Help with an Argument on "knock down" power

Have you clarified what exactly he means by the term knock down power? Even though we agree that its a myth, people uses the phrase in different ways.

For example I frequently hear fellow hunter say things like, " .308 has better knock down power than .223", etc. What they mean is that .308 incapacitates the deer quicker than .223, not that it literally knocks the deer off its feet.

I would be inclined to think that your friend is trying to say that 45acp is more effective at incapacitating bad guys than 9mm, 380, etc. If this is the case, challenge him to appeal to any credible statistics that prove his case. That said, I have met people naive enough to think that shotguns can send people crashing backwards through walls like in the movies...:rolleyes:
 
He means that a bullet can knock over by it's energy an assailant and that it would not knock over the shooter as Newton's Third law implies. This is because the mass of the handgun would absorb the recoil (to about 99%).
 
He means that a bullet can knock over by it's energy an assailant and that it would not knock over the shooter as Newton's Third law implies. This is because the mass of the handgun would absorb the recoil (to about 99%).
Click to expand...

There is no convincing some people even when its obvious they are talking absolute rubbish. If they are that stupid you have to ask yourself is it worth trying.
 
Tilting at windmills

Your friend has his mind made up. don't confuse him with facts!

My good friend Joe is of the same opinion as your friend. Uh Joe when I shoot that chunk of firewood over there, will I knock it over. Joe: Well of course it will knock it down. Uh no it will not. Unless it is a very light piece of firewood it will barely move, if at all. Joe there is no such thing as knock down power.

Could not shoot there to demonstrate. I'll have to take Joe out to the woods sometime and demonstrate. He has only shot holes in paper.
Ohh and seen too many movies.

The folks that hold these beliefs can be in very deep Kim-Chee if they ever have to defend themselves. They are expecting one shot from a PPK (Joe's gun) to knock over the bad guy.
 
Tennessee Gentleman said:
So any physics folks here? This is his reply as to the application of Newton's Law.

"Enough with the Newton’s Law crap! When used as an argument it sounds good, and apparently is very popular, but it does NOT work as you suggest. As I said before, that is simply throwing out a fine sounding physics term, but not doing the calculation! Except when the weight of the firearm is equal to the weight of the projectile, the weapon design includes no springs, slides, ejection mechanism or any other force mitigating features, then it does apply as you suggest.
Click to expand...
Most of his variables can be eliminated by using a Colt SAA revolver instead of a 1911 -- and that has a more powerful cartridge, so that mitigates the recoil absorption of the firearm itself.

That said, the essence of science is to prove the theory through experimentation. Several people have already suggested that he put his assertion to the test -- buy a bag of mason's sand from Lowe's or Home Depot for five bucks, balance it in a vertical orientation, then shoot it from 15 or 25 feet away and see how far it moves.

Several years ago I was at competition night at the range where I shoot. That night the competition included a plate rack. I was shooting a 1911 in .45 Auto, using standard power FMJ ammo (most likely Winchester white box). When my turn came, I started blasting away -- and nothing happened. The RSO confirmed that every shot hit a plate, but the plates didn't fall. I don't know how much the plates weighed -- they were 1-inch thick, so if they were 8 inches in diameter they would have weighed just about 15 pounds. They had to adjust the setting on the rack so the plates would almost fall over by themselves.

Not long after, the range bought a new set of plates, made of hardened alloy to withstand bullet impact, that were only 1/2-inch thick. Those work much better.

My point being that if a standard power .45 bullet won't knock over a 15-pound steel plate, it certainly won't knock over a 200-pound human being.
 
Have you ever gone hunting? Shoot a deer with a 30-06 and it will likely crouch and run then fall over nearly dead. Shot several that fell right there but were kill shots to the neck and the deer was not knocked down.
 
I love 1911 mythology. In separate conversations, two big guys (over 6' 2") told me that they once fired a 1911 and it 'damned near tore their arms off'.

Little ol' 5 6" me said, well, look at my hand, I fired about 100 230 gr. rounds this weekend, and I'm still seeing my hand. Oops.

The videos are convincing as is the math! Thanks for the analyses.
 
You're right. And your friend is dead wrong about the force exerted by the bullet on the shooter. As soon as the "pressure vessel" is broken (the bullet leaves the barrel), the bullet no longer exerts any force on the shooter.

