a higher powered air rifle should kill a snake, HOWEVER, the higher powered the more noise it makes. We've got one, and its not even THAT high powered, but it sounds like a "real gun" when you shoot it, so if the worry is the neighbors freaking out over gunshots you might be out of luck.
I DO suggest, if you get one, make sure its NOT a one shot gun (mistake we made) and make sure its either easy for you to pump up quickly for the next shot or uses CO2 canisters.
---------- Post added at 06:30 PM ---------- Previous post was at 06:29 PM ----------
I'd suggest your local sporting goods store (not walmart), ask questions, explain what you want, take notes, and go hit the 2nd local sporting goods store and repeat, and compare the answers.