Was recently watching PA outdoors and was surprised at the # of youth hunters that shot deer with a .223. If a .223 can kill a deer it certainly can kill a coyote, shot placement and bullet type are where to start. If you want to go bigger I would go to a .243, and if that doesn't work my next choice would be a .35 Whelen loaded with .357 240gr Hornady XTP jacketed hollow points, they shouldn't go anywhere then! laugh