The barrels have been honed and possibly the chamber lengthened from 2 5/8" to 2 3/4".
At least an estimate of the length of the forcing cone would be very helpful.
The "end of the chamber" is clearly the breech end, not the forward end immediately before the forcing cone; and
that is the critical number.
I can only assume that the thickest part of the F.C. is .169" and .170" and the toward the muzzle end of the right (I'll bet lengthened) F.C. is .076".
If that number is actually the end of the chamber the barrel should not be used, with
any load.
This helps show that the WT of the F.C. is usually greater than the end of the chamber because the angle of the cone is greater than the external taper of the barrel
I would confirm
1. What was the WT at the (
forward) end of the chamber? (which BTW is that .105" recommended number)
2. What is the estimated length of the F.C.? (After looking down the bore of lots of barrels it's not that hard to tell the turn-of-the-century 1/2" - 5/8" cone and a lengthened cone.)
The CIP recommendation for "standard steel" (something like 4140) at 4" is .075", but pattern welded tensile strength is a little more than 1/2 of 4140 so .076" would certainly be considered low, and 4" is pretty close to some important body parts. I would most certainly only use low pressure loads in the right barrel.