A .223 is a pretty good cartridge for coyotes. Most any old bullet will do. I have ruined a few with a Mini, and a couple with a 77 Mk II Rugilator. Right now, I rigged a Colt AR lower with a CMMG upper, flat-top, with a K4 as a truck/coyote gun. 20", 1:14 twist. I use 50- and 55-grain bullets.
But a .243 spreads poor Ol' Wily over a larger area.