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Bullet Penetration Depth..?

Discussion in 'Caliber Corner' started by thegriz18, Nov 1, 2010.


  1. thegriz18

    thegriz18
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    I've noticed that everyone makes a big deal about pistol bullet penetration depth listing 12 inches as the bare minimum a bullet must penetrate to be considered reliable for use. However, the .223 is used by many of these same agencies and the rounds that are used in .223 ammo typically barely make 12 inches in gel. Am I missing something, or does that not make any sense at all?
     

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  2. glock20c10mm

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    No, you're not missing anything. The 12" number is nothing more than a good rule of thumb. Even Dr. Fackler said that the ~8" penetration depth that some of the 9mm 115gr HP loads muster up is usually enough.

    Me personally, as long as a given load is good for around 10" penetration depth in clothed gel, I'm happy. And when I'm not in bear country, that's why I like Double Tap's 10mm 135gr Nosler bullet load. For most situations I'm not interested in more than 11" penetration depth.

    Sometimes in my spare mag I'll carry a heavier bullet weight just in case it's needed (of course that will only help if I have time to switch mags :shocked: ).

    12" penetration depth is not a requirement. Some guys want their carry load to penetrate more than that, and others like me, less.


    Good Shooting,
    Craig
     

  3. DocKWL

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    What you are missing is the character of the work done by a rifle bullet as compared to a hangun bullet. Two totally different animals.
     
  4. English

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    The 12" minimum penetration requirement comes from the FBI and is combined with a 16" or 18" (I don't remember which) maximum. Following the Miami shootout in which bad guys continued to kill good guys after receiving shots which would have killed them sooner if they had penetrated just a little further, the FBI decided that they needed a better round than the .38 Sp and set out to find one. Penetration depth was part of the testing criteria. The FBI were also very concerned with fights with BGs in or behind cars and so they wanted enough penetration to do a lot of damage after a bullet had passed through a car body or windscreen.

    If you look at the various photographs of bullet damage to ballistic gellatine which are infiltrated with die, you will see that the last third to a quarter of the penetration is actually smaller than caliber. In contrast the earlier part, even from the 147gn 9mm, which is the worst, is very significantly greater than caliber. In this region the damage done by the bullet is done to a large volume of gel or tissue and so the heart, for example does not need to be hit directly by the bullet to be incapacitated. In the later section of its travel, the only damage is to tissue on the direct path of the bullet and so this region is almost wasted relative to a rapid incapacitation except for very fortunate shots. This does not mean entirely wasted of course, as the autopsies from that event showed, but bullets tend to deflect once they hit a body and so even the most well placed shots can miss their internal target.

    The reality of gunfights is that BGs do not stand upright and square on while you shoot at them and so a bullet might hit an arm before it gets to the body or the shot might pass at some odd angle through a depth of body before it gets to something vital. So there is considerable justification for the FBI's depth of penetration criterion which we can think of as a major damage for the first 8 inches and minor damage thereafter. Often enough, minor damage is better than none.

    What you then have to consider is the applicability of the FBI model to a civilian gunfight. Do you expect to be fighting BGs behind cover or is the more likely scenario a fight at close range with no cover. If it is the latter then penetration becomes less significant and a wide zone of damage becomes more significant. there is no perfect answer to all scenarios.

    English
     
  5. 481

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    Doc,

    As I've come to expect, you are spot on. :supergrin:


    For those with open minds interested in learning more about the characteristics of either phenomena (handgun and rifle projectile penetration and terminal behavior) there are excellent sources available that can provide scientifically sound material explaining the nature of the two.

    A valid perspective and understanding of handgun bullet penetration mechanics can be obtained by reading, "Bullet Penetration", by Duncan MacPherson. While heavily reliant upon math/calculus to illustrate the operation of his well researched model, a cursory reading "around the math" involved can provide an improved understanding of terminal ballistics to the lay reader.

    Written and published more than a decade prior (1990) to MacPherson's work is that of Professor Carroll E. Peters (Professor of Mechanical and Aerospace Engineering, University of Tennessee), which also succeeds in describing valid mathematical models for the penetration of both rifle and pistol bullets.

    Finally, there is the work of Mssr. Jean Victor Poncelet (1788-1867), a French mathematician and engineer who served under Napoleon during the War of 1812, who developed a differential equation (employing hybrid methodology) for expressing mathematically the penetration of (non-deforming) bullets of his day. While it does not address today's expanding designs (like JSPs, JHPs and EFMJs), it does provide an illuminating insight into the basics of the discipline of Penetration Mechanics.

    I'd encourage anyone truly interested in learning more about bullet penetration and terminal performance to have a look at these three predictive models.


