Same story here - over many years of collecting, first and foremost trapdoors but also Krags, I can tell you that outside condition does not always agree with bore condition.

Many's the rough TD that has been found with (or would clean to) a near-pristine bore, yet I've seen any number of really nice-looking Krags that were total sewers inside. Has to have been something to do with the early smokeless powder and/or priming, and cleaning methods employed.