Knockdown Power

[USMC 82-86]

I knew my right cross had more knockdown power than a measly .45.

[Creampuff]

True, true.
But an 80mph Fastball, cannot penetrate my body and lodge itself into the CNS, which could result in an instant knockdown.

Well, unless the fastball hit me right in the temple...umm never mind.

This is too cerebral the night before Thanksgiving. I'm going to go back to watching Woody Woodpecker with the kids.

[jumbopanda]

Guns are meant to punch holes in people, not knock them down. If you want to knock someone down, get a baseball bat.

If you're worried about the effectiveness of a firearm in an self defense scenario, I'll make things simple for you. Just ask yourself two questions:

1. Will this gun penetrate enough tissue to reach vital organs?
2. Will I be able to shoot an assailant in a vital organ?

[IVC]

You have to define the "knockdown power" before you make any comparisons.

From the physics perspective, you would most commonly talk about either (1) momentum, or (2) energy, or (3) pressure on impact. These are vastly different concepts and comparing them to a baseball ball is at minimum misleading.

Look at momentum first. If you wore a steel plate and got hit by the bullet, you would feel the same as if you got hit by the baseball of the appropriate velocity. Neither would hurt and you wouldn't fly off. But, this is not how the things work.

What matters is the surface area of the projectile, since the pressure at the impact point is inversely proportional to this area. That's why if you get hit behind a steel plate, you feel nothing (very low pressure, since force is applied over large area). If you get hit with the bullet directly, the pressure is so large that it will penetrate your body. This is significantly different than the baseball which has large surface area (due to softness of the body, the area of contact is quite large).

The penetration is what starts the killing process. Once inside the body, the energy starts dissipating while the bullet is traveling through the body and causing damage. At this time, hollow points will expand to ensure (1) larger cavity with potential for bleeding; (2) all energy is used up for causing internal damage by effectively coming to rest inside the body, having shed all of the kinetic energy.

The energy dissipation inside the body is also why FMJ bullets are not suitable for hunting. If there is no direct hit to a vital area, FMJ will travel through the body and exit, having caused very little damage except in the direct path of the bullet.

Take all of this into account and you'll see that it's pretty naive to compare bullets to baseballs. You can match the momentum, but you completely miss the mechanism that causes damage.

[therealnickb]

This topic comes around now and then and I've read several threads, but I just thought of a new way to think about it that makes sense.

I've read enough threads and done some calculations, to say that a 45 acp has knockdown power similar to an 80 mph fastball... which isn't that much "knockdown power". Knockdown power is generally a myth.

The new way to think about it though is "for every action, there is an equal and opposite reaction". If you fire a weapon that knocks you back on your butt, then yes, that probably has some real "knockdown power". But that's going to be something like an elephant gun, that is hard to manhandle the kickback.

Just thought I'd share. Knockdown power makes more sense to me thinking about it that way. Cheers!

reel reel reel reel player?

[therealnickb]

Guns are meant to punch holes in people, not knock them down. If you want to knock someone down, get a baseball bat.

If you're worried about the effectiveness of a firearm in an self defense scenario, I'll make things simple for you. Just ask yourself two questions:

1. Will this gun penetrate enough tissue to reach vital organs?
2. Will I be able to shoot an assailant in a vital organ?

guns don't penetrate.

[therealnickb]

When you fire your 45 acp gun, you already have a firm grip on the handle.

When you catch the 80mph fastball, you have to eliminate the sting and focus only on how much push force you got from catching it. That's the knockdown power.

1) with a mitt.

2) I've never been "knocked down" by anything smaller than a human.

[ClarenceBoddicker]

Actually, hollow points could enhance knockdown power. A hollow point will transfer most if not all of it's momentum into it's target. A standard round nose projectile will likely exit it's target out the back and not transfer all it's momentum into the target.

No, as knockdown power from guns that can be fired with a human holding them does not exist. The projectile would have to weigh very close to the target to be able to knock them down.

A hollow point round can certainly enhance stopping power, which is very real unlike knockdown power.

[POLICESTATE]

About a year ago I ran a poll over which round would people least like to get hit by, .45 ACP, .40 S&W, 9mm. .45 won of course, followed by the .40 and finally the 9mm last. It was done to end the whole "9mm vs .40 vs .45" debate going on at the time. Yeah it was kind of silly but the fact is, you are more likely to get more damage out of a .45 than a 9mm. Also we see the same thing with 5.56mm vs 7.62mm.

In any case, I would much rather take an 80mph baseball to the chest than a .45 ACP to the chest. There is no comparison. One is going to hurt, the other will very likely kill me, or at least come very close.

Strange observations you make there Marthor. Out of curiosity, how do you answer question 11.f. on the ATF Form 4473?

Oh and I should point out that the size of objects in motion and their mass in addition to velocity make a huge difference in what happens when they hit other objects.

A baseball is not a bullet.

[patriot_man]

So what you're saying is that the energy exerted by a 80 MPH baseball is comparable to the energy exerted by a .45 ACP round?

I'd take a 80 MPH baseball any day over .45 ACP. Quick calculation with a 145 gram baseball at 80 MPH comes out to around 117 Joules, nothing in comparison with any .45 ACP round.

[jumbopanda]

guns don't penetrate.

[SB1964]

I`ve never Caught a .45 ACP!

[Marthor]

Take all of this into account and you'll see that it's pretty naive to compare bullets to baseballs. You can match the momentum, but you completely miss the mechanism that causes damage.

We didn't miss anything. As was said earlier, the topic of this thread is "knockdown power".

When comparing the baseball and bullet, we're only talking about knockdown power. We're not talking about penetration or which one does more damage. The 45 acp bullet and baseball both have very small "knockdown power".

[the86d]

If you are looking for knockdown power, you should keep cinder blocks near the top of the stairs...

[FX-05 Xiuhcoatl]