While these dias are mathamatically correct & those given in rules of proof, there is a "Fly in the Ointment". The 4ga chamber dimensions were set using a proper 1.052" bore but with a thin wall brass case. 4ga guns made for use with paper cases had the same chamber, but bore dia was dropped to about .935" to accomadate the smaller wads used with the thicker walled cases. These guns will normally be found proofed as 6ga. The 2ga was/is normally a true 4ga bore but with enlarged chamber for a paper case of larger size. These guns are proofed as 4ga, but chamber the 2ga shell.
PS; British rules of proof 1868, in force till 1904, Start with A ga @ 2.000" dia & go down through 50ga @.453" dia with every size having charges listed for both provisional & definitive proof. 2ga is listed @1.325" dia. This may well be the size of bore for "Baby" but is not what later 2ga guns were made as. The alphabeticalsizes are simply assigned sizes & drop in 1/16" increments down through P @ 1.250" with G, I & N not being used. 1ga through 50ga can all be mathamatically calculated as are ased on "actual"? wt of lead.
Last edited by 2-piper; 01/28/07 12:36 AM.