    :)
     
    #5 481, Nov 1, 2010
    Last edited: Nov 1, 2010
  6. fredj338

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    All good points. Once bullets get above 2000fps impact vel, they act diff when striking flesh. So a shallower depth may happen w/ certain 223 loads but the wound will be far greater in volumn. For handguns, as noted, you may have to shoot through add'l. body parts to get to vitals. A really big guy can have a forarm that is 6"-7" in dia. THat is taking quite a bit of steam off your bullets ability to get to the good stuff.
     
    #6 fredj338, Nov 1, 2010
    Last edited: Nov 1, 2010
  7. BOGE

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    Incorrect. How many times does this BS have to be quashed. :upeyes: The wound in question was mortal. It wouldn`t have mattered it was a .50 BMG as the perp in question was RESOLUTE and wanted to kill and adrenaline is an an amazing drug.

    It doesn`t matter if the bullet penetrates fully as the purpose of a gunshot wound is exsanguination (bleeding out), barring a CNS hit. You are diverting blood from its intended purpose. Nothing more, nothing less. If a person is bleeding into their own abdominal cavity from a gunshot wound it makes no difference if their are two holes or one. THE BLOOD IS NOT REACHING ITS INTENDED SOURCE, thereby shutting down the body (shock). Think about it.
     
  8. uz2bUSMC

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    How do they act different while at or above 2000fps?
     
  9. uz2bUSMC

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    Can you describe the difference in the character of work between the two? You've had Duncan's book for quite a few years now, have you managd to finally get through it? I know it took a couple of those years just to get half way. I'm listening...
     
  10. G31

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    481, I have never read the works you have cited, but have to ask a question. Do these works address bullet penetration, actual observed wound ballistics, or both?

    One problem I've seen with a strict math/science analysis is it puts too much emphasis on some of the smaller, less observable aspects of physics and what "should happen", rather than the actual observed (medically) reaction. For example, the idea that added energy transfer makes a difference in effectiveness between two different pistol rounds is valid in physics, but is unseen in the real world against humans. Same goes for almost all of the other theoretical influences brought by math/physics.

    Basically, I do not question the mathematical penetration information, as you can't outright defy physics, but would highly question the idea that any of the other info (if presented) translates to defensive/offensive use without any verified observation in the real world.

    Do these resources make conclusions to the effectiveness of bullets strictly using numbers?
     
  11. English

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    I do accept that my memory might be at fault and I have not read the report recently, but my memory was that a critical shot on one of the BGs stopped an inch short of the heart. This would have been a mortal wound but if it had penetrated the heart the BG would have been incapacitated within 15 to 30 seconds. As it was his relatively slow rate of exsanguination allowed him to get out of the car and work his way round behind what I think were two FBI agents who he killed. If the bullet had pentrated that extra two inches he could not have done this.

    English
     
  12. BOGE

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    English, write this down and remember it. The ME stated ON THE RECORD that the wound was mortal and the victim would not have survived had the wound ocurred in the best trauma center in the world. Some people just don`t want to die when we want them to.
     
  13. fredj338

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    I think the word is "eventually" fatal. Yes, Platt would have bled out, eventually. If the bullet went another 2", he would have bled out faster. It's not compeletly arbitrary; put a ruler across your chest from your shoulder, it's just about 12" to get penetration through the heart. At 10", my heart is still intact & I am in the fight longer, at 12" my heart has a very large hole in it & I am bleeding out sooner than later. One does not need to be a medical examiner to know that a big hole in your heart is better than just a hole in your chest cavity.
    Impact vel above 2000fps or so start to tear flesh through cavitation. There have been studies done by professional hunter in Africa on large game & when vel starts to matter w/ big bore rifles, most claim some place around 2000fps based on post mortem of the animal's tissue after the shot. Again, always assuming the bullet holds together to do damage & does not frag & lose penetration.
     
    #13 fredj338, Nov 1, 2010
    Last edited: Nov 1, 2010
  14. 481

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    G31,

    To varying degrees each of these works addresses both aspects.

    None of the three works cited above deviate into the needless pursuit of minutae from their objectives. All remain firmly focused upon the long proven disciplines of calculus, physics and (relatively simple) fluid dynamics.

    We can only measure that which can be measured. Intangibles are just that- intangible. Any attempt to quantify/qualify them is ill-advised and likely to make one a candidate for the Giggling Academy, if they are not one already.

    Nope.

    There is no way to quantify the phenomena that some refer to as "Stopping Power" (what units does "stopping power" or any other proposed construct claiming to define "terminal effectiveness" have?) in any meaningful, mathematical sense of the concept. Those who insist that there is are only displaying their resolute unwillingness to understand that there are far, far too many variables (which I will not even attempt to list here for my time's sake) involved in achieving the incapacitation of an assailant to do so.

    These works remain within the bounds of the disciplines and research mentioned above. No wild, speculative theorizing. Just quantitative modeling.

    Look 'em up. They are well worth the read!

    :)
     
    #14 481, Nov 1, 2010
    Last edited: Nov 1, 2010
  15. thegriz18

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    The point I am making is this.

