Is there such thing as "knock down power"?

[Stinkyshoe]

I have heard it both ways. I wonder if the term wasn't coined by a firearms retailer, rather than by someone with ballistic knowledge. Is there such thing as "knock down power". I guy I know swears the FAL has more "knock down power" than the AR-15. I know another guy I know who is a Swat Cop and a professional firearms trainer who says that "knock down power" is a myth. He said people fall over after being shot because they see thats what happens on TV. He said thats why deer run when shot, because they don't know they've been shot. He also commented about people who say that the 45 acp has so much more "knock down power" than a 9mm. He said he prefers the 9mm and emphasized being proficient with the gun, and spending for shooting classes, rather than inmaterial accessories. Anyways, Please help demystify my confused brain.
Thanks
Ss

 

[Preacherman]

"Knock down power" is a myth spread over many, many decades (centuries!) of firearms use. The power of a given bullet is a function of its weight and velocity, measured in terms of its kinetic energy. If it hits something, some or all of that energy is transferred to what it hits. If it's a bullet hitting an animal (or a human being), its design will determine how much energy is transferred to its target. A full-metal-jacket, non-expanding bullet will drill a narrow hole straight through, and probably exit (except for low-power handgun rounds). A hollow- or soft-point bullet will expand, greatly increasing the speed of deceleration, and may or may not over-penetrate, depending on mass, velocity and target thickness and density.

All of the energy transferred to the target disrupts tissue and/or breaks bone. If sufficient energy is transferred to muscle tissue, a violent, spasmodic reaction can occur, which can lead to the target falling over. This is NOT the bullet "knocking down" the target, but a muscular reaction. On the other hand, if a major bone structure is broken, it may well be that the body can't remain standing due to a lack of sufficient support structure. Again, it's not the bullet knocking the target over: it's that the target is no longer able to support its own weight.

Other factors leading to the target falling over can be instant cessation of nervous system function (e.g. a brain or spine shot), or the cumulative effects of bleeding (i.e. oxygen starvation affecting the brain and/or muscles).

A sufficiently heavy "punch" from a major caliber can give the impression of knocking a target over: but this is NOT the case. If you look up the momentum (mass multiplied by velocity) of the bullet, and compare it to the momentum of the target, you'll see that the first is usually insignificant compared to the second. (I'm not talking about varmint hunting, where a .223 hollowpoint can send a groundhog flying through the air, of course! I'm talking about deer and/or human targets, which are pretty similar in weight.)

Hope this helps...

 

[BigG]

Yes, but it's usually provided by a large, flattish, heavy object like a brick or a cement block. My understanding is the heavier, larger bullets provide more of whatever bullets do, but knockdown power is largely gunwriter hype.

 

[priv8ter]

Hmmmm...

I'm sure this is going to be a lively topic...

I think pretty much all of usare agreed that most of your defensive pistol loads lack true 'knock down power.

But, rifles are different story in my humble opinion.

9mm and .45 loads are talked about in terms of hundreds of foot-lbs. Some of your higher energy hunting loads can be talked about in TONS of foot-lbs.

Where I think knock-down power comes into effect is how effeciently that energy is transfered into a target. Are you using a 55gr .223 FMJ that enters the target at 3000 FPS, and exits the other side at 2700 FPS, or 300gr .45-70 load that enters the target at 2200 FPS and stays there?

This is that other controversial topic known as Energy Dump.

As for deer walking away, that is true, I have seen it happen. I have seen more than one deer and elk dropped right in their tracks by a well placed .30-06 or .270 with good, fast expanding bullets.

Your friend is right about the following though:

emphasized being proficient with the gun, and spending for shooting classes, rather than inmaterial accessories

I don't think there is a person out there who will disagree with that.

greg

 

[redneck]

According to basic physics....NO! there is no knockdown power, for the most part. The powder expands as it burns pushing in all directions, the barrel contains the pressure to a linear path and the bullet moves down the barrel accelerating. There is an equal amount of force pushing the gun backwards as there is pushing the bullet forwards. The gun is heavier and doesn't accelerate as much, and the force is exerted on you over a much larger area due to the stock design, but basically in order for the bullet to have "knockdown power" the recoil would have to be powerful enough to knockover the shooter. That negates pretty much anything but artillery from having "knockdown" power.


