FMJ Overpenetration: Truth or Myth?

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SonOfScubaDiver

New member
So, I'd like to get opinions on the topic of over penetration with FMJ. There seems to be some controversy over the likelihood of over penetrating a target with FMJ and other non-hollow point rounds, thereby hitting innocent bystanders in the process. I don't claim to be a ballistics expert, but I have learned a couple of things since becoming a gun enthusiast. Well, at least I think I have.

In the first place, it seems to me that there is a lot of confusion surrounding the 12-18 inch penetration standard. I constantly hear people claiming that this standard does not account for bones, tendons, or other aspects of the human body. My understanding is that the 12-18 inch penetration standard actually represents 4-6 inches in human flesh once bones, tendons, and other aspects of the human body are factored in. In other words, a bullet that can penetrate 12-18 inches of ballistic gel should have enough force to penetrate a human body and reach vital organs, which is approximately 4-6 inches. If I'm wrong on this, feel free to correct me.

The thing that has me thinking about this over penetration claim is that, if it's true that 12-18 inches of penetration in gel approximates 4-6 inches in actual human flesh, then a bullet would have to travel with enough force to almost triple that amount before actually passing through the upper torso. And then it would have to still be traveling fast enough to penetrate whomever is behind the person getting shot. In other words, a bullet would have to pass through the ribcage, reach the heart (or other vital organ), pass through the heart, and then still have enough force to pass through the ribcage again before becoming a danger to someone standing behind the person being shot.

So, while I know that bullets do strange things when entering the human body, and while I know that it wouldn't take as much force to completely pass through the abdomen, intenstines, and out the tissue in the lower back region of the body, it seems to me that there isn't nearly as much danger of over penetrating someone with FMJ as people are claiming.

I mean, that's a big part of the sales pitch with hollow points, right? They expand, mimicking a larger round (not a bad thing), and lose all their energy before going completely through the human body. The risk of over penetration is greatly reduced, but how much of a risk is there in the first place? With some calibers, such as the 380, it seems to me that the risk of under penetrating a target is higher with hollow points than the risk of over penetrating a target with FMJ.

So, I'd like to get your opinion on over penetration with FMJ. Is the risk real, or is it just a myth concocted by bullet manufacturers to get us to buy more expensive hollow point ammunition?
 
Depends on the round.

.45 ACP tends to overpenetrate 50 percent of the time (but I presume thinner people more, overweight people less but who knows.)

9x19 fmj, being semi-pointed, even more, .380 being weaker, less.

Deaf
 
It would depend like Smith said.
I almost went with FMJ in .380 but after seeing testing where they was getting over 26 inches in gel, and even simulated "meat" targets.

I decided to go with JHP's

The potental for over penetration and hitting a innocent is there.. no denying that.
what the exact odds are I don't know I guess it depends on the situation.

Ideally there would be no one behind your target to hit neither via miss or over-penetration but let's face it, If you have to shoot you're gonna shoot.

Until someone comes up with a better benchmark Im gonna pick my SD loads based on gel tests that conform to standard.
 
I think the overpenetration issue is a moot point.
In a stressfull situation, how many hits out of 10
hit the target. Years ago I heard or read 8 out of 10
rounds fired by authorities were misses!
 
45 acp HP bullets (HST) that expand in my own tests and this video penetrate to rear 3rd jug of water:
https://www.youtube.com/watch?v=f2mWTafCFwY
I've seen a video where 45 HP that failed to expand blew out the back of 7th jug of water, can't find it, here 45 blows out rear of 6th jug - last one.
https://www.youtube.com/watch?v=Xl3dSwl-Kq4

In water, 45 FMJ has double (or more) the penetration of a HP that expands.

Heavy clothed gel test:http://www.luckygunner.com/labs/self-defense-ammo-ballistic-tests/
45 HST 230 penetrated 14'' / .85
45 Starfire 230 did not expand 29'' / .45

In gel, 45 HP that did not expand has double (or more) the penetration of a HP that expanded.

