I've been playing with some numbers this afternoon, and I'll throw this idea out there just for discussion.... It is similar to the long standing idea of having a minimum of 1 FPE of energy per pound of body weight of the target.... I am a firm believer in the relationship between momentum and killing power.... While things like the Meplat diameter affect the diameter of the wound channel, and the sectional density (or the sectional density but using the meplat diameter instead of the caliber) affects the penetration.... you still have to hit an animal hard enough to kill it.... and the bigger it is, the harder you have to hit it....
The momentum of a bullet at impact is the weight in lbs. times the velocity in fps.... That works out to the weight in grains divided by (7000 times 32.4) times the velocity in fps.... ie W (gr.) x V (fps) / 226,800.... The resulting number would be about 0.8 for a 200 gr. bullet travelling at 900 fps.... pretty hard to relate to the weight of an animal.... If instead of dividing by 226,800 we divide by 1000, the number is now 180.... hmmmmmmmmm.... would a 200 gr. bullet travelling at 900 fps (at impact) drop a 180 lb. animal?.... I would think that would be pretty close....
Here are some other examples....
8 gr. @ 450 fps = 3.6 lbs (low powered .177)
8 gr. @ 900 fps = 7.2 lbs (high powered .177)
16 gr. @ 900 fps = 14.4 lbs (high powered .22)
30 gr. @ 900 fps = 27 lbs (high powered .25)
40 gr. @ 1200 fps = 48 lbs (eg. .22 LR rimfire)
78 gr. @ 900 fps= 70 lbs (low powered 9mm)
158 gr. @ 900 fps = 142 lbs (high powered 9mm)
230 gr. @ 900 fps = 207 lbs (low powered .45 cal)
170 gr. @ 2000 = 340 lbs (eg. 30/30 Winchester)
450 gr. @ 900 fps = 405 lbs (high powered .45 cal)
220 gr. @ 2500 = 550 lbs (eg. 30-06 Springfield)
570 gr. @ 2000 = 1140 lbs (eg. .500 Nitro Express)
I think those numbers are fairly realistic, maybe a bit on the low side.... Want to make it even simpler?.... How about if you have an air rifle that shoots in the high subsonic (say 900-950 fps) you just use the bullet weight in grains for the animal weight in pounds....
8 gr. pellet - 8 lbs.
16 gr. pellet - 16 lbs.
30 gr. pellet - 30 lbs.
100 gr. bullet - 100 lbs.
200 gr. bullet - 200 lbs.
400 gr. bullet - 400 lbs.
Since we have pretty much found out over the years that we don't want to push velocities over about 1000 fps (but we want to get close).... could you ask for a simpler guide to killing power?.... Incidently, at 950 fps, the energy is 2 FPE per gr. of pellet weight.... so we have values about twice the bare minimum FPE if you go by the above numbers....
Bob
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