I know the general concerns about shooting Damascus and then combine that with extreme age plus barrel wall thickness plus pits, dents etc. and you end up with a dicey proposition. This is also assuming only shooting moderate to light black powder loads.
My question is only concerning chamber end issues.
No one here can accurately answer your questions without knowing the condition of your barrels. Age alone does not appear to deteriorate Damascus barrels, but severe deep pitting, dents extending into the bores, and inadequate barrel wall thickness certainly does. The presence of any pits, dents, or thin walls is also more critical the closer they are to the breech end of the barrels.
There is tons of evidence that sound Damascus is safe to shoot with appropriate loads. But that is my opinion based upon my own experience. What you decide is entirely up to you.
Normal brass shells, or paper, or plastic do expand to seal the chamber and direct gasses down the barrel instead of leaking past the shell and hitting the shooter in the face. Then they rebound enough to permit extraction. Even if you made extra thick brass shells, you will still have peak, or very near peak pressure exerting force upon the barrel as soon as the wad passes the end of your shell and entering the forcing cone. But then, depending upon the thickness of your custom brass shells, you could also have undersized wads entering the forcing cones, and possible gas blow-by that would cause a reduction in pressure and a disruption in the ballistics. Of course, some folks are happy with the performance of sub-gauge inserts, but I have no personal experience with them.
Short answer... just have the barrels evaluated by someone competent and experienced in this area. Not just any gunsmith can do this. Some who don't know better are of the opinion that all Damascus is junk, suitable only for making table lamps. They might advise you to scrap a perfectly good and safe gun. If a competent gunsmith experienced with evaluating Damascus barrels says the barrels are sound, then shoot them with RST's or similar low pressure loads. Otherwise, retire the gun and buy something safe to shoot.
