I've shot lots of prairie dogs with it, makes a nice whack...

But not CoM on a small animal....a M-16 shoots a .22 caliber projectile.. Not faster than a 22 just heavier and pointed... .22 on a human..., eye socket, nasal cavity & sinuses, oral cavity, ear canal, rear base of skull, pretty much anywhere but an angled blow to a cro-magnon forehead and they are on the ground...and even a blow that doesn't penetrate the skull will put you down making you wish that you only had a migraine... Soft meat not so much...