What shotgun barrel has the biggest bore?

Answer 1

Years ago there were shotguns known as "Punt guns". They were not fired from the shoulder, but strapped to small boats (punts) and used to kill flocks of ducks for sale. No longer legal for hunting, these were muzzleloaders, about 2 guage, and fired about a pound of shot. The largest shotgun that was shoulder fired was the 4 guage. In current US hunting regs, the 10 g is the largest legal shotgun for hunting.