Ok I got to thinking about why a .223 isn' t considerd enough gun for whitetail deer and did a few calculations on bullet energy and big game animals. What I came up with is pretty interesting. Looking at these numbers why do we need so much bullet weight and energy to kill a whitetail deer? The 223 produces more weight per pound and energy per pound than any of the other cartriges. This is assuming that you use a properly constructed bullet in the 223. What makes a cape buffalo so much easier to kill than a whitetail.

This is how I got these figures:
weight of bullet divided by weight of animal = grains per pound of animal

grain per pound of animal (velocity squared)
_____________________________________ = foot pounds per pound of animal
450400



2000# cape buffalo, 416 Rigby, 400 gr bullet @ 2400 fps. = .2 gr of bullet per pound of animal and 2.56 ftlbs per pound of animal

1200# moose, 338 win mag, 225 gr bullet @ 2750 fps. = .188 gr of bullet per pound of animal and 3.15 ftlbs per pound of animal

600# elk, 300 win mag, 180 gr bullet @ 2900 fps.= .277 gr of bullet per pound of animal and 5.17 ftlbs per pound of animal

150# whitetail. 270 win, 130 gr bullet @ 3000 fps. = .867 gr of bullet per pound of animal and 17.32 ftlbs per pound of animal

150# whitetail, 223 rem, 70 gr bullet @ 2900 fps. = .467 gr of bullet per pound of animal and 8.71 ftlbs per pound of animal.