Barrel wall thickness does not take a gun out of proof to be accurate and fair. I am more concerned about the wall thickness and safety in use, than being in proof which is why I measure the wall thickness in the first place. But when I measure a gun and find very thin walls I suspect it has been honed. If you then measure the bores and find it is now with a bore too large that it is in fact out of proof under US proof law, which does not exist on proof issues it is a non issue. But you can not sell or export a gun you know to be out of proof if you are a dealer in Great Britain as I understand it. In fact the auction houses refuse sell out of proof guns unless they have been cut to prevent their use.
None of the guns I've imported have been out of proof unless it was some technical issue I did not know about. But what if one was? Would you first contact the seller or the exporting dealer or just forget about it unless the gun is of substantial value?
