L.Brown, This gun was heavily pitted but with very good MWT's and substantial metal in the chamber area. To remove the pitting, the barrels had to be lapped to beyond their proof size so it HAD to be re-proofed. Given the nature of the 2 1/2" and 2 3/4" proof tests (see above), it was a no-brainer to lengthen the chambers. So when the gun was submitted for proof, it had 70mm chambers, the gun would have been measured at 'view' and when the gun failed (or passed) the paperwork would record it as a 12/70. It would not have to have ever passed 70mm proof to be ticketed as such.
Toby--Thanks for the clarification. I think many of us have seen guns that are out of proof due to bore diameter, but with good MWT are very likely perfectly safe with appropriate loads. As this one might well have been, had you not been required to submit it for reproof.
Craig--As pointed out above, although you can't cure stupid, you can deal with ignorance via education. And this BB is a good place to get educated about vintage guns. Even some vintage American guns with factory 2 3/4" chambers aren't necessarily safe with every American factory load. Without a careful inspection, preferably by a gunsmith who knows his way around vintage guns, the average shooter has no real way of knowing what kind of life that gun has led since it left the factory. But unfortunately, a whole lot of Americans will take that 2 3/4" mark as a guarantee that it will work just fine with the heaviest and hottest off the shelf loads.
