Knock down power

Knock down power

This is a discussion on Knock down power within the General Firearm Discussion forums, part of the Related Topics category; I found this to be a very interesting and informative read. Handgun Wounding Factors and Effectiveness A bullet simply cannot knock a man down. If ...

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Thread: Knock down power

  1. #1
    Senior Member Array Andy W.'s Avatar
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    Knock down power

    I found this to be a very interesting and informative read.
    Handgun Wounding Factors and Effectiveness

    A bullet simply cannot knock a man down. If it had the energy to do so, then equal energy would be applied against the shooter and he too would be knocked down. This is simple physics, and has been known for hundreds of years.31 The amount of energy deposited in the body by a bullet is approximately equivalent to being hit with a baseball.32 Tissue damage is the only physical link to incapacitation within the desired time frame, i.e., instantaneously.
    My son and I have had this discussion before, I disagreed with him. It turns out he was right all along.


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    VIP Member Array Rob72's Avatar
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    If that were true, neither could a ball bat. "Structural insult"- a mechanism can only withstand so much interruption of its necessary function before ceasing function. No, you won't spin 200# out of a chair with your .45, but you might easily knock a 200# man out of a chair with a shot to the head, scapula, or sacrum.

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    Definition of "knock down"

    One problem here is that "knock down" is not a very precise term. If a person crossing a road is struck by a car going 20 mph, it will certainly knock him off his feet. A 4000 pound car going 20 mph has a lot of momentum (mass times velocity), and could easily tip over a 180 pound person.

    A half ounce bullet going 900 fps has much less momentum than the car, and probably wouldn't knock the person off his feet. However, the bodily damage caused by the bullet could cause the person to fall down. But that would be a little different than being "knocked down", I think

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    "Mythbusters" did a great job on one of their shows proving that "knockdown" power was a myth...they showed a huge hunk of meat being hit with various bullets. Funny, it didn't fly backwards like they show in the movies...all kidding aside, it's just a physics thing.
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    Oh my goodness did I have one heck of an argument with someone about this very same thing.

    The general agreement is that while certain bullets CAN knock people down they are fired in such a way that the shooter is prepared for the energy of the weapon by either laying down themselves or positioning them self in a way that ensures they will remain standing as their opponent goes down due to lack of preparation for getting hit with a bullet.

    Most of time gunshot victims fall, not from the force of the bullet but from damage caused by the bullet, the psychological effects of knowing you are shot or death.

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    Quote Originally Posted by Kompact9 View Post
    "Mythbusters" did a great job on one of their shows proving that "knockdown" power was a myth...they showed a huge hunk of meat being hit with various bullets. Funny, it didn't fly backwards like they show in the movies...all kidding aside, it's just a physics thing.
    What? Hollywood wouldn't lie like that. Now I know they do lots of research and would only portray factual data.

    Kidding aside, there are a lot of people that get too many "facts" from movies and such. It's amazing how many times we (in my job) have had to tell people that CSI is "a TV show".
    eschew obfuscation

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    Senior Member Array Andy W.'s Avatar
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    The article states that permanent wound cavity size and penetration are key to effectiveness. If that is so, are you better off with FMJ as opposed to hollow point?

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    JD
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    Quote Originally Posted by Andy W. View Post
    The article states that permanent wound cavity size and penetration are key to effectiveness. If that is so, are you better off with FMJ as opposed to hollow point?
    FMJs would cause a smaller wound cavity, due to lack of expansion.

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    VIP Member Array Cupcake's Avatar
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    Quote Originally Posted by JD View Post
    FMJs would cause a smaller wound cavity, due to lack of expansion.
    Correctamundo, and FMJs actually make a smaller wound cavity thatn their diameter due to tissure just strectching/slipping around the smooth nose. I like some nasty sharp jagged HP slicing its way through whoever needs it.

    As for "knock down power" Sever the spine with good shot placement.
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    Senior Member Array cockedlocked01's Avatar
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    It also depends on mindset. I've seen/read/heard where people literally drop thinking they'd been shot (Or just wounded), then others that just keep coming (At least until they bleed out or a major organ that's been shot shuts down). Of course, certain chemicals ingested by the person could replace mindset.

    Having said all that, a handgun round is relatively minor compared to rifle rounds. A handgun round out of a rifle is a step up, but even that's not going to generate as much force as a rifle round traveling at 1.5-2Xs the handgun round.
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    Senior Member Array Andy W.'s Avatar
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    It also depends on mindset
    The article discusses this as well. Has anyone read the article? It goes into great detail on these issues.

    The tissue disruption caused by a handgun bullet is limited to two mechanisms. The first, or crush mechanism is the hole the bullet makes passing through the tissue. The second, or stretch mechanism is the temporary cavity formed by the tissues being driven outward in a radial direction away from the path of the bullet. Of the two, the crush mechanism, the result of penetration and permanent cavity, is the only handgun wounding mechanism which damages tissue.23 To cause significant injuries to a structure within the body using a handgun, the bullet must penetrate the structure. Temporary cavity has no reliable wounding effect in elastic body tissues. Temporary cavitation is nothing more than a stretch of the tissues, generally no larger than 10 times the bullet diameter (in handgun calibers), and elastic tissues sustain little, if any, residual damage.24,25,26
    According to the article, the temporary cavity doesn't do much.
    Last edited by Andy W.; June 11th, 2007 at 02:32 PM.

