Response to why 4 layers of denim

[bernieb90]

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]

Up North folks tend to wear many layers of cloths to keep warm.

[Kain]

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.

[Steve]

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...

[Javelin]

Some even sport life vests and an oven mitt.

[bernieb90]

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]

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

[bernieb90]

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]

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

[wrinkles]

A very good article on why 4 layers of denim.

http://www.firearmstactical.com/tact...2/0604-02a.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.