Ron
My 9 gauge was originally proofed as a 10/9 gauge (each barrel was different). Over the years it was honed out to 9/8.5 with the resulting thinning of the barrels. I "safety" tested it by static firing each barrel with 6 drams of BP and 1 1/8 ounces of shot. I shoot the gun using 3 drams of BP and 1 1/8 ounces of shot (basically, a standard mid-range 12 gauge load). I believe the original working load was something like 5-6 drams BP and 1 3/4 to 2 ounces of shot, so what I shoot is not even close to what the gun was originally proofed for.
That said, you may be able to Tig weld the barrels, have them checked by a gunsmith for thinness etc and if okay to shoot use loads apprpriate to the gun (don't forget, even if the barrels are sound, you still have to worry about recoil damaging your stock, which is the main reason I shoot such light loads).
Steve
