Some serious misinformation here. First, 13/1 did not exist in 1880. Fractional bore sizes first appeared under the 1887 rules of proof. Second, if it's marked 12, then it would have been proved as a 12, not as a 13. It would only have been proved as a 13 if it was marked 13. With the bores currently being 733 and 737, it would be marked 12 even if it has been reproofed.
Photos of the barrel flats would clear up any questions about proof/reproof.
Re pressure and barrel wall thickness, the graphs I have--from Dupont in 1933 and from Sherman Bell's "Finding Out for Myself" DGJ article in 2002, show pressures significantly reduced at 9" from the breech. The Dupont graphs show them between 3500-4,000, while Bell's graphs have them even lower: 2-3,000. I expect part of that difference is that Dupont was measuring LUP with the old lead crusher method, while Bell was measuring psi with electronic transducers.
Anyone have a reference stating that .045 should be the minimum at 9" from the breech? Thanks.
Last edited by L. Brown; 02/12/13 08:52 AM.
