The only thing wrong with a touch hole as big as those is that no one is happy standing beside you on the firing line. The "backwash" from firing a "flinter" with a touch hole that big sprays the shooter beside you with hot cinders, usually in the face or neck. Of course, that's not as much of an issue with shotguns as it is with a rifle, because with a shotgun there is usually no one standing beside you while you're firing anyway.

May God bless America and those who defend her.