Proof is only an internal measurement. Is it within .010 of what it passed proof at? The walls could have been .050 or .020. Wall thickness has nothing to do with proof. Guns have recently passed proof under .020, one I was told had a barrel at 015. I do not know where it was that thin. It could have been 2” from the chokes or at any other point. They do visually check before and after but they only measure internal before at 9”. If not bulges, rivelling or other visual defects occur and they stay on face with no action damage they pass. Now I am sure their visual inspection is 100tikes better than mine would be after thousands of examinations.

Passing proof is a snap shot and give only a little assurance of safety. But it does help you determine if a set of barrels have been honed to death. Nasty pits are hard to remove and require even metal removal from the entire inside area so as to not create a weak section on the barrel wall. If one side was .035 and the other side was .015 you can foresee a real issue. But in proof is one standard we like to know. Wall thickness is another.


What happens later is another matter. If you have a dent or bulge the barrels will suffer metal loss as that is corrected. If you have pitting, internal or external, that may require metal striking or honing to clean it up. That will also require metal to be removed and a thin area. When I see a gun at proof dimension of .720 that remains at .720 that has an area of wall thickness of .020 I pay close attention to location and to see if the entire barrel in that area reads the same or if it is localized. That .720 was measured at 9”not everywhere.

Size does matter. Location matters. Was it a dent lifted, then struck before refinish? Does it run the same from top rib to under rib? The gun remains in proof. A dent will be thin in one area and thicker near the ribs. An internal cleanups are more even in all directions. You home a perfect circle but strike a area down in one localized spot. Trust but measure and if it seems odd ask others or better yet just walk away. Odd often is a warning that you need to take heed of.