Is "knockdown power" real?

[freedom]

while in theory this is true in this particular instance the force on the shooter is actually GREATER. when a round is fired in the gun it is pushing with ALL of its force backwards as its actually being held in place, when it hits, most of that force is used to penetrate so actually in most instances you'd have a greater chance of being knocked down from SHOOTING a big gun than being hit by one

Some though is being used to work the action and overcome the weight of the firearm itself. It's also being spread out over a greater area, a grip and two hands or a shoulder.

 

[Bushwhacker]

Pretty cool little back yard experiment. No 45-70?? 500grains is a lot of mass moving faster... . Relative to the size of the target the .380 and the .450 size projectiles are very similar in mass and not too far off in weight so in that situation I would expect a similar outcome. Using your hand with less force but more mass would have a more noticeable impact I would think. Your hand will cover more area than a .38" projectile so more energy will be transferred across a broader area...

A train moving 1mph will knock you down, run over you and kill you, because of mass. Same train moving 60mph will disintegrate you because of mass and velocity. I'll take a train half the size moving 60mph over the train moving 1mph that is heavier.

Speed kills.

 

[Tony2X]

I keep hearing about how certain bullets have more "knockdown power" than others.
Some say it comes from big, heavy bullets. 200 grain 10mm or .45's or even .44 magnums.
Some say "knockdown power" comes from kinetic energy, which is based on mass x velocity x velocity again (velocity is squared, so it counts MUCH MORE than bullet weight).

Here's my little experiment:


I took some 7" to 8" diameter pine logs, freshly cut from pine trees I just felled.
I cut a few of these logs into 5 foot lengths and stood them on their ends on a concrete slab.
Any log that didn't have a nice clean and square cut on the end, or for some other reason didn't balance well, was rejected.

Then I shot these logs with a variety of guns. 22LR, .38 spl, 9mm, .40, and .45. I used various bullet weights, including 9mm 124 gr. +P, and 230 grain Gold Dot HP from the .45.
I shot the logs with 12 and 20 gauge shotguns at point-blank range (10 feet), using small birdshot, then buckshot (#2 for the 20 ga; but 00 buck for the 12-bore). And I shot the logs with slugs.

Nothing exited any log. Every bullet or slug or pellet was FULLY contained by the log, and all hits were near the center of the log as it faced me. No bullets glanced off or ricocheted, potentially spending their energy on some secondary target. All kinetic energy was absorbed by the logs, each free-standing and balanced on its 7" or 8" diameter base.

RESULT: No handgun bullets even made any log sway or wobble. The logs just stood there and absorbed all the hits without moving.

The 20 gauge shotgun made the logs sway a little, but it didn't make any log fall over.

The 12 gauge shotgun with slugs and buckshot pushed the logs enough that one time, one of them fell over, but the rest did not, and the one log that fell actually rocked back and then recovered and rocked forward, and ultimately fell to the ground FORWARD, toward me. That log, hit with a 12 gauge slug, was the only one to fall down.


No logs were knocked over backward.

All of these logs were easily pushed over by hand, with just a slap of an open palm, or a quick jab punch, done without drawing your fist back very far. These logs could also be knocked over by throwing bricks or grapefruit-sized rocks at them.

BOTTOM LINE: Don't count on "kinetic energy" numbers to translate to literal man-shoving abilities, when it comes to bullets. A handgun cartridge that generates "400 foot-pounds" of energy will NOT lift a 400 lb. man off his feet, not even an inch, nor a 200 lb. man. Not even a 50-lb coyote. Maybe a 10-lb groundhog. Maybe.

Shoulda used an AK.

 

[Allsmiles]

As a deer hunter, I have shot deer that have ran/fell, stumbled/fell, or fell flat when shot. All with the exact same round (Wolf 7.62x39 123 HP). The where is just as important as to the what is being used.

 

[CBH13]

Some though is being used to work the action and overcome the weight of the firearm itself. It's also being spread out over a greater area, a grip and two hands or a shoulder.

action would indeed also absorb some of it but that matters on the firearm and honestly I had a revolver in mind when trying to explain it. and the force from the firearm may be spread out further but it is still all force being blunt pushed backwards as there is no "give" where as when the round strikes a lot of the force it displaced out (more so in hollow points) and then whatever force is still behind the round just pushes it through instead of directly transferring the energy.

 

[JimJohn]

357sig because goobers like Tex Grebner shot himself in the thigh with a 45 and walked away

 

[Hayata]

I think knock down power is a Hollywoodism.

 

[Tazz]

Every action has an equal and opposite reaction. The force acting one the one getting shot is roughly equal to the force acting upon the shooter.

Equal and opposite reaction, Basic physics. If it didn't knock you down shooting it, it won't "knock down" a target of comparable size and weight.

Yall beat me too it. I saw a video years ago in the VHS days before DVD's, can't remember the name of it but it was made by some guy who was manufacturing body armor. The video was about penetrating power, but what I remember most was the guy let one of his employees shoot him several times while wearing soft armor with a .44 magnum, he even stood on one leg and never got knocked down. Then he wore one of his rifle vests and also stood on one leg while the other guy shot him with a .308 FN FAL, still no knock down. All these shots were from about 5 feet or less. This was back in the late 80's if I remember right, it was a real eye opener for me. The only way you're gonna knock anybody down with a gun is to whop em' upside the head with it. Total disruption of the central nervous system will drop a mofo in his tracks but it still ain't gonna knock his ass down. Simple physics man, simple physics and I didn't even study physics in school 40 freakin' years ago. Lol!

ETA: One really cool part of the video showed them shooting a .50 BMG round through an old Buick, 2 pieces of 1/4" plate steel mounted on either side of that big ass 455 and that .50 BMG rd cut right through the car, both sheets of plate steel AND the engine block. That was pretty badass to see those results.

 

[Radar363]

I'm certainly no physicist but comparing projectiles to your hand or a train is apples to oranges: the projectile has a finite amount of energy behind it where your hand has a continuous amount of energy as long as you keep pushing. There is no 'energy dump' when you are pushing. Punching or striking, maybe..

 

[tstover]

Equal and opposite reaction, Basic physics. If it didn't knock you down shooting it, it won't "knock down" a target of comparable size and weight.

I've tried explaining that to people a few times and they say - but but but.... it... it...
Then i shake my head.