As to the corrosiveness of black powder, my observations of early
K-frames is that the 1899's and 1902's usually have pitting in the
bore. Much more prevalent than in guns produced after 1910, or so.
Sometime around 1908, the factory no longer considered the use of
smokeless powder to void the warranty. I've always assumed that
the expanded use of smokeless powder, from about 1908 on, was the
underlying reason for the relatively good condition of bores, on guns
made after about 1908 or so.

If one googles "corrosive black powder", there is no end of articles
about this. Its also the case that, at some point, something was
added/changed in black powders, to eliminate the corrosion problem.

Its also my observation that its the early M&P's, and not targets, that
show so much pitting in the bores. This may be because M&P's were
primarily daily carry guns used by police officers, and perhaps they were
not cleaned as often, or as well, as the target revolvers. As a rule,
early target revolvers are in much better condition than early M&P's .

Mike Priwer