Why not somethin like a new 6mm ARC or 243 LBC in a AR-15 platform, or even a 6.5 Grendel if you need something bigger than a .224. Just asking. I used to shoot a 6mm-204 and 6x45mm, abandoned the 6mm-204 barrel and made a 20 Practical out of it and the 6x45 is pretty much just for targets. Now all my coyote hunting is done with the 20 P, 22 Mag, 222 Rem, 223, 22-204, 5.6x50R Mag, 22-250 and 22 Sav Highpower, never had a problem killing a coyote. AR's in 20P and 223.