I have had zero results with shot loads in firearms that feature rifling. It is my belief that after pushing through whatever is holding the shot in the shell, the shot just follows the rifling to a very short range oblivion.

Now, a smoothbore .22 rifle behaves much different when loaded with shot, and a snake doesn't stand much of a chance with this combination out to maybe twelve short paces. When I was a kid, .22 smoothbores were cheap when you stumbled on them-now they cost more.
Best,
Ted