Knockdown Power?

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JohnKSa

JohnKSa

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Those of you who already know it's a myth can stop reading here. (Unless you just want to enjoy seeing stuff shot with a really big rifle.) :D

This is a video of Jerry Miculek "testing" some body armor with a .50BMG rifle.



A suspended crash test dummy (partial dummy--no lower arms or legs), equipped with an armor plate is shot at about 20 yards with a 50BMG. The 750 grain bullet stopped in the armor so every bit of the momentum (roughly 10 times more than a .45ACP round) was transferred to the dummy. You can see for yourself how much (or how little) the impact causes the dummy to move.

The shock of being hit will likely cause a person to react, but it's quite obvious that the impact/momentum alone, even from the mighty .50BMG isn't going to knock someone down.
 
IMO, it's a bit of a misnomer, but it's a term of convenience. What would you have us call it?
 
Since it clearly doesn't exist, maybe we shouldn't call it anything at all. Just a thought...:D

Seriously, although most serious shooters probably know that anything that one person can carry and shoot that doesn't send an explosive charge downrange won't knock a person down, the movies work so hard to perpetuate the myth that many people do believe it. When we use the term (knowing it's not accurate) we also help perpetuate the myth which is the opposite of what we, as experienced and responsible shooters should be doing.

Also, based on what I read on the forums, even some shooters who should know better still seem to believe that the force of a bullet impact can knock someone down. And other shooters think that while some bullets and calibers have the ability to knock someone down, others simply can't--that there's a practical difference in "knockdown power".

I see it all as part of an unhelpful mentality that places more emphasis on bullets and calibers and guns and deflects away from the truly important aspects of handgun self-defense. I posted my own personal definition of Caliber War on THR awhile back--one part of it says that a Caliber War is a discussion in which people who really know the truth about what wins gunfights pretend instead that you can buy it in boxes of 50 from the gun store--and argue about what markings should be on the box.

It struck me that perhaps I was being overly optimistic about what people know or don't know about what wins gunfights and I figured that clarifying the misconceptions about "knockdown power" might be a good place to start.
 
#1 you can't knock over a target that is hung by the top. You can make it swing but that is about it.

#2 The round did not penetrate but is wasn't a military round. Try 50BMG AP.

#3 Even if it doesn't penetrate is will crack ribs on the other side. Guy will be down and out of the fight.

 
I have a bone to pick with shooting the BMG in a 20" barrel.:( Velocity with 750 A-max is probably struggling to hit 2200 fps so this is really throttling the cartridge down to almost black powder levels. It's like putting a two barrel carb on a 454....yes, you ARE driving a Big Block but it's so choked that it's not putting out what the name implies.
 
IMO, an even worse term is "bullet-proof vest". The average person has no idea the blunt
trauma stopping a bullet with your body causes, even with a good vest. They just think
you strap on a vest, and bullets are going to magically bounce off.

But Myth-Busters did "knockdown power" to death. Basically, no such thing. Unfortunately,
every time somebody does a movie like Last Man Standing, the myth grows.
 
Dibbs said:
IMO, an even worse term is "bullet-proof vest". The average person has no idea the blunt
trauma stopping a bullet with your body causes, even with a good vest. They just think
you strap on a vest, and bullets are going to magically bounce off.

But Myth-Busters did "knockdown power" to death. Basically, no such thing. Unfortunately,
every time somebody does a movie like Last Man Standing, the myth grows.
Click to expand...
That's the film I always think of in this topic. Absolutely ridiculous portrayal.
 
Well, getting hit like that would probably knock you out if hit in the right spot but for sure break a few ribs. Still much better than your body parts being spread all over the hill if not with a 50 and no armor. That armor is extremely impressive!
 
Gun magazine writers have been perpetuating this myth for decades.

Read any of them and sooner or later, you will read about handgun "knockdown power."
 
Having worn a lot of hard armor in my career, I’m incredibly impressed with that armor.
 
#1 you can't knock over a target that is hung by the top. You can make it swing but that is about it.
Click to expand...
Right. The point is you can look at how little it swings and get a feel for what's going on in terms of momentum transfer.

If the hanging dummy is really a showstopper for you, Mythbusters did a similar test where they used a .50BMG rifle to shoot a carefully balanced dummy that could actually be knocked down. As in this test, the bullet was stopped in the dummy--they used a steel armor plate and the steel spine of the dummy caught the damaged bullet after it penetrated the plate. The dummy was dislodged from its precarious supports and fell mostly straight down. Even in the slow motion it was obvious that the dummy was barely knocked backwards at all.

