Thanks Dean,
That is exactly what I was looking for. I know what the old literature says about minimum safe wall thickness 6" from the breech--about .090 but I can only speculate that guns with .040 to .050 might be safe to shoot as well with low pressure loads. I will measure my other two pattern welded barrels and post those numbers tonight.:) Thanks for all the others comments as well. I am hoping more people will post their measurments so we can see what difference between guns and gauges are.

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 ;)

http://pic20.picturetrail.com:80/VOL.../408932781.jpg

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

http://pic20.picturetrail.com:80/VOL.../409066906.jpg

More infro here
https://docs.google.com/document/d/1...vwLYc-kGA/edit

great info Drew. Thanks! I promised I would take measurements on my other two Parkers...so here they are. 1. 12 gauge grade 1 lifter mfg. in 1877. RIGHT BARREL .130 WT at forcing cone. LEFT BARREL .128 WT at forcing cone. This gun has the largest wall thickness I have seen on a 12 gauge Parker with twist barrels. 2. 10 gauge grade 3 lifter RIGHT BARREL .096 WT at forcing cone. LEFT BARREL .090 WT at forcing cone. The left barrel has a slight .004 bulge at the forcing cone which is hard to see but it is there. Thanks for taking the time to measure your guns. Keep them coming!:rotf: