.710"-.719" is 13/1, not 13... but it depends when it was proofed, because of the introduction of the intermediate bore sizes (when? haven't my refs to hand...); so .710"-.729" is 13 too...! I think...

Edit: getting myself mixed up and will now await correction from a credible source!

Last edited by cadet; 09/17/12 05:28 PM.