Here's a post I made with screen captures from that test.
https://www.thehighroad.org/index.php?threads/knockdown-power.833095/page-3#post-10777900
#2 The round did not penetrate but is wasn't a military round. Try 50BMG AP.
Click to expand...
Had the round penetrated, it would have exited with some of its initial momentum. That would mean LESS momentum would have been imparted to the target and it would have made the target swing even less.
#3 Even if it doesn't penetrate is will crack ribs on the other side. Guy will be down and out of the fight.
Click to expand...
1. It's a crash test dummy. It wasn't fighting, it was just hanging there. :D
2. This type of plate is usually worn with some sort of padding behind it. But you would certainly feel it even if it didn't break ribs. HOWEVER...
3. The point wasn't about whether or not bullets can end fights, it was about the ability of bullets to knock people down by their impact force.
I have a bone to pick with shooting the BMG in a 20" barrel.:( Velocity with 750 A-max is probably struggling to hit 2200 fps so this is really throttling the cartridge down to almost black powder levels.
Click to expand...
Ok, I'm going to assume that the comment about "black powder levels" was intended to be humorous and take it in that vein.

Miculek states in the video that the velocity is about 2400fps which would mean that it has only 9 times the momentum of the 45ACP instead of about 10 times :D. I don't think that really changes anything in terms of the main point--which is that if something with many times more momentum than the 45ACP only makes a lightened crash test dummy swing a little bit, no handgun round is going to come even close to knocking someone down.

There is NO knockdown power folks. Certainly not from handguns and not even from rifles. None. If you can carry it and fire it and it doesn't send an explosive charge downrange it won't knock a person over from the force of the impact.

Still having trouble? Here's a video that shows a person standing on one foot can soak up a .308 rifle round without falling over.

 
I think you are all misinterpretating the intended meaning of knockdown power. If you hit someone center mass with that bullet, you will put them down. You will injure them so badly they can’t stand most likely ever again. That is a knockdown to me. Who cares if the bullet force doesn’t knock an inanimate object down?
 
rpenmanparker said:
If you hit someone center mass with that bullet, you will put them down. You will injure them so badly they can’t stand most likely ever again.
Click to expand...

This simply isn't true. The majority of people who are shot with a handgun survive the experience. At the North Field, Minnesota bank robbery Thomas Coleman Younger was hit eleven times with rifle bullets and managed to ride out of town and survived for several years afterwards dying of old age
 
Trunk Monkey said:
This simply isn't true. The majority of people who are shot with a handgun survive the experience. At the North Field, Minnesota bank robbery Thomas Coleman Younger was hit eleven times with rifle bullets and managed to ride out of town and survived for several years afterwards dying of old age
Click to expand...
Sure it’s true. Multiple anecdotes do not constitute data. We aren’t specifically talking about kills. That was just a side comment I made. We are talking about center mass hits putting someone off their feet due to some level of damage, not due to brute force. So let me ask you this: if your thesis is correct what is even the point of this entire website? Guns don’t injure and maybe kill people, right? So why do cops carry them, the FBI, soldiers, etc., etc. ? What are we all doing here?
 
rpenmanparker said:
Sure it’s true. Multiple anecdotes do not constitute data.
Click to expand...
LOL! Seems you could make the same assertion about the generalization you just made. There are plenty of stories out there with one shot stops to center mass and plenty where center mass hits did not stop the threat immediately. We train as if they will be ineffective so WE are effective.

Knockdown power refers to the false phenomenon of an impacting bullet knocking someone or something off its feet. Physics prohibit this. While a bullet may impart many hundreds of foot pounds of energy, the focal point is so small and the anchoring mass of a living body proportionally so much greater that a bullet penetrates. This is why riot police use beenbags at low velocity to disperse rioters.

I agree with JohnKSa. Knockdown power is a false phenomenon proliferated by Hollywood and ignorant authors.

The ability of a bullet to crippled a living creature and inhibit its ability to move on its own two feet is a different topic.
 
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rpenmanparker said:
Sure it’s true. Multiple anecdotes do not constitute data. We aren’t specifically talking about kills. That was just a side comment I made. We are talking about center mass hits putting someone off their feet due to some level of damage, not due to brute force. So let me ask you this: if your thesis is correct what is even the point of this entire website? Guns don’t injure and maybe kill people, right? So why do cops carry them, the FBI, soldiers, etc., etc. ? What are we all doing here?
Click to expand...

