I think I'd go for the Varmint Grenade first, to see how it worked. As for what'll put a coyote down, I've used the Nosler 40 gr Ballistic Tip and it'll flatten a coyote so fast you'll think you missed. And I've used the Nosler 55 BT in the 220 (messy). And I've used the 100 gr BT in the 260 and surprisingly it didn't make that big an exit hole in most cases.