More on Bullet Penetration — and Why We Don’t Use Bones When Testing Ammo in Gel

In an earlier article I discussed the reasoning behind the recommendation that a bullet needs to be able to penetrate at least 12″ of ballistic gel.  But I’m still seeing confusion and commentary about how people think that’s totally unnecessary, and the reasoning usually goes like this:

“I just measured my torso.  I’m 8″, front to back.  And that means my heart (and other vitals) are only about 6″ deep.  Therefore, a bullet would only need to penetrate 6″, and needing 12″ is just useless overkill.”  Simultaneously, these are usually the same folks who say “Why don’t you (or why doesn’t anyone) ever use bones in your ammo tests?”

The answer to both is the same — ballistic gel, while a tissue simulant, is not a BODY simulant!  Ballistic gel doesn’t attempt to mimic a human body.  It never has been used for that (by professional testers) and it never will be.  Bodies are made of all sorts of tissue — soft stuff, squishy stuff, hard stuff, nearly-empty stuff, really wet stuff, all sorts of things.  No ammo test can accurately simulate all that.  And it’s unnecessary to even try.

Here’s the thing, and I hope that this comes across as non-confrontationally as I mean it to be: the standards that we’re discussing (such as ballistic gel, and 12″) were made by people far, far more expert than the average person.  These standards were arrived at by consensus of ballistics experts, trauma surgeons, doctors, E.R. personnel, coroners, all sorts of people who deal with bullets on a daily basis.  So when considering these recommendations, please understand that a LOT of serious thought went into making them, by the best minds in the business.

Okay, so — back to the bones & 12″ part.  What you need to understand is — the 12″ requirement already includes the presence of bones!  If a bullet can penetrate 12″ of ballistic gel, then it also can penetrate a ribcage and still have enough energy to reach those 6″ into your 8″ torso and hit the vitals.  That’s the whole point, really — specifying 12″ of gel penetration (not body penetration, but gel penetration) means that the bullet has enough reach to hit the vitals from any angle, and through any barrier on the body.  It will have enough power to blast through a bone and reach the vitals underneath.

So when you see people testing bullets by putting pork bones in front of ballistic gel, they’re really going about it the wrong way.  The bone factor is already accounted for in the 12″ recommendation!

Yes a bullet might be able to hit your vitals if it penetrates only five inches of body.  But five inches of body, and five inches of ballistic gel, are not the same thing — not at all.

Think about it from a backwards perspective — gather a bunch of trauma surgeons and ER doctors and combat medics and coroners/medical examiners together, and ask them what bullets have most frequently shown the ability to hit the vital structures.  Then take those same bullets and fire them into ballistic gel, and report the results.  That’s a simplified view of how the 12″ number was arrived at — effective, manstopping bullets that reached deep into the vitals, were then compared using ballistic gel, to see how much penetration is necessary.  And the results were that 12″ of ballistic gel performance equates to “able to reach the vitals from any angle, through bones, and even through a raised arm or sideways through a shoulder or lowered arm.”

In the FBI report “Handgun Wounding Factors & Effectiveness”, the recommendation is made that while penetration up to 18″ is preferable, a bullet MUST be able to reliably penetrate 12″ of soft body tissue at a minimum, whether it expands or not.  For emphasis, let me repeat: “reliably penetrate 12” of soft body tissue“.  Bodies are not made solely of soft tissue, obviously, and the heart isn’t always 12″ deep.  But ballistic gel is a soft tissue simulant.  It doesn’t simulate bones, and it doesn’t need to.  The bone factor has already been considered, and the determination is: if a bullet can travel through 12″ of soft tissue, then it also has enough power to hit the vital organs even when passing through the ribcage.

Now, a bullet may deflect when it strikes a bone, that’s true.  But how can we possibly test for that? Because a bullet may not deflect when it strikes a bone, it might just pass right through.  There are so many variables involved, that you could literally drive yourself mad trying to account for all of them.  Accordingly, ballistic experts don’t bother with all that.  The one overriding, underlying, and immutable factor is: if a bullet is going to have the power to reach the vital organs, through all foreseeable barriers (such as a raised arm, or an angled shot), then that same bullet, when fired in ballistic gel, will travel at least 12″ and preferably up to 18″ through ballistic gel.

