erich,
IF you have enough "meat" in the chamber/barrel, you might consider reaming out the chamber/barrel to 10.3x76R (which is nothing more than the 3", .410 brass shotgun shell).. - That was a fairly popular method of dealing with rusty barrels in the 1880-1910 era & the 10.x76mm Rimmed is a considerably more powerful cartridge than the 9.3x72R is, while remaining a "period combination gun" cartridge.
yours, tex
