We have to use a shotgun where we hunt it is on a refuge and they won't let you use
a rifle.

My favorite shotgun for squirrel is a 20 gauge. A 12 gauge is too heavy for me. I cannot swing a 12 as fast as a 20. This causes me to lose the squirrel before the shot is made. A 12 gauge is fine, but I like the weight of a 20.