I doubt they are revolvers. For that kind of work those folks usually go for a .22 semi. And grandma really shouldn't be planning on putting bullets into the back of someone's neck.
Rounds depend big on the owner. If you run in circles under pressure, a .50 isn't going to help you, but if you're a Celt or some other Steely person, a .22 is mighty fine.
This old granny did something nasty to her granddaughter's so-called boyfriend. Now they call her Grambo.