Interesting story: back in the old days when bullet tech was in it's infancy, the govt chose bullets/loads/firearms by shooting hanging corpses. Whichever load swung the corpses farthest, that was their choice. Was a flawed way of thinking then, and is a flawed way of thinking now haha.
 
Cheapshooter said:
The youtube of the episode has been blocked by the network, but Mythbusters did this very experiment. They couldn't even knock down a man sized dummy with a 50 BMG!
Click to expand...
The physics is straight forward and simple, but you have to identify and solve for the not-so-obvious issue:
While Mythbusters may not have been able to knock over a man sized dummy with a .50 BMG, the issue is the energy absorbed by the target. If half the 12K ft lbs of energy had been absorbed by the 200 pound dummy, 6000 ft-lbs/200 lbs = moving the dummy 30 feet.
Clearly the dummy in the Mythbusters experiment didn't absorb much of the energy.
Take an extreme example: What happens when a 660 grain / 12,000 ft lb .50 BMG round hits a 20 gram / 300 grain target. If most of the energy was absorbed by the paper, the paper should travel a very long distance (miles without wind resistance). But it doesn't because it takes very little energy (a few ft lbs) to poke a hole in a piece of paper.

So the trick to "knockdown power" is the target absorbing the kinetic energy. In an ideal world, a "bullet trap absorbs all the kinetic energy of a bullet.

If a bullet passes through a body, much of the 'knockdown power' is lost.
 
Without going into every calculation [I’ve showed enough work here—BTW, I did not just look this up somewhere, I calculated it then used online tools to check my work], for a .45 that weighs 2.5 pounds (an empty standard 1911 is 2.4 so I rounded), the backward force (recoil) is 8 ft-lbs. (Which is less that dropping a 1 lb weight from 3.5 m)
Click to expand...

Not going to check your math, nor argue with your application of formulae, but consider this, the calculated muzzle energy of a .45 round is around 360ish ft/lbs. Equivalent to dropping a 360lb weight ONE foot.

Science is only science if it is applied. “Science” doesn’t tell us anything. Newton does not support the argument, when actually applied."
Click to expand...

This is the key, call it science or math, it must be applied correctly to the situation, and even then can be correctly applied and still not explain observed results.]

Math can "prove" or disprove almost anything, depending on how it is applied. Math (according to the old story) tells us that a bumblebee cannot fly. Yet, the bee, not knowing math, flies just fine.

A saw a physics problem once, a swimmer at a pool, starts on the edge, dives in, swims to the other end, then back, and gets out right where he started. Math "proves" he went nowhere. (the exercise was to use the math and show he went nowhere) And, under math rules, it did prove he went nowhere.

Trouble is, in the real world, he did go somewhere. We saw him swim the length of the pool, and then back. distance was traveled. We observed it. But, math, applied in a certain way, says he went nowhere, since he ended up right where he started.

This is the thing about "knockdown power". It is real, it is an observed effect. You cannot deny the effect exists, people have seen it, many, many times.

However, there is, to date, no theory or formula that explains it, and none that reliably predicts it. Many have theories and ratings that appear to be correct in some situations, but do not accurately fit observed results in ALL situations. Some use energy as their main factor, some use momentum, some include bullet shape, NONE have proven accurate across the entire range of situations.

I believe none can. I believe the observed "knock down" effect is something
that happens only when shooting living animals (including people). Shooting something else does not, and cannot replicate the effect.

I believe the effect is created not by the energy or momentum, or shape of the bullet in any quantifiable way. I think it is the reaction of the body's nervous system "short circuiting" in some way, as a result of the bullet strike. it is the muscles of the animal, driven by these nerve impulses that "knock" it off its feet, when that does happen.

Because it doesn't always happen. And when it does happen, it happens in random direction and strength. Every different bullet strike contains a host of different factors, which are simply not quantifiable and so cannot be accurately used in any equation. The biggest of these is simply that every individual animal or person shot is a different individual.

There is a bell curve of results, and while the majority will be in the middle of the curve and therefore show similar results, there are situations on each end of the curve where the results are vastly different.

One guy might be "blown off his feet" by a hit from "X" and another hit with the same thing, in the same place might just stand there, or even be "blown" forward, rather than backwards. I believe the difference is due to how the target's nervous system reacted to the shot, or didn't, not because of the calculated anything about the bullet itself.

