I want to try squirrel hunting. I have never done it before.

The place I was going to try only allows muzzleloaders and shotguns. I have 12 gauges but don't think the boy would care for the recoil, muzzleblast and weight. I don't care to haul one of those heavy rigs either after back surgery. I am thinking of cheap light weight single shots. My question is - is a 410 enough for tree rats or should I get 20s?

All my muzzleloaders are big bores and the cap and ball revolvers are not considered muzzleloaders.

Any other suggestions would be appreciated.