Daryl, I feel your pain. Most dealers don't have the equipment, knowhow, or maybe the sense to measure bore dimensions. What I don't understand is a dealer that deals in very expensive shotguns, and has a large inventory of them, and can't or won't measure dimensions. He's either stupid or crooked. The Brits have got all their proof laws set up the correct way. If you sell an out of proof gun there, you pay a hefty fine or lose your license. A good percentage of our dealers wouldn't be in business two months if that law was equally applied.
it's probably worth noting here that British proof rules don't automatically determine that a gun is out of proof based only on barrel wall thickness. Guns are out of proof if the bore diameter exceeds the standard for that particular gauge by more than .010 inches. While that does not tell you the minimum barrel wall thickness, it does tell you that the bores have likely been honed out significantly and makes it more critical that you should definitely measure barrel wall thickness. Christopher Austyn, who headed the sporting gun department of Christie's when they were still in the firearms auction business goes into some detail on the issue of barrel wall thickness in his book "Modern Sporting Guns" (1994). He points out: "There is no legal minimum thickness for a shotgun barrel, although the Britiish Gun Trade Association recommend 20 thousandths of an inch as a general minimum."
