Chuck - the engineering info you present is both spot on and quite correct. I would not, however, rely too much on it in the context we're talking about: a bulged barrel. The long and short of my reluctance (or objection) is that the information you're presenting is derived from carefully prepared laboratory tests run under controlled conditions. OTOH getting a gun to the stage of having a bulged barrel and now deciding whether to use it are not. They don't even rise to the level of a shadetree gunsmith tying a gun to a spare tire and firing it with a rope to see if it will blow up.
Other than illustrating ... something ... comparing a double with a bulged barrel to a Model 12 or other single-barrel is inapposite. There's a lot more going on with the double particularly, as noted above, under the ribs. Moreover, comparing this gun - with the bulge in the area of highest pressure 1/2 inch past the chamber - to any gun with a bulge near the muzzle - the low-pressure end - is likewise inapposite.
If the gun in question is to be used, it needs to be rebarrelled. Period. If that's too pricey, the guy intending to use it should price hand surgeons for comparison, then think again.