Do you see the difference?  It’s not saying your vital organs are located 12” deep in the body (although, for some particularly fat or particularly muscular individual, I guess that’s possible).  Ballistic gel is not a body simulant.  It is a soft tissue simulant, and all experts involved with its creation and use are well aware that bodies are made of more than just soft tissue.  They’ve put some serious thought into this, they’ve conducted some serious science on it, they’ve correlated it against many, many “real world” shootings and autopsies, and the consensus recommendation coming from the 1987 and 1993 wound ballistics workshops is: performance of 12″ minimum, and up to 18″ maximum, penetration through ballistic gel is necessary for a bullet to be considered reliably capable of causing instant incapacitation of a target (assuming, of course, that the shot placement is suitable).

So what about overpenetration?  More on that, in the next article.

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24 thoughts on “More on Bullet Penetration — and Why We Don’t Use Bones When Testing Ammo in Gel

  1. Pingback: Final Results of the .380 ACP Ammo Quest | Shooting The Bull

  2. rw walden

    aaahhhh.

    understand about the gel. did see a video using a pork shoulder (bone and meat) where the result was more stunning that an gel test. that is, the bullet literally exploded the bone and meat, leaving not just a notable “stretch wound”, but a significant cavity caused by impact, expansion, bone fragmenting, meat tearing/ripping apart. the graphic depiction was useful to demonstrate impact power, and stark reminder of what the result of receiving a high-speed bullet might be.

    cheers,

    Reply
  3. rw walden

    just a thought here….would be willing from time-to-time to donate a box of ammo, might be more expensive due to shipping to you, but if it is just something you are full-stop waiting on availability….

    email is always open

    cheers

    Reply
    1. Shooting The Bull Post author

      Donations are always welcome, but you’re right the shipping costs can make it impractical. Especially when you consider that you can’t use the USPS to ship it, you have to use UPS or FedEx. But if you have a specific round you want tested, and it’s not on my agenda to get to, let me know and we may be able to work something out. Thanks for the offer and the generosity!

      Reply
  4. rw walden

    not a specific round in mind, only an offer to help obtain ammo if in short supply in your local area. might be able to find here, or online. now and again, it shouldn’t prove prohibitive. all in the spirit of being part of the great experiment. time in life to support some of my interests instead of being just a taker.

    cheers,

    Reply
  5. Pingback: Dem bones, dem bones… | Shooting The Bull

  6. rw walden

    have liberty civil defense (previously halopoint), 9mm 50gr, 2000fps. willing to ship you a box if you would be interested in testing.

    cheers,

    Reply
  7. Justin

    First off ballistic gel is not a soft body tissue equivalent. Its closer to the density of muscle. To think of it in this term its an average density of soft tissue, muscle, and bone. So say you take densities of all those three then average them then thats ballistic gel. But since muscle is kinda in between bone and soft tissue so its more comparable to muscle than soft tissue. If youve gutted a deer and cut through ballistic gel then you know what I mean. But I think the magical 12 inch mark is a little much. I honestly think the magical number should be 10 inches. Cause to me and from previous evidence from LE shootings show they over penetrate alot. I think its partly cause of the high standards set by the minimum of 12 inchs thinking. I think it should be minimum of 10 inches and maximum of 16 inches. If its going to 18 or even more your gonna get over penetration. Also this magical 12 inch mark made by over exaggerating has caused ppl to think the .380 caliber is insufficient. When you see the .380 caliber hitting at around 10 inches typically ppl get the idea that its not enough. When in reality it really is. Just like they over exaggerated the caliber going from 9mm to 10mm then realizing they were wrong then making the .40 I think they should realize 10 inches to 16 inches would be better and cause less over penetrating issues. But they hate to admit they were wrong.

    Reply
    1. Shooting The Bull Post author

      The 12″ mark isn’t an arbitrary line in the sand, it was determined at the 1987 Wound Ballistics Conference (convened by the FBI after the results of the “Miami Shootout”.) It takes into account the very real possibility that you may have to shoot through 4″ of arm.

      The initial report from the 1987 conference specified a minimum of “10-12 inches”. The 1989 report by Urey Patrick clarified that by calling for a specific 12 inches. It is possible that if someone presented a completely unobstructed target (i.e., they stood in front of you with their arms spread wide) then yes, a .380 that penetrates 10″ would definitely be enough. But can you count on that? If the situation is so dire that you’re forced to resort to using deadly force, then it’s also not too likely that you’re going to get a “free shot” at an unobstructed target. If someone’s pointing a gun at you (and most especially if they’re using a Weaver stance) then the odds of you having to shoot through an arm are really rather high. And if the arm absorbs 4″ or more of your bullet’s penetration potential, that doesn’t leave a lot left over to do the work of incapacitating that attacker.