    Vital organs don't change in distance between a rifle shot and handgun shot.
    Most .223 rounds penetrate 8-9 inches in bare gel, fragment with or without a barrier and we call them satisfactory rounds. Then we tell people that if a handgun bullet doesn't penetrate 12 inches it won't hit vitals, or at least not at a reliable rate. A .223 bullet will encounter the same barriers as handgun bullets, yet these bullets tend to fragment, we call them satisfactory and then moan about core/jacket separation in handgun bullets. I'm not saying the .223 is anemic, all I'm saying is calling 12 inches the minimum for a handgun and 7-8 inches the minimum for a rifle is stupid. We tend to discard handgun rounds that don't make 12 inches as failures, yet .223 rounds that make 8 inches pass. Can anyone else see how that makes zero sense?

    I'm simply questioning why there are two standards for each. Granted a rifle bullet will produce different damage than a handgun bullet, but shouldn't it be held to higher standards (or at least the same) than a handgun bullet?

    Perhaps we are wasting too much time with handgun bullets penetrating 12 inches when we should be spending time getting them to act like .223 rounds. Or maybe we should be making .223 bullets that don't fragment and stay together (Barnes TSX?). Which is it? Who is following my logic?
     
  16. English

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    I am glad for the confirmation that my memory was not at fault. The question is entirely one of time if we assume determination to keep fighting. With ones heart shot out, blood delivery to the brain ceases immediately but there is still enough blood in the brain and muscles to keep fighting effectively for 15 to 30 seconds according to the FBI. With a smalll hole through one wall of the heart that time might increase a little but most probably the heart will go into fibrillation and will not deliver any significant blood to the brain.. With almost any other gunshot wound which causes eventual death by exsanguination that time jumps to minutes and might be as long as 30 minutes but is still a mortal wound.

    What the FBI was looking for in its tests was a round with a greater probability of a faster incapacitation. I would guess that Platt's route from that wound to killing another agent was 4 or 5 minutes. If his heart had been punctured he would not have got there. Determination to keep fighting stops when you loose consciousness.

    English
     
    #16 English, Nov 1, 2010
    Last edited: Nov 1, 2010
  17. English

    English
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    griz,
    You mustn't say things like that. Some people will be very offended.

    English
     
  18. uz2bUSMC

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    I'm assuming that you are talking temporay cavitation. I'm gonna call cherry pick on this one Fred. Not because that's what you do, on the contrary, I've read enough of your post over the years to know that is not the case but because that sounds like the case here.

    2000 might be a good starting point for hardcast bullets which sounds about right for the an african study. I'm sure, because of a hardcast bullets profile, you will have to drive it fast to do damage via temp cavitation, however... this is not gonna hold true as a general rule of thumb. The rate of transfer is what will affect cavitation the most, i.e. a handgun bullet traveling @1700fps and penetrating only 10" may have greater temp cav than a hardcast rifle bullet traveling 2200fps which penetrates some 40" (because it doesn't deform). It's is all dependant upon the interaction of the projectile and the retarding forces, this interaction changes largely on rate of tranfer.

    You have a link to the study, or at least more info???
     
  19. uz2bUSMC

    uz2bUSMC
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    Griz,

    I'll tell it to you like this...

    People here have a hard time crossing thresholds. They like it to be "a rifle is a rifle and a handgun is a handgun". They can't keep simple things in perspective. An example... a while back I had suggested that a 10mm from a 6" bbl was roughly the same as 5.56 from a short BBL (which it is), and this caused a bit of a stink. The reason? 'Cause people don't want to accept that a pistol can do the work of a rifle. What you're asking is a taboo query... these people will discuss penetration depth adnauseum for pistols but breeze right by the subject with rifles because it is an uncomfortable posibility. You will see most "9 is fine" types in this kind of discussion.
     
  20. G31

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    I leave rifles alone, in general, because I don't know their ins-n-outs nearly as much as a handgun wound, so I tend to stay away from rifle ballistics when they get too in-depth. I do know a rifle bullet travelling at handgun speeds will act as a handgun round does, for the most part, but not due to observation, like I do a pistol wound.

    I do know there is a point where a round is powerful enough due to velocity to take advantage of energy dissipation, etc., but don't know the magic numbers associated with it.

    Under normal handgun velocities and energy numbers, I fall into the "9 is fine" group, as that is what medical science has shown to be as effective as any of the other defensive pistol rounds out there. If you had a .223 round going 1200 FPS, I doubt it would perform well at all. On the other hand, if a 9mm was pushed to rifle velocities, it would probably have a much better effect on the target.

    I guess I don't differentiate between types of firearms or rounds associated with them as a sweeping rule, so I could never fall into a "rifle is always better" crowd. It depends on wht the round can accomplish out of the gun it comes from.
     
    #20 G31, Nov 1, 2010
    Last edited: Nov 1, 2010
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