http://parkerguns.org/forums/showthr...096#post158096
http://parkerguns.org/forums/showthr...?t=1565&page=4
English:
James Purdey (1898) 12b., 2.5" chambers: ≥ 0.100.
James Woodward (1909) 12b., 2.5" chambers: ≥ 0.098
James Woodward (1909) 12b., 2.5" chambers: ≥ 0.103
Boss (1897-8) 12b., 2.5" chambers: ≥ 0.090
Westley Richards 12b., 2.5" chambers: ≥ 0.090
James MacNaughton (1895) 12b., 2.5" chambers: ≥ 0.095
Wm. Pape (1898) 12b., 2.75" chambers: ≥ 0.100
EM Reilly (1887-1904) 12b., 2.5" chambers: ≥ 0.091
Henri Egg (1870) 12b., 2.5" chambers: ≥ 0.108
WH Monks (1875-87) 12b., 2.5" chambers: ≥ 0.116
WC Scott (1905-6) 16b., 2.75" chambers: ≥ 0.105
Westley Richards (1905) 20b., 2.5" chambers: ≥ 0.098
WW Greener (1922) 20b., 2.75" chambers: ≥ 0.098
Belgian:
Francotte (1894-5) 12b., 2.5" chambers: ≥ 0.085
Francotte (1896) 12b., 2.5" chambers: ≥ 0.085
Francotte (1930) 20b., 2.5" chambers: ≥ 0.095
Francotte (1938) 12b., 2 5/8" chambers: ≥ 0.098
French:
Verney Carron (1950s) 12b., 2 5/8" chambers: ≥ 0.100
German:
Wilhelm Brenneke (1902) 12b., 2.5" chambers: ≥ 0.110
U.S. maker's doubles usually have a wall thickness at the end of the chamber of > .100
10g and Field grade 12g, and those with a "Double Thick Nitro Breech" frequently much more
Note: In heavy barreled turn-of-the-century U.S. maker 12 GAUGE doubles, the angle of the forcing cone is usually greater than the taper of the exterior of the barrel, so it is not uncommon that the
forcing cone WT is the same or greater than the
end of the chamber WT. THIS MAY NOT APPLY to small gauge American or lightweight British doubles.
WARNING posted on DoubleGunBBS in 2017
“For many years I measured the ID and OD, subtracted and divided by two to get the wall thickness thinking this is close enough. I purchased a wall thickness gauge and began measuring my barrels. One of my guns measured .014 thickness whereas before I thought there was about .025 minimal wall thickness.”
The problem is eccentricity. Freshly cut barrel segments in preparation for tensile testing and composition analysis
More infro here
https://docs.google.com/document/d/1...vwLYc-kGA/edit