In other words, one guy might get spun around from a hit in the hand with a .45acp (and probably did, somewhere, sometime, and so the legend is born) while the next guy, shot in the hand might just look at the hole in his hand, and think, "hmm, damn, I've been shot..."

My personal theory is in my signature line, and note that its not stated in absolutes, and is based on my lifetime of observed results.
 
He is a .45 ACP guy.

So, what am I missing?
Click to expand...

The chance to just smile and let him believe what he wants to believe. Its an argument you most likely won't win. You have to choose your battles.
 
With about 2% of the population, they have an exaggeration response to injury and basically faint when they see or feel a penetrative wound, see blood, or think they were injured, etc.

That might explain some of the folks who get a minor hit and keel over.
 
TG said:
So any physics folks here?
Click to expand...

I'm not a physicist, but I drive by a Holiday Inn each evening.

I went to school with a fellow who was a boxer in the Army. He was my size but in better shape and his hands were so fast I couldn't follow his fists with my eye. Had he punched me in the face or my solar plexus, he'd have certainly knocked me down, but not because his punch had the force to take a couple of hundred pounds and move it a few feet. And, of course, his own punch didn't knock him down either.

It seems reasonable that a handgun round with good power delivering a bullet to the right spot could put someone down just like a well delivered punch, but that isn't the same sort of knock down as one football player running into another so as to knock a player off his feet.
 
Guys, what part of this actual demonstration (@1:00) is unclear ?
https://www.youtube.com/watch?v=BgZPusyLeMA

Sooner or later you have to quit playing with cocktail circuit theory, and just go out and do it.




and if you don't like that, then play the romp`em stomp`em 12 gauge slug (2,500ft-lb) doing 1,600 game. (@3:00 same video)


.
 
Last edited:
44 AMP said:
but consider this, the calculated muzzle energy of a .45 round is around 360ish ft/lbs. Equivalent to dropping a 360lb weight ONE foot.
Click to expand...

Actually according to thishttp://gunownersofcanada.ca/showthread.php?37173-THE-FBI-PAPER-HANDGUN-WOUNDING-FACTORS-AND-EFFECTIVENESS

"Goddard amply proves the fallacy of "knock-down power" by calculating the heights (and resultant velocities) from which a one pound weight and a ten pound weight must be dropped to equal the momentum of 9mm and .45ACP projectiles at muzzle velocities, respectively. The results are revealing. In order to equal the impact of a 9mm bullet at its muzzle velocity, a one pound weight must be dropped from a height of 5.96 feet, achieving a velocity of 19.6 fps. To equal the impact of a .45ACP bullet, the one pound weight needs a velocity of 27.1 fps and must be dropped from a height of 11.4 feet. A ten pound weight equals the impact of a 9mm bullet when dropped from a height of 0.72 inches (velocity attained is 1.96 fps), and equals the impact of a .45 when dropped from 1.37 inches (achieving a velocity of 2.71 fps)"

Goddard, Stanley: "Some Issues for Consideration in Choosing Between 9mm and .45ACP Handguns", Battelle Labs, Ballistic Sciences, Ordnance Systems and Technology Section, Columbus, OH, presented to the FBI Academy, 2/16/88, pages 3-4.
 
Clearly the dummy in the Mythbusters experiment didn't absorb much of the energy.
Click to expand...
The dummy was rigged with an armor plate in the torso. The bullet did not pass through the dummy in the test--it was stopped in the torso.

The dummy was dislodged from its supports but it fell more or less straight down after that.
 
First we need to properly definite "knock down". Without a definition, we just get hand wavings of different kinds.

Physics is study of energy transfer. A rifle bullet has kinetic energy of 1000 ft-lb. That energy can lift a 1000lb straight up by 1 foot. That is a lot of energy. The only question is how to transfer that energy to the object that we want to move.

Newton's 3rd law is surely valid. But it needs to be applied correctly, or it is just used to wave more hands. Say I stand a few feet from you. I have a sludge hammer is my hands. I swing that hammer and hit it square on your chest. You will be on the ground a few feet back, and I will be standing. Newton's 3rd doesn't work, does it?

-TL

Sent from my SM-G930T using Tapatalk
 
You must log in or register to reply here.
Back
Top