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# "Knock down" power

#8
12-01-2001, 04:18 PM
 Bronze Member Join Date: Nov 2001 Location: Sydney Australia Posts: 40
Re: "Knock down" power

If a bullet has 3000 ft/lbs of kinetic energy, than that is sufficient energy to lift a 3000 pound weight by a height of 1 foot or a 1 pound weight by a height of 3000 feet or a 200 pound weight by 15 feet etc.

Energy is "work" and power is the rate at which work is done.

So the bottom line is that the bullet does have enough energy to lift the deer 15 feet. However the energy is not released in the right way for this to happen.

It is kind of like "gearing".

If we could somehow attach a very (very very [img]images/icons/grin.gif[/img]) long string to the bullet and that string was wound around a pulley or drum and then the pulley was geared way down, then the final pulley at the end of the gearing could be used to wind up a 200 pound deer.

If the gearing was right and there were no losses from friction, then the deer would be lifted 15 feet before the bullet stopped.

If we now let the deer fall back down and the gearing system was still in place, then when the deer hit the ground, the bullet would have of course been wound back by the string and "presto" it would be back at its muzzle velocity and the deer would be at rest

Mike
#9
12-01-2001, 06:17 PM
 Silver Member Join Date: May 2001 Location: wis Posts: 104
Re: "Knock down" power

I just wish that I could have some of those magic bullets that blow cars up with a 9mm pistol or totaly flip cars into the air with a rifle. Besides that game does fall and flip around a lot when you brain them or spine them. I spined nice 8 pt with my bow at 15 yards last year. looked like I just fliped him off his feet. But a arrow only has a little bit of the foot lps that a rilfe has . Knocking them down has a lot more to do with where you hit them and what the critter is doing at the time. You brain and or spine a running critter your going to see some real action like you blew them off their feet. But it is just the motion of their body causeing it. A head shot rabbit jumbs all over the place and it sure isn't from the bullet.
#10
12-11-2001, 10:06 AM
 Junior Member Join Date: Dec 2001 Location: Kentucky Posts: 9
Re: "Knock down" power

I agree that a knockdown on big game is most likely some kind of shock to the CNS that causes them to be unable to stand, either for a moment, or for good. I have never witnessed such a hit.
#11
12-11-2001, 11:22 AM
 Silver Member Join Date: Dec 2001 Location: Canyon Ferry, MT Posts: 324
Re: "Knock down" power

OK, I'll add my 2 cents here.

First, I agree that no bullet will knock an animal down like a wrecking ball would.

The way see it animals go down for the following reasons:

1. Overwhelming shock to or severing of the central nervous system.

2. Oxygen starvation to brain or muscles from bleeding or non-circulation.

3. Destruction of critical support skeletal structure.

Any hit that causes one or more of these to happen will drop the animal, regardless of velocity, energy, or caliber.

Any hit that fails to cause one of these to happen will fail to drop the animal, regardless of velocity energy, or caliber.

A marksman who understands these three principles and the capabilities/limitations of his equipment is the most critical part of succesful kills. Good shooting! MM
#12
12-27-2001, 11:11 AM
 Platinum Member Join Date: Dec 2001 Location: Long Island, New York Posts: 2,517
Re: "Knock down" power

The only animal that I've seen "knocked off his feet" by a projectile was all those big black & white critters that when down when the frat boys got all liquored up and went out cow-tippin' [img]images/icons/smile.gif[/img] [img]images/icons/smile.gif[/img] [img]images/icons/smile.gif[/img] [img]images/icons/smile.gif[/img] [img]images/icons/smile.gif[/img] [img]images/icons/smile.gif[/img] [img]images/icons/smile.gif[/img]
VH
#13
12-28-2001, 05:15 PM
 Platinum Member Join Date: Dec 2001 Location: Mukilteo, WA Posts: 1,092
Re: "Knock down" power

Dave, your conclusions are correct but your math is wrong [img]images/icons/wink.gif[/img] Let's see if I can help. [img]images/icons/smile.gif[/img]

Energy isn't what we're concerned about, it's conservation of momentum (mass*velocity, not 1/2mv^2).

The mass of the bullet times it's velocity will be equal to the mass of the deer+bullet times their velocity after the hit (assuming they stick together).

For example, say you hit a 150 lb deer with a 180 traveling at 3000 fps. The velocity of you impart on the deer will be 180*3000/(150*7000+180)=0.514 fps. Pushing a deer sideways with your pinky at 1/2 a fps is hardly going to knock it down.

The same goes for the recoil you absorb, except in this case you'll absorb more than the bullet will expend on the target because the mass and velocity of the powder is working against you but won't make it to the target.

Make sense?

I too get a chuckle when I see somebody get knocked accross the room, up into the air and out the window, etc after being shot in a movie.

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