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    Senior Member Array Andy W.'s Avatar
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    Quote Originally Posted by JD View Post
    FMJs would cause a smaller wound cavity, due to lack of expansion.
    I agree, but this guy is claiming expansion occurs about 60-70% of the time at best. According to this article, I wonder if a FMJ may be better (especially in a smaller caliber) to achieve penetration. The reason I'm asking these questions is because it goes against a lot of what I've believed to be true.
    Expansion accomplishes several things. On the positive side, it increases the frontal area of the bullet and thereby increases the amount of tissue disintegrated in the bulletís path. On the negative side, expansion limits penetration. It can prevent the bullet from penetrating to vital organs, especially if the projectile is of relatively light mass and the penetration must be through several inches of fat, muscle, or clothing.34

    Increased bullet mass will increase penetration. Increased velocity will increase penetration but only until the bullet begins to deform, at which point increased velocity decreases penetration. Permanent cavity can be increased by the use of expanding bullets, and/or larger diameter bullets, which have adequate penetration. However, in no case should selection of a bullet be made where bullet expansion is necessary to achieve desired performance.35 Handgun bullets expand in the human target only 60-70% of the time at best. Damage to the hollow point by hitting bone, glass, or other intervening obstacles can prevent expansion. Clothing fibers can wrap the nose of the bullet in a cocoon like manner and prevent expansion. Insufficient impact velocity caused by short barrels and/or longer range will prevent expansion, as will simple manufacturing variations. Expansion must never be the basis for bullet selection, but considered a bonus when, and if, it occurs. Bullet selection should be determined based on penetration first, and the unexpanded diameter of the bullet second, as that is all the shooter can reliably expect.

    It is essential to bear in mind that the single most critical factor remains penetration. While penetration up to 18 inches is preferable, a handgun bullet MUST reliably penetrate 12 inches of soft body tissue at a minimum, regardless of whether it expands or not. If the bullet does not reliably penetrate to these depths, it is not an effective bullet for law enforcement use.36

  13. #13
    JD
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    I agree, but this guy is claiming expansion occurs about 60-70% of the time at best. According to this article, I wonder if a FMJ may be better (especially in a smaller caliber) to achieve penetration. The reason I'm asking these questions is because it goes against a lot of what I've believed to be true.

    There's a few things wrong here.


    Increased bullet mass will increase penetration.
    Your wondering if a smaller bullet will achieve more penetration, but thge staments in BOLD above and below negate that.

    Increased velocity will increase penetration but only until the bullet begins to deform, at which point increased velocity decreases penetration.

    Below it states that larger diameter bullets which have adequate penetration can increase the cavity. This rings true.
    Permanent cavity can be increased by the use of expanding bullets, and/or larger diameter bullets, which have adequate
    penetration
    .

    Reading below, goes into the 9mm vs .45 dsebate (LETS NOT GO INTO THIS AGAIN PLEASE)

    Most 9mm fans are only 9mm fans due to modern JHPs, IMHO
    a 9mm or other "small" FMJ projectile would not be in keeping with below, I would not choose a smaller FMJ becsue in SD situations, realisticly you want to do as much damage as you can with as few shots.

    However, in no case should selection of a bullet be made where bullet expansion is necessary to achieve desired performance
    If a .40 or.45 doesn't expand it's still .40 or .45, thus giving you a larger projectile to accomplish the following from above:


    Increased bullet mass will increase penetration.
    Permanent cavity can be increased by the use of expanding bullets, and/or larger diameter bullets, which have adequate
    penetration
    .
    In summary, expansion is a requirement in self defense situations.

    Further more:

    1: A larger slug will casue a larger cavity.

    2: While a smaller slug will have more velocity, once it starts to deform velocity is the ememy (or so it seems from the quote)

    3.Permanent cavity can be increased by the use of expanding bullets, and/or larger diameter bullets, which have adequate penetration.

    So if you have a higher velocity, larger sized JHP like a .40 (larger than a 9mm, more velocity than a .45 IIRC) or a .45+P your all set, who cares if it doesn't expand?

    The Military uses smaller FMJ rounds based on the theroy that if you wound one enemy it will take two to aide him. That and JHPs are banned my the Geneva Convention.

    In a SD situation, your not trying to wound, your trying to quickly and effeciantly negate a threat.

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    VIP Member Array obxned's Avatar
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    So much for the 'magic bullet' school of thought.
    "If we loose Freedom here, there's no place to escape to. This is the Last Place on Earth!" Ronald Reagan

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    Senior Member Array Andy W.'s Avatar
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    The Military uses smaller FMJ rounds based on the theroy that if you wound one enemy it will take two to aide him.
    That's what I've heard too.

    I agree that if a 45 doesn't expand, big deal. It makes a big hole. The article suggests a bullet that will penetrate a minimum of 12" of body tissue. I was wondering if in a 9mm or 380 hollow point would do that due to velocity loss caused by expansion. I don't want to start a 9mm vs 45 debate either, that horse has been beaten to death.

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