Anything up to a deer. It can still be used on a deer but lots of things become more critical, and the skill level like Art said is the big one. Thats just my thoughts, but I think this subject been beaten to death.
my bro hunts deer with his 223 and does OK with it, but I like to use the 7.62x54R. I just like to know it is going to punch a big old hole through them.