If you can get within 200 yards, you should be fine with a 62 grain (SS109) should be fine, given a good target presentation.
I prefer a heavier round for game hunting. The reason that I would trust an AR against a human everytime,but not a 4 legged critter is that you cannot always be sure of the angle you are going to get. With a human, you won't have to penetrate more that a few inches to get to something vital. A shot from the rear or throught the shoulder could require 10-12 inches of travel through the body to reach heart/lungs. A .223 bullet may not live up to that challenge.
If it were going to hunt with the AR, I'd buy some Winchester CXP1 (2 if it is available) Ballistic Silver tip .223. I've seen what the BST ammo will do on aninals in a few larger calibers at a few different angles and it is very effective.