There are examples showing 45 FMJ penetrates twice as far a a HP that expands.

Notably absent is what I think subsequently unsupported by data. ;)
 
Here's an excellent article by Massad Ayoob where he discussed the subject of overpenetration and documents cases of it actually occurring. https://gundigest.com/gear-ammo/reloading/massad-ayoob-the-dangers-of-over-penetrating-bullets

I do not carry FMJ for personal defense. The only reasons that I can imagine anyone would desire to do so are:

-- To save money
-- Because hollow points won't cycle reliably in their gun of choice
-- For protection in outdoor environments where over penetration is not a concern
-- Your state doesn't allow them
 
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SonOfScubaDiver wrote:
In the first place, it seems to me that there is a lot of confusion surrounding the 12-18 inch penetration standard.
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Yes, there is.

The standard exists to provide a uniform basis for comparison, not to provide any direct analogue to the human body.

I constantly hear people claiming that this standard does not account for bones, tendons, or other aspects of the human body.
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This is correct.

It does not account for the different tissue types. Nor was it ever intended to.

My understanding is that the 12-18 inch penetration standard actually represents 4-6 inches in human flesh once bones, tendons, and other aspects of the human body are factored in.
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What's your source for this?

Whether FMJ or hollow-point, if a pistol bullet strikes bone half an inch into the target, it is unlikely to go much further.

To the extent that someone assumes 12 inches of gel is "equal" 4 inches of human body, it is the result of a statistical analysis of the probability of encountering certain types of tissue given a particular point of aim. It certainly cannot be taken as anything other than a generalization and not a hard and fast rule.

So, I'd like to get your opinion on over penetration with FMJ.
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"Over-penetration" is a phenomenon observed with all bullet types fired at close ranges, it is not limited to FMJ.

Is the risk real, or is it just a myth concocted by bullet manufacturers to get us to buy more expensive hollow point ammunition?
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Yes, the risk is real no matter what you are shooting.

Setting aside the "conspiracy theory" tone of the question, soft and hollow point projectiles are designed to expand upon entering a target and thereby having a larger diameter are more likely to expend all of their energy within the target. The objective of such projectiles is enhanced lethality of the target, not protecting by-standers behind the target.

The fact soft and hollow point bullets may be more likely to remain in the target and not pass through to strike something behind it is a benefit when used in close quarters. It was not a motivation for creating the projectile types although it is a benefit you may wish to pay to have.
 
SonOfScubaDiver wrote:
So, does anyone know what one jug of water translates to in terms of the human body?
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It doesn't.

The mechanical properties of flesh and water when struck by a projectile at high speed are so very different that there is no ready comparison.
 
hdwhit, I don't have the source information, unfortunately. I don't remember where it was that I read it. I'm fairly certain that it was in an article that explained the purpose of the study and who all was involved with it.

Since you asked for my source, do you have a source that disproves the 12-18 inches in gel approximating 4-6 inches in flesh? If that isn't correct, I'd like to know for sure. There's so much information online that it's hard to know what is true and what isn't. Thanks.

And yeah, I get the reasoning behind hollow points expanding and that they were created to do the damage a larger diameter round would do. That's one thing I like about them. But my main carry gun is a 380. All the expansion in the world won't amount to a hill of beans if the round can't reach vital organs. If I have to shoot anyone, it won't be to injure them.
 
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SonOfScubaDiver said:
Since you asked for my source, do you have a source that disproves the 12-18 inches in gel approximating 4-6 inches in flesh? If that isn't correct, I'd like to know for sure. There's so much information online that it's hard to know what is true and what isn't. Thanks.

