I once saw my brother shoot a squirrel in a pignut tree, with a high-brass 12 gauge load of #6 shot. As it fell it wedged in a fork in the tree. He couldn't climb up to get it or shake it loose, so he shot it again. And again. And again. Five more times, before it fell out of the tree. When I picked it up it felt like a wool sock full of raspberry Jell-O.
.50 BMG might have been cleaner.