What kind of range are we talking about? if it's a few feet and you have a .357 or .44 cal revolver I would suggest a load of snake shot~don't laugh I've killed both a possum and a groundhog with a .22 snake shot at around three feet!

I find at that close a range the capsule that the shot is in goes through the chest wall and then falls apart inside and just makes a mess of their guts,lungs,heart so it works.

That is with a .22 mind,the larger cal shells should be even better.