177 fastest most accurate

Rats, Squirrels, Opossums & Snakes.

Why you killing oppossums? They in your chicken coop? Leave those alone as long as they aren't being destructive. They will eat more bugs, slugs, and rodents than you can imagine. Ugly as home made soap, but usually not a bad neighbor.

For the rifle? Can't help you. I like .22. Seems you are caught up in the speed trap though. Much over 900 fps, and they can get unstable, so read closely here, these folks seem to be giving out solid advice. Not always a common event on the internet.

Happy Shopping.