A sample of 12g barrels I have measured
1903 Parker Grade 3 2 frame with D4 damascus
9" from breech L & R .045
1913 Sterlingworth
9” from breech L .040 / R .045
1903 Smith 00
9” from breech L .048 / R .049
1906 Smith 00
9” from breech L .044 / R .053
1929 Smith Field
9” from breech L .043 / R .045
1905 Remington 1894 A Damascus
9” from breech L .060 / R .058
The end of the chamber wall thickness is even more critical. Lots of numbers here
http://www.doublegunshop.com/forums/...=379803&page=3
.025 MWT refers to the distal 1/3 of the barrel; usually reported both 9" from the muzzle and MWT location. Factory small bores may have MWT of .020".
Threaded Mode