OR

You can look at it from a less literal point of view. Some chamberings do have a much greater potential for putting something down and out of the fight. A 12 guage slug for example, does a massive amount of damage, and carries a pretty substantial punch as attested to by the shove you get from the recoil. It has a very good potential for putting someone on the ground when you combine the shock of being hit, the damage done, and the big time thump. They're overwhelmed, and lose their equilibrium.

Not so much an issue of literally knocking down so much as potential to put down and out.

 

[JShirley]

Right! Exactly. Only so many ways to reliably stop a machine. They are:

1) Electrical failure
2) Hydraulic failure
3) Structural failure

 

[Dave R]

Just to disagree a little...

Some first hand experience. I lined up two rows of plastic gallon milk jugs, filled with water. 5 in each row. Shot the first row with .308 milsurp from 25 yards. Thought I missed. Then I saw the leaking and found a .30 hole through each jug. Don't know how much the bullet slowed, but it didn't dump much energy.

Then I shot the 2nd row with a .308 150gr Remington Core Lokt. Big explosion! Water everywhere! First jug nearly reduced to a single sheet of plastic. 2nd jug similar. Major rip in 3rd jug. Big hole in 4th jug. Bullet yawed and exited 4th jug.

There was certainly a BIG difference in the "knock down power" of those two rounds. Or energy dump, or terminal ballistics, or whatever you want to call it.

Anybody know the formula for Taylor Knock-Down? Something to do with caliber, bullet weight and velocity, with heavy weighting on weight and caliber. Don't know if I believe in that one.

Big and slow, or small and fast, there is a definite difference in how much energy some rounds transfer to the target.

 

[only1asterisk]

Knocking a person down is not stopping them!

It is fully possible for a small arms projectile to knock down a person. There is a set of circumstances that have to coincide, but it is possible.

1. The projectile must have significant momentum.
2. The momentum must be transferred efficiently to the target.
3. The impact must be near a balance point.
4. It helps if the person is off balance or moving (reducing the impact required).

Imagine a SWAT type being stuck from behind in the shoulder by a 12 gauge slug while bent forward. His vest stops the slug, but the impact knocks him over. Not picked up, off his feet and thrown across the room like in the movies, but knocked off his feet as surely as if I pushed him.
There is a huge difference between getting hit it the hip when you are not expecting it and taking the recoil of a gun of your shoulder when you are. The martial artist here should be able to confirm how little force it takes to knock a person down.

I would be willing to bet the impact of a 338 Lapua on a trauma plate is enough to knock most people down, even though it doesn’t strike a balance point (provided they are not braced for the impact the trauma plate stops the bullet). I have yet to find any volunteers to help me with this experiment!

By the way, there are rifles that recoil enough to put the unwary shooter on his/her ???. Witness the video at the link marked Ignorance in my signature.


David

 

[russlate]

I think there is such a thing as shock.

I don't know how to quantify it.

I'm 5'4" with size 8 hands and feet. I practiced long and hard shooting hi power loads for handguns - full charge 357, 41, and 44 magnums. I eventually managed to maintain expert proficiency on various courses of fire with the 41, although it tore the web of my hand up.

At the same time I was shooting 90, 91, 92 with the 41, I was shooting 97, 98 on the same course with full charge 357 125 gr loads in a 2 1/2 snubby.

But with essentially the same gun only in 44 mag, I could not maintain a course of fire. I'd let off a shot and the concussion and smack to my hand wiped out my intension of continuing to fire and I was standing there dazed for a few seconds.

Something knocked me for a loop. What I don't know, but if it works on one end of the gun it must operate on the other. See the Taylor Knock Out Values for big game.

