I do use smokeless loads in damascus or Twist barrels with not much worry about their use. I would however like to make two comments to this thread.
1st; The type of powder originally used cannot be determined by the present condition of the bores. most users of quality guns in the black powder days understood the need for proper cleaning. The corrosive salts left by early primers was actually worse than that of Black Powder. The normal cleaning methods for BP took care of the primer residue as well. With the shift to Smokeless many were negligent in their cleaning. Consequently many early guns with pitted bores are more of a result of early Smokeless Shells with their Mercuric primers than actually from the use of Black Powder.
2nd; As long as an adequate wall thickness is present the actual "Boring" has little to do with the strength of the barrel. Many of the early guns were "Over Bored" for the use of all brass shells with oversize wads which were popular among black powder shooters who loaded/reloaded their own shells. I the early years reloading paper shells with Smokeless was discouraged. Thus guns intended for use with "Nitro" were bored closer to nominal gauge size for use of factory paper shells with standard size wads.
The fact they were advertized for such use of course indicates they were approved for use with smokeless, but the boring itself did not give an increase of strength.
