In answer to your question re: difference in proof diameters and bore sizes.The right barrel at the time of proof was 13 G [.710 nominal Diameter].There being no choke it was a true cylinder through out its length.The left barrel at time of proof was 12G[.729 nominal diameter] .019 larger in diameter than the right barrel.Per the proof marks,the choke on the left barrel reduces the nominal diameter at its muzzle to 13G [.710 diameter] To better understand allowed variation in diameter relative to stamped bore size, you need to refer to the rules/scale of proof applicable to your gun; these can be found in W.W.Greeners book, "The Gun" on pages 300-302
The difference in bore size is in fact a clue to the fact that gun was made for the trade. The gun, could for example have been finished with both barrels bored cylinder @ 13G; a popular combination in the Victorian era. To convert it to a gun with a choke in the left barrel, all that was required was to open up the left barrel to 12G! This was a method that could be used to minimise inventories and provide quick delivery on special orders.
Last edited by Roy Hebbes; 07/05/09 08:19 AM.
