Photographing lots of shotguns, lot as in thousands, my observation is that most double shotguns have muzzles that touch and the spacing ot the breech ends depends mostly on the type of construction. Monobloc barrels impose wider spacing at the breech than chopper lumps. With chopper lumps there can be filing in the inner surfaces before brazing. This brings the central axes of the barrels closer than in monobloc construction. Despite these differences in convergence both types seem to hit OK on the pattern board.
