I've killed most of my coyotes with a 223, using mostly 50 grain VMax bullets. Never really felt as though it was lacking. I've also killed quite a few with a 243, and some with the 22-250. While the 223 is certainly enough, performance wise, the 243 and 22-250 are better, especially at the longer ranges. A 40 grain bullet out of a 22-50 at 4000fps will absolutely put the hurt on a coyote, as well as a 58 bullet out of a 243 at 3800fps.