      The 12″ minimum was not established as the minimum necessary to be able to cause incapacitation. It was established as the minimum necessary to be able to cause incapacitation FROM ANY ANGLE and THROUGH INTERVENING ARMS. Because you simply don’t get to pick and choose your shooting scenario. You may be lying on your back on the ground, having to shoot upwards at an attacker standing over you. You may be facing an attacker who’s turned sideways towards you, thus necessitating shooting through the thickest portion of their arm. You don’t know, and can’t predict, what any individual shooting scenario may involve. Accordingly, they set the standard at a level that would allow success regardless of the angle, and regardless of the barriers.

      If we were talking about a “belly gun” (i.e., something you jam straight into someone’s gut and pull the trigger) with no intervening arms possible and no odd angles to worry about, then yes, no doubt 10″ would be adequate. In my forthcoming review of a small .22lr revolver, I modify my recommendations specifically to account for the type of usage that gun is likely to be employed as. But for a general-purpose defensive weapon, which may be deployed in uncertain and unpredictable scenarios? I’m definitely more comfortable with ammo that can reach the full 12″ minimum (and, preferably, more — I’m much more comfortable with it able to reach 14-16″.)

      Another factor to consider — you don’t want the bullet to just “reach” the vitals — you want it to reach and destroy the vitals. And that means it has to be moving fast enough to actually be able to do some damage. A bullet that penetrates to only 12″ might be just slowly poking along when it reaches the vitals, and it might make a small hole. Whereas a 15″ bullet might be still traveling at a pretty good clip when it reaches the same spot, and it might rip a big hole in the vitals.

      As for overpenetration, if you read the 1989 report from agent Patrick, he pretty well addresses that — the fears of overpenetration are vastly overblown when contrasted against the fact that a very, very high percentage of shots fired by officers just plain MISS the target entirely. A shot that misses is tremendously more dangerous than one that’s traveled through a body, already expanded, and already slowed down.

      Reply
  8. Justin Reynolds

    First off ballistic gel is not a soft body tissue equivalent. Its closer to the density of muscle. To think of it in this term its an average density of soft tissue, muscle, and bone. So say you take densities of all those three then average them then thats ballistic gel. But since muscle is kinda in between bone and soft tissue so its more comparable to muscle than soft tissue. If youve gutted a deer and cut through ballistic gel then you know what I mean. But I think the magical 12 inch mark is a little much. I honestly think the magical number should be 10 inches. Cause to me and from previous evidence from LE shootings show they over penetrate alot. I think its partly cause of the high standards set by the minimum of 12 inchs thinking. I think it should be minimum of 10 inches and maximum of 16 inches. If its going to 18 or even more your gonna get over penetration. Also this magical 12 inch mark made by over exaggerating has caused ppl to think the .380 caliber is insufficient. When you see the .380 caliber hitting at around 10 inches typically ppl get the idea that its not enough. When in reality it really is. Just like they over exaggerated the caliber going from 9mm to 10mm then realizing they were wrong then making the .40 I think they should realize 10 inches to 16 inches would be better and cause less over penetrating issues. But they hate to admit they were wrong.

    Reply
  9. Mike Orick

    People have looked at damage pattern correlations between gel and bodies in actual OIS. While the avg is close, the range is different. Back in 1991 Wolberg looked at shootings w the Win 147 JHP used by the San Diego PD. Head and shots that hit bone were excluded, and only shots into the torso that remained in the body for the entire penetration depth were included in the study. In gel the Win 147 avgd 13 inches, w a range from 12-14 inches. In 27 shootings it avgd 13 inches, but the range was from 10-17 inches. Source Wound Ballistic Review, Winter, 1991.

    Reply
    1. Shooting The Bull Post author

      Yes, it’s been correlated and found to be close, but obviously it will never be exact. We can’t simulate a shot to the body because every shot will be subject to a million different variables, and bullets sometimes react differently and perform differently even in a homogenous medium like ballistic gel. And, because gel has been correlated against bodies and found to be comparable, that’s a good reason why adding bones is the wrong thing to do — it throws the correlation off.

