I know that I am probably going to sound like a tard for saying this, but we used to kill rabbits, cats, birds, mice, etc. with our .177 caliber Crossman pump bb guns. We could use pellets in them too but they where expensive for a kid and you could get 10X more bb's for the same money. Idunno, you hit a cat in the head with a bb moving 350fps and it usually goes down. It might twitch a little but it is usually dead with one more shot. We where accurate with our little bb guns and usually killed what we hit.