its ability to penetrate. Left nice bruises but did not penetrate at all, when the jacket was pulled open the slugs popped off. So they may have stuck in the jacket, but other then some bruising the perp was okay. If he had been wearing armor underneath I would have expected the bullets to have stopped there, and I think there would have been a greater uproar over a perp wearing body armor during an armed robbery in metro Atlanta.
As far as it being a story that got lost in translation, I live next door to the cop who dropped the hammer, or striker as it may be since department issue is a Glock, I don't see why he would be lying since its not like he hasn't been in the shit before.
While I am thinking of it. Failure could have been caused due to old ammo being repeatedly chambered(Seen round failures due to this personally, not opening as designed and actually tumbling(230gr PMC Starfire if anyone cares), but then I would have only have expected a single failure not two, though if you cycled the top two rounds when unloading reloading then perhaps not out of realm of possibility.
I don't think anyone is lying but I have seen a lot of things get lost in translation especially from fellow cops who just did not understand what they were being told. Also if the clothing had stopped the bullet it would not have been a perfect mushroom because there would not have been fluid involved. It would have looked like a bullet shot into a vest or other hard object. The nose would have caved in on itself looking more like a smashed rivot than a mushroom.
Pat
vicious_cb
03-18-12, 00:03
Kind of sounds like that old myth that .30 carbine would not penetrate the heavy winter clothing during the korean war. I doubt there is any amount of clothing a person could reasonably wear that would even slow down a common service caliber.
Kind of sounds like that old myth that .30 carbine would not penetrate the heavy winter clothing during the korean war. I doubt there is any amount of clothing a person could reasonably wear that would even slow down a common service caliber.
I second this statement. Why buy a bullet proof vest when a leather jacket with lots of cotton padding would save officers lives? When a 180 gr HST bullet will penetrate plywood, drywall and steel, I have to believe heavy leather would not stop a it. If the round hit a metal flask inside the jacket or a large pocket knife or other metal object, maybe it wouldn't penetrate but I am still betting on the HST. Maybe the homeless guy was Hancock (Wil Smith).
The other thing that makes me call BS is the fact that clothing usually causes rounds to OVERPENETRATE due to the clothing clogging the hollow point, which causes the round NOT to expand. Heavy clothing rareley ever causes less penetration.
JHPs tend to penetrate MORE after going through heavy clothing, not less, and this is due to lack of expansion of the bullet.
I will go out on a limb and call this story complete and utter bullshit. I will go so far as to say that either someone is lying or the BS of the story got tuned up a notch over several tellings of the story.
I have seen stories like this take on a life of their own way too many times.
The ".30 carbine doesn't penetrate heavy/frozen clothing" is one such story, the BS ref the Penn. gunfight FBI Powerpoint that flew around the intardnets is another where the .40 "only penetrated 1" in flesh and stopped fully expand" or in one version after not expanding at all.
Even pissant rounds get through some very heavy clothing rather nicely.
An example would be a shooting we had here, home invasion suspect shot several times, one of the over 50 year old .38 special standard velocity RNL bullets from a model 36 had to get through the folds and front zipper of a set of Carhart coveralls, two sets of blue jeans underneath, long Johns, boxers, enough tissue to ricochet off of the pelvis and then travel upwards a foot and a half through the intestines. Next bullet went through a quilted parka, the Carharts, a hoody, sweatshirt, T-shirt, hit the left clavicle and deflected downwards and penetrated all the way into the liver.
Not really scientific, but the point is made here;
Heavy clothing;
http://www.theboxotruth.com/docs/bot8.htm
Heavy frozen clothing;
http://www.theboxotruth.com/docs/bot36_2.htm
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