"Shot and regulated" dealt only with adjusting the chokes, if indeed any was required. The term did not include removing the ribs, etc. It is a oft quoted fantasy that shotgun barrels were regulated by moving the barrels and relaying the ribs. Not so. Only when the grossest error was discovered would such a thing be done. Being a shotgun and not a rifle it is no big problem to get them pointing in the same general direction upon their first joining.

When an old man dies a library burns to the ground. (Old African proverb)