So, let's take a look at what you claimed

rpenmanparker said:
If you hit someone center mass with that bullet, you will put them down. You will injure them so badly they can’t stand most likely ever again.
Click to expand...

You even clarified that they will be so badly injured that they will most likely never stand up again.

rpenmanparker said:
You will injure them so badly they can’t stand most likely ever again.
Click to expand...

Again, most people shot with handgun bullets do, in fact, stand up again. They do survive and they do go on to live long lives after being shot.

There's a reason that most people train to shoot multiple times. There's a reason that most reputable trainers teach their students to continue to engage until the assailant is no longer a threat.

The fact is that a large portion of the time getting shot doesn't initially change the behavior of the person being shot. People continue to attack with bullet holes in them every day.
 
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rpenmanparker said:
I think you are all misinterpretating the intended meaning of knockdown power. If you hit someone center mass with that bullet, you will put them down. You will injure them so badly they can’t stand most likely ever again. That is a knockdown to me. Who cares if the bullet force doesn’t knock an inanimate object down?
Click to expand...

rpenmanparker, I also look at “knockdown power” the same way. Perhaps “one shot stop” is more accurate, but then that term opens cans of worms as well. :)
 
460Shooter said:
LOL! Seems you could make the same assertion about the generalization you just made. There are plenty of stories out there with one shot stops to center mass and plenty where center mass hits did not stop the threat immediately. We train as if they will be ineffective so WE are effective.

Knockdown power refers to the false phenomenon of an impacting bullet knocking someone or something off its feet. Physics prohibit this. While a bullet may impart many hundreds of foot pounds of energy, the focal point is so small and the anchoring mass of a living body proportionally so much greater that a bullet penetrates. This is why riot police use beenbags at low velocity to disperse rioters.

I agree with JohnKSa. Knockdown power is a false phenomenon proliferated by Hollywood and ignorant authors.

The ability of a bullet to crippled a living creature and that nhibit its ability to move on its own two feet is a different topic.
Click to expand...
Exactly. We agree completely. I’m just muddying the water.
 
JohnKSa said:
Miculek states in the video that the velocity is about 2400fps which would mean that it has only 9 times the momentum of the 45ACP instead of about 10 times :D. I don't think that really changes anything in terms of the main point--which is that if something with many times more momentum than the 45ACP only makes a lightened crash test dummy swing a little bit, no handgun round is going to come even close to knocking someone down.
Click to expand...
You're dead right.

Let me point out this is a 750 grain bullet at 2400 fps. A .458 Lott will deliver a 500 grain bullet at 2300 fps. That's a BIG difference in momentum over one of the most powerful "elephant rifles" in existence.
 
When people talk about “knockdown power” I’m not sure they mean that the force of the bullet is actually going to knock them over... IF that’s what they mean, well, that’s dumb. But I don’t think it is, generally.

And ironically, in real life, anyone getting hit with 750gr projectile at 2400 fps is going down. Straight down. Call that what you want, or nothing, bullet proof vest or not;)
 
I will preface this I don't believe in "knock-down power" as the movies might portray it. ie sending the target fly.

Let also assume that in the next paragraph there in no CNS interruption.

Now imagine your walking along nice and relaxed, peaceful like, totally lost in your own thoughts and not on your guard. Along comes someone that sneaks up behind you and hits you in the shoulder or ribs with roughly the same momentum change as the recoil of your favorite center-fire rifle or shotgun you might use for deer or elk hunting, completely and totally unexpected. I suspect most people would be knocked down. Not because the momentum change knocked you off your feet movie style but simply because the momentum change happened unexpectedly enough and at an odd enough direction that it disrupts your gate and balance faster than you can react. I am sure some exceptionally agile people might remain standing. Depending on where in a step you are (ie both feet on the group, one foot in the air etc) might have a better or worst chance of keeping your feet. So some of the "knock down" is not from the raw momentum change. As we all know a bullet impact (momentum transfer) can't be as great as the recoil the shooter felt firing it. The fact that it comes unexpected at a point and direction the target did not anticipate makes it more effective then the raw momentum numbers might indicate.

Couple that with raw tissue damage (especially structural damage to bone) and possible partial nerve damage in the impacted area or even CNS damage and you get real world knock-down power.
 
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