What is "Knockdown"?

[Excaliber]

Again...I don't think it would be enough to knock the shooter down...but it would be closer.

The FBI took this into account.

What the FBI said is that the total energy developed by the cartridge is nowhere close to the amount of energy required to knock a man down. Energy that is absorbed by the wrists, elbows, etc. still was transferred to the shooter who those wrists and elbows are attached to.

In an effort to put the situation into simple terms, the FBI also stated that the terminal energy dump of a handgun bullet was about the same as getting hit with a baseball. Like in the case of handgun bullets, people hit with baseballs sometimes fall down, but not because of the kinetic energy transfer from the impact.

[srothstein]

Well, I was going to leave this alone, especially since I agree that, as a general rule, a bullet cannot knock a man down. But, I decided to throw some fuel on the fire.

A bullet can knock a man down through the means of knocking him off balance. A standing man is really a fragile balance sometimes, and a properly placed round can knock him to the ground.

For example, when I was talking about the Mozambique drill, I pointed out that a shot to the hips could help bring a man down by moving the hips out from under him or by breaking the support structure holding him up. A round in the ankle that could knock the leg out from under a man and also knock him down.

And, for anyone who thinks the rules of physics are stopping the person from being knocked down, I will ask them if they have ever been in a fight and pushed someone. I have pushed people and knocked them down that way, and seen people knocked down by a well thrown punch. In neither case did the person exerting the force fall.

In the case of the fighter, as in the case of a bullet, the factor of balance must not be ignored. A bullet can knock a man down, but it is not just a matter of the physics. In addition to balance, there is a matter of the shooter being braced for the force and the recipient not being braced. That makes the amount of force necessary different for each person, as does the size of the shooter compared to the size of the target.

Knockdown power is many things, including the wound effects and shock of the bullet. It is not just the transfer of energy or momentum and not simple physics.

[TexasComputerDude]

I say we submit this to mythbusters.......

[jimlongley]

I say we submit this to mythbusters.......

OK, this is getting way too circular - I refer back to the second post where Mythbusters already took a look at the issue.

As has been posted, simple physics tells us that the huge effect portrayed in fiction is just flat not going to happen, but it also tells us that, like a bowling pin pushed past 15 degrees won't stand up again no matter how long it totters, if a person is just off balance enough at impact it may aid in pushing them past the equilibrium point - and that's it.

[Excaliber]

if a person is just off balance enough at impact it may aid in pushing them past the equilibrium point - and that's it.

Both jimlongley and srothstein are of course correct - any energy transfer, from a bullet, a baseball, or anything else, can cause a sufficiently weakly balanced object (or person) to tip over. The source of the energy is irrelevant to the effect. This is much different than the concept of "knockdown", which is generally taken to mean the ability to knock a standing man off his feet most or all of the time.

The FBI did not say that a person will never fall when struck by a handgun bullet. What they did say is that handgun bullets do not transfer enough kinetic energy to consistently knock a standing man down.

Even two shots are so often not enough to end an attack. The fact that one shot knockdowns are the exception rather than the rule is why current law enforcement, military, and civilian self defense doctrine has changed from "fire two shots into the center of mass and assess" to "continue to shoot until the threat is no longer a threat."

The takeaway is: If you happen to shoot a very weakly balanced assailant (these are a bit rare, but I suppose they're out there somewhere) and he happens to fall down after your first shot, you're having a very good day. Just don't count on it happening so you won't be surprised or disappointed when it doesn't.

[TexasComputerDude]

well, I just wanted to see them blow more stuff up.....

but no my bad for forgetting it was posted earlier, I just clicked the last page every time I checked this post.

[Skiprr]

OK, this is getting way too circular...

Wait! I think Jim has it!

If you whip your arm around as you fire, you can add add momentum to the bullet, make it curve around an object, all sorts of things...
[youtube]http://youtube.com/watch?v=p_p9VIBYo1E[/youtube]



Seriously, though, I think we all pretty much agree that this a non-issue for civilian weapons. Sure-fire knockdown power on the street is having two or three, trained, ex-NFL, 330-pound personal bodyguards at your command; together, they should be able to knock down just about anybody.

[Mike1951]

If you whip your arm around as you fire, you can add add momentum to the bullet, make it curve around an object, all sorts of things...

Similar technique to the flinging of bullets out of a 72-shooter in the westerns that we grew up watching.

You just knew that the 'flinging' must have added great force to the bullets.

[WildBill]

Similar technique to the flinging of bullets out of a 72-shooter in the westerns that we grew up watching. You just knew that the 'flinging' must have added great force to the bullets.

The scary part is that these same people could be on your jury thinking you should have shot the gun out of the BGs hand.