And yeah, I get the reasoning behind hollow points expanding and that they were created to do the damage a larger diameter round would do. That's one thing I like about them. But my main carry gun is a 380. All the expansion in the world won't amount to a hill of beans if the round can't reach vital organs. If I have to shoot anyone, it won't be to injure them.
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Lucky Gunner which I linked above includes 380 - a couple of 380 loads penetrate 12'' and expand, but you are questioning gel testing.

I've tested these loads myself, 4 layer denim in front of gallon jugs of water.
Each of these loads stopped at the rear of 3rd jug, typically cracks open rear of 3rd jug, dents 4th, expanded bullet recovered in 3rd jug.
9mm Federal HST 124 gr. +P @ 1,210 fps / 403# KE - expands .6x
45 acp Federal HST 230 gr. @ 863 fps / 380# KE - expands .8x
10mm Handload 180 gr. Gold Dot @ 1,146 fps / 525# KE - expands .7x

Water is a consistent media for testing, IMO based on those loads, penetration past the back of 3rd jug is deep.

These two bullets made it into the 4th jug (deep penetration):
357 Sig Speer Gold Dot 125 @ 1,363 fps / 516# KE - expanded to .5x
40 S&W Speer Gold Dot 180 @ 1,008 fps / 406# KE (same bullet as 10mm just slower with less expansion) .6x

If a bullet penetrates deeper than a 357 Sig Gold Dot or 40 S&W 180 gr. Gold Dot - one might wonder whether it is excessive. ;)

380 HP that did not expand went through 5 jugs (after 4 layer denim) in this test:
https://www.youtube.com/watch?v=njyIRszTFw0

I shot a Gold Dot 380 of of LCP and it blew out the rear of 4th jug - looks like I needed another jug, in this test it tried to make it out the back of 5th jug
https://www.youtube.com/watch?v=NNAURhvFmew
 
"...over penetration with FMJ..." Isn't just them. An HP will go a long way too. In any case, the whole issue is how far a bullet will go after missing. Not how far after a through and through.
The only part of a human carcass that will affect a bullet, mostly small ones, is bones. Bullets go through tendons like they're not there.
"...can't reach vital organs..." Humans aren't like game animals. The slightest bit of shock, like that from a disintegrating bullet destroying tissue, drops 'em.
Water has nothing to do with anything.
 
The many works of Dr. Martin Fackler represent the basis of modern terminal ballistics. I sugest reading the work he did for the military and general terminal ballistics as he is (or rather was) the premier scientist in developing tests that compare wound channels from different angles in three dimensional targets.

You can't rely on expansion from a pistol bullet. It has been shown that pistol HP bullets do not reliably expand in the correct area of the body to do the damage necessary for debilitation. There is scientific work that has been done in this area and it is available to anyone with internet access or access to a decent library. Dr. Fackler is the person who has done the most work in this area.
 
Whether FMJ or hollow-point, if a pistol bullet strikes bone half an inch into the target, it is unlikely to go much further.
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Unlikely? perhaps, but not impossible, it all depends on the bullet, and the bone. I saw a fellow shot with a .357 Mag 160gr SWC and it SHATTERED 17cm of bone (and by shattered I mean no piece bigger than about 1/4" inch long. And it exited.


Humans aren't like game animals. The slightest bit of shock, like that from a disintegrating bullet destroying tissue, drops 'em.
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I don't believe this to be true.

Humans ARE like animals in one regard, each and every one of us is different.

Over penetration is both a myth and a fact, confusing as that sounds. Lots of bullets will go through a human, at their thickest part. Some of us think that is a desirable thing. Others don't. Police agencies, especially large ones, who may have hundred of officers on duty at any give time, can have dozens of shootings in a year, each and every one different. You and I are unlikely to ever have to shoot someone, so our calculation of acceptable risk ought to be different.

Remember, its only "over" penetration when you don't want it. When you do, its "enough" penetration.

personally I don't hold much with ANY "agency standard" or tests. Because none of them can duplicate the real world accurately. Even the real world doesn't duplicate itself, exactly.

