Much of the rest of the world's knowledgeable doublegun builders (shotgun and rifle) and smiths use the term "regulation" to refer to where the individual barrels deliver their payload in relation to each other. What is strived for is that both barrels shoot to the same point of impact at a certain distance. gunman, in his above post, seems not to ascribe to this, preferring to relate regulation to pattern percentages at a certain distance. A simple search of the internet for "barrel regulation" will provide an abundance of evidence, and information, about how barrels are regulated to shoot to the same point of impact. Double rifles are much more finicky about this, most having to be used with a particular load in order to deliver bullets to the same POI.
If a shotgun is regulated to shoot both barrels to the same point at, say 30 yards, when manufactured by the maker, it will usually continue to do so with the chokes opened up, providing that the smith who does the work is knowledgable enough to pilot the choke reamer with the bore axis. Nonetheless, he should check for regulation before and after the work is done, as a matter of professionalism. There is a chance that the barrels were not properly regulated when he received the gun, and some will test fire it before doing the work to see what they are working with. Sadly, many gunsmiths don't care about such critical details. Better doublegun smiths do care, tho'. There are several who post on here that have very high standards for their work.
SRH