Beats me. But the same thing happened with my 458 as with the 44 mag. Give me a 7x57 or 25-06 and I'll dot "i"'s with them.

End of ramble. If you want it to make sense you'll understand what I'm saying. If you don't want to hear you won't, and nobody can make you see while you keep your eyes closed.

 

[telewinz]

Knock down power seems to me to be very mis-understood. Reading from the old authors such as Hatcher and Keith, it really means incapacity power ( and was often explained as such) with the ideal round putting an enraged BG down with one hit to the torso. I have never read any author state that their was enough energy in any handgun caliber to "force" a BG down, to the contrary it was alway related to the nervous system.

 

[mete]

For handguns there is no such thing as "knock down power" However there is stopping power and this is what we look for . RUSSLATE there is shock and it is to the nervous system and this is a major part of stopping power. This is also why people who are high on drugs or even adrenelin seem to be immune to the normal stopping power. The drugs have a major effect on the nervous system, I remember an incident where a cop hit the BG 6 times with full 41mag loads - the only reason the BG stopped was that his leg was broken and he survived even tho he lost 7 pints of blood.

 

[Ron L]

I'll jump on the same bandwagon as redneck.

Now I realize it's been quite a while since I've been in school, but I don't think the laws of physics have changed much since that time. "For every action, there is an equal and opposite reaction." Now, something powerful enough to knock down a 175 pound BG would certainly have a similar effect on my 175 lbs (me+gun combined). I realize that how you're standing and balance and all that plays a part, but if something is strong enough to lift and throw a BG a'la Hollywood, I'd probably be in a world of hurt as well. YMMV.

Part of this has to do with semantics - "knock-down" power versus "stopping" power. Another part has to do with myth versus reality.

 

[Art Eatman]

Jackrabbit broadside to me. 1911 with max load and Hornady 230-grain flatnose. Center-punched the rib cage.

Rabbit sorta humped up in the middle and looked very insulted. After a goodly number of seconds, hopped off a few steps and fell over. So, what "knockdown"?

It's best to shoot for the neck and let gravity work. That's a failsafe combination.

Art

 

[RustyHammer]

Definition of knock down power ... see these clips!

http://www.dogbegone.com/video.htm

 

[Dave Markowitz]

If you want knockdown power, use a Buick.

 

[BigG]

Buick - 456,934 foot pounds of knockdown power! Read about it in next month's issue!

 

[Midiman]

Are you using a 55gr .223 FMJ that enters the target at 3000 FPS, and exits the other side at 2700 FPS

55gr .223 will rarely ever cause an exit wound. It hits its target and immediately starts tumbling and fragmenting causing a nasty, gooey mess.

 

[JShirley]

Welcome to THR. Good to have you.

Actually, that depends on the length of the shooter's barrel, the distance to the target, and the thickness of the target.

John

 

[Sunray]

russlate, everything you describe is related to recoil. I'd bet that that .44 did not fit your hand worth beans. I'd also bet that .458, that beats on everybody, was not a very heavy rifle. (guy came in the store I was in, ordered a .458 and a box of 20 rounds. Picked it up Friday night, came back Sat afternoon with the rifle and 18 rounds asking us to sell it. The .458 is a short extremely heavy recoiling cartridge. Other .45 cal rifles like the .45-70 are not as big a deal due to the way their powder burns. Mind you, 70 grains of BP out of a trapdoor carbine hurts)
Try a .458 in a 15 or 20 pound rifle and see the difference. Try a revolver that fits your hand(think Super Redhawk. Same grip as a GP100) and see the difference.
As to "knock down power" No there is no such thing. Except in Hollywood. When a body gets hit, the shock causes the body to immediately stop working properly. The brain may not register this though. If this shock is big enough, the brain hears about it and shuts off. Said body drops straight down, if standing. Momentum can cause the body to keep going briefly but not for long. This is why we hear of soldiers losing large body parts and not dropping.
There is no pistol round that will take the fight out of a bad guy reliably 100% of the time with one shot. Read Ron L's response. Aint science grand?