Remember that the 9mm JHP that "failed" during the FBI Miami shootout, met every standard. Still failed to stop the shooter. FBI's answer? change their standards...

There is no magic bullet, there is no bullet that can be counted on to just go far enough, and no more. Every attempt to create a bullet that does that encounters the problem that under certain conditions it will not go far enough.

Personally, I'm more comfortable with the idea that it will go through than "it might be enough".
 
Here's an excellent article by Massad Ayoob where he discussed the subject of overpenetration and documents cases of it actually occurring.
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Mas always is an excellent read. One would be wise to read his article!

Deaf
 
...there is a lot of confusion surrounding the 12-18 inch penetration standard...
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There is, but not because of a lack of clear information on the topic. Rather, the confusion arises because people either disregard the available information due to strong opinions, or don't look for the data because they assume they already know what they need to know.

The point of ballistic gel was to provide a more convenient target medium than using actual dead or live animal tissue for testing. Obviously it can't perfectly replicate living animal tissue, but it's good enough that it's still in use decades after Fackler demonstrated its usefulness.

Ballistics gelatin was developed to provide results that were similar to pig muscle tissue, both in terms of projectile penetration and projectile expansion. Pig tissue is a close analog to human tissue.

https://en.wikipedia.org/wiki/Ballistic_gelatin
http://www.frfrogspad.com/gelatin.htm
https://en.wikipedia.org/wiki/Martin_Fackler
http://www.dtic.mil/dtic/tr/fulltext/u2/a570804.pdf
http://www.luckygunner.com/labs/self-defense-ammo-ballistic-tests/

My understanding is that the 12-18 inch penetration standard actually represents 4-6 inches in human flesh once bones, tendons, and other aspects of the human body are factored in.
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That's not accurate.

For any given shot, due to the variables, real-world penetration will not precisely match what is achieved in gel, but the idea that it is going to be consistently less by a factor of 2 or 3 isn't at all realistic.

It does a good job of replicating real-world penetration when small bones (ribs, spine, etc.) are hit.

When major bones are hit the gelatin figure is likely to be high by a factor of two compared to actual penetration. When no bones at all are hit, the actual penetration may be higher than gelatin figure by 50%.

http://www.rathcoombe.net/sci-tech/ballistics/methods.html

"The data the author used for ordnance gelatin tests correlated well with lengthwise shots encountering some ribs and portions of the spine, a good example of typical shot conditions. If major bones are struck (shoulder) the penetration is right at half the depth observed in gelatin tests...if no bones are hit the actual penetration may be almost 50 % greater than the gelatin depth...[/quote]​

Bottom line is that it is supposed to represent human tissue and it does its job as well as can be expected given the obvious variables that can't be eliminated.

In other words, we need to keep in mind that major bones will reduce penetration compared to gelatin figures and that the gelatin figure will be low compared to actual when no bones at all are hit, but with those caveats, we can have a reasonable level of confidence that the gelatin penetration figure is going to provide a useful analog for determining average real-world penetration. It does what it was developed to do which is the reason that it's still in common use.

So when ballistics gel data tells us that FMJ 124gr 9mm or FMJ 230gr .45ACP both penetrate about 2 feet, that's useful information that can be translated to average real world penetration as follows:

If small bones are hit, we would expect about 2 feet of penetration--the gel figure.

If major bones are hit, we would expect only about 1 foot of penetration--about 50% of the gel figure.

If no bones are hit, we would expect as much as 3 feet of penetration--about 50% more than the gel figure.
 
One source, maybe M. Ayoob himself, observed that, contrary to computation and artificial media tests, .45 ACP hardball is less likely to exit a human torso than .38 Special lead roundnose, the "widowmaker."

One anecdote, two bullets, a friend had occasion to shoot an assailant.
Double tap in the chest with USGI .45 hardball from a USGI 1911A1, neither bullet exited.

And, as said, the misses are more common and more dangerous than shoot-throughs.
 
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