      And, that said, there’s also the question of the first few inches. A BB will penetrate 3.5″ of ballistic gel, but a BB won’t bust through a person’s clothing, skin, fat, muscle, ribs, and into their heart. A BB may or may not even break the skin, but if it does, there’s very little chance of it making it past the ribcage. So it would be unwise to directly say that 1″ of gel = 1″ of body penetration. In aggregate, on average, using full-power bullets, yes they do generally perform equivalently over the full course of the bullet’s travel (meaning, the bullets penetrate about the same depth, and expand to about the same size) and because of that, gel is an excellent tissue simulant. But in the absolute particulars and especially on the short end (such as what will happen in the first few inches) I don’t think it’s reasonable to say they’re directly comparable.

      Ballistic gel makes an excellent medium for comparing one bullet to another, for getting consistent results and consistent tests with minimized variables. And it does give us an overall picture that is comparable to what happens in real street shootings, as correlated by Wolberg’s study and by other studies.

      Reply
  10. Allen Vestal

    The Pancreas and Liver are considered vital organs. I am still waiting for someone to explain how creating a lot of damage to the liver is more likely to stop an a attacker than a sucking chest wound from a small caliber bullet that does not do well in the FBI test.

    If people were not willing to question authority figures we would all be Catholic believing the the sun rotated around the earth.

    https://www.google.com/url?q=http://articles.latimes.com/2005/sep/02/science/sci-bullet2&sa=U&ved=0CAkQFjACahUKEwjjt7fe5fnHAhVDi5IKHXV0A4Y&client=internal-uds-cse&usg=AFQjCNGXoujpGkumFub-feRFgHYFRC0EBA

    Reply
    1. Shooting The Bull Post author

      Why would anyone consider the pancreas or liver as vital to stopping an attack? The FBI standards certainly don’t. There’s a huge difference between “vital for life” and “vital for consciousness”. The FBI standards are all about disrupting the circulatory system, with the goal being to drop the blood pressure quickly to induce unconsciousness. That’s it. The organs that are of interest in stopping someone quickly are the brain stem, the spinal column, and the circulatory organs. That’s all they’ve ever talked about. Any mention of pancreas or liver or stomach or lungs or anything else, is a tangent that they never discussed or promoted.

      Reply
      1. Allen Vestal

        In one of your videos you state if you are not willing to risk hurting an innocent person you should stick with a golf club. I am not willing to hurt an innocent person but is really a choice between one or the other? You can try the golf club first., a taser 2nd and a gun 3rd. The FBI has a mandate to take out dangerous criminals that people in a self defense situation do not. Do we need to be able to penetrate barriers? You might find yourself in jail if you try.

        Reply
        1. Allen Vestal

          Average exchange of gunfire in self defense situations takes place at 20 feet with an average of 3 shots fired. The person who gets off 2 shots usually wins. Recoil and muzzle flash determine who is more likely to get the second shot. It is much more complicated than what goes the a certain distance in a gel block.

          Reply
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  13. John

    As stated elsewhere, the concern over there being over penetration is vastly overblown, as statistics show that VERY few innocent bystanders have received gunshot wounds as a result of over penetration. However, there are numerous examples of bullets that underperform and exhibit a lack of penetration, for whatever reason (eg. barriers, etc.). And the last thing one wants to bring to a gunfight is an underperforming round that lacks the penetration ability to actually stop the fight asap. In addition, if one is in a gunfight, there may be times when there is a usefulness in being able to shoot through furniture, etc. in order to incapacitate a bad guy.

    For me, I think a minimum of 18″-20″ of penetration in gel is a whole lot better than merely 12″ or 14″, at least for the variables that can possibly be encountered in some random gunfight. I believe that those who are obsessed with the notion of overpenetration may have simply not been involved in a protracted gunfight and have not experienced and suffered the consequences of their not being able to land effective hits on a life threatening target due to various barriers, including: hands, arms, extra thick clothing, cell phones, baseball bats, etc., etc.

    When will the talk of the myth of overpenetration ever end?

    Reply
  14. Colin Maxon

    I’m sorry but I do not agree with the testing standards and think they need to be reevaluated. I get that 12 inches in ballistics gel is not 12 inches in the human body, but the thing is when you test bullets in just ballistics gel you are most likely always going to get the bullet to perfectly mushroom; and that is just not going to be the case when shooting something that has a bone structure. I think in order to see the specific cartridges full potential there has to be some form of a bone structure as to see if the round can reliably expand after passing through the bone. Just because the FBI says it needs to be a certain way doesn’t mean it is the right way and we can’t question it. Any thoughts?

    Reply

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