 

[Midiman]

Actually, that depends on the length of the shooter's barrel, the distance to the target, and the thickness of the target.

Some of these factors may play a very small role but I can assure you the thickness of the target does not. I frequently use a piece of relective foam core slanted behind my target stand to aid in seeing .223 holes in the black with my spotting scope. The holes go perfectly round through the paper target and 1 to 1.5' further back, when they hit the foam core, perfect keyhole! It doesn't take much of anything to start the tumbling.

 

[Mannlicher]

There are so many folks posting here that are evidently much smarter than I am.

However, no matter what you call it, (or dont' call it), some cartridge/loads make things fall down quicker than others, and on a fairly consistant basis.
's a fact, and readily observable.

There may be a problem with semantics, but there should be no problem with understanding that the terminal effect of a .45 ACP is greater than that of a .25 ACP.

 

[redneck2]

Might as well jump on the pile...

there was an article some time back about this subject

writer took a sandbag and set it on some wooden "legs" to simulate a deer and shot it with everything up to a .458

nothing knocked it over...it'd be easy to duplicate if one cared to

still.....I've seen .58 cal Minie balls hit a dirt bank. Big "thud" and lots 'o dirt in the air. I can't see how anyone hit with one of those things could stand up afterwards.

 

[Moparmike]

Well, I can think of one or two guns that would have some knockdown power.

1. Anything that shoots pumpkins. I am sorry, but if it can launch a pumpkin 2000 yards it can sure as heck knock me down.
2. My potato gun. Launches a potato the size of a beer can 110 yards with a little help from Gunk Bug & Tar Remover and a flame.

Honestly, I didnt know that KDP was a hoax. The things you learn.

 

[Dr.Rob]

Well I have shot a mule deer with a 54 cal bullet wieghing in at 400 grains and powered by 100 grains of pyrodex. The deer happily bounded away.

I tracked that deer for 2 hours, through heavy brush, open woods, and finally through a creek.

The animal had been hit in one lung, the liver and bruised in the heart, the slug exited the body and the initial blood trail looked like a Friday the 13th movie set.

I've had a 180 grain 30-06 bronze point bullet at 2700 fps FAIL (meaning the bullet disintrgrated on impact, leaving a cratering wound that DID NOT penetrate into the vitals (NO bullet/fragment/bonesplinters at all in the body cavity) Result= DRT. Dead right there, in its tracks the biggest uncommon antelope doe I ever shot.

I've also seen a 7mm mag centerpunch an antelope through the body, hitting NOTHING but the diaphram. The animal (as we discovered later when my partner finally got the killing shot to the head) probably would have survived the wound.

The lesson?

Animals are reactive targets. The do not respond to bullets the way clay, ballistic gel, or paper targets do.

Knock down power may indeed be a myth, but I still wouldn't hunt deer with a 223.

 

[itgoesboom]

I think some people are confusing "stopping" power with "knockdown" power.

Think of it this way.

A .45 hit COM has a better chance of "stopping" a threat than a .25 in the same spot.

Neither will throw the bad guy up against the wall, arms and legs flailing.

"Knockdown" power is when there is enough energy to pick the target up and off its feet purely by force (rather than the target thinking "OH **** I've been shot, i better fall down.").

It's been said before, and i think it needs to be said again: for every action, there is an EQUAL and OPPOSITE reaction.

JShirly had it right....3 ways of stopping any machine

1. Electrical outage (hit the central nervous system, the perp will drop cuz he's turned off.)

2. Hydralic outage (the BG bleeds out, and then falls down due to lack of blood, and his system shuts down.)

3. Stuctural damage (you hit the BG in the kneecap, it shatters, he no longer can support his body on that leg, becomes unbalanced and falls over).

In none of those cases would the BG be lifted off his feet and thrown against the wall. Ofcourse, since we are talking humans here, there is always the effect of "OHH **** i have been shot, i am going to die..." and a person dropping to the ground because of that.

"Knockdown Power" does exist....in crew served weapons.

I.G.B.