A gun is out of proof if a plug .010 larger than the plug used to determine bore diameter goes down 9” where the bore is measured. So a gun with a .720 bore is still in proof if a .730 plug will not go the full 9”. It might be .728 or .729 and if the plug won’t go it is still considered in proof. Also any alteration of chambers will put it out of proof. So if the barrels start out at .025 thickness and gets cleaned up to .008 to remove pits it still is in proof. But and this is a big, but the wall thickness may have gone from .025 down to .017. Thin but still in proof. ...
This statement is not correct. If the bore of a gun is opened or honed to an inside diameter. 008" larger than its' original proof bore diameter, it will still be in proof, as stated. But the barrel wall thickness will not be reduced by .008". On average, the wall thickness wiil only be reduced by .004". In this example, the original wall thickness of .025" will not be .017" after reaming or honing, but more like .021". That's a significant difference.
I am curious about the location of the area in the barrels mentioned that have a .006" MWT. I agree with Ted and Fudd about them being both very compromised, and scary too. I don't want even 1000 psi of powder gasses abruptly escaping anywhere near my eyes or fingers. There are too many perfectly sound guns available to risk using one with barrels that are soup can thin.
