Nit-picking but I don't believe the Winchester 21s were proofed by anybody. I think the barrels were regulated and chokes modified after shooting standard loads in them but I don't believe the 21s as part of the process had proof loads fired in them.
From Schwing's book - I posted the same paragraph on the thread about Winchester chopper lump barrels.
Each Winchester barrel forging had a large long surfaced integral lug. While the idea for interlocking barrels was not new it was an idea that was not employed at that time among other American double gun makers. In addition to this interlocking system, Winchester used soft solder, a mixture of 50 percent lead and 50 percent tin, to join the barrels togeth. Becasue of the strength and reliability of these barrels Winchester was proud to place th Winchester Proof Mark on them. As Edwin Pugsley so aptly put it, "the mark 'Winchester Proof' simply guarantees that it is a heat treated alloy steel of special analysis which is the best that we know at the presnt time for the particular purpose for which it is used."
The footnote to the Pugsley quote says it was in correspondence from Pugsley to Colonel W. F. Sigmund on March 10, 1932.
Last edited by AmarilloMike; 01/05/12 12:05 PM.
