What worries me with a rifle like this is when you pull the trigger and something goes "pwing". Must be a sickening feeling.

I personally this too much emphasis is put in bore condition, rather than mechanical. The rifles represent some of the highest component stress values of mechanical devices. There is a lot of force crammed into tiny parts. Fatigue is cumulative; breakage is a real prospect.

I think that double rifles will shoot for a very long time "well enough" even with worn rifling.

B.