Very interesting!.

When reading this I wonder if they have..

1) ..drilled the barrels sub-bored.
2) ..fired full loads in them.
3)..inspected the barrels for stresses, strechtings, warps, cracks etc.
4)..when the inspection was done and the barrels passed, they stamped the barrels.
5)..re-bored or re-rifled the barrels for the correct boresizes, which also took care
of any indentations made by the stamping tools.

I have read somewhere when proving the blackpowder rifles back then they simply gave them a doublecharge powder + doubleweight bullet. My 10 is not marked with gauge caliber but with the boresize in inches (.793").

Just my one cent..