I'd say a 223 or 22-250. Whatever you choose DO NOT[:'(] use a polymere tipped bullet like a V-Max. They have a nasty tendency to blow up on contact at high speeds(like 204 velocity). I have personally seen 3 coyotes hop up and run off this year shot with V-max bullets out of a 204. Another was shot with a 55 gr V-max out of a 22-250 that the entrance was the size of a baseball. This one was right behind the shoulder at 80 yards. I personally use a 220 Swift with either 52gr BTHP of 55gr SP.