I have kept track of every round I have fired thru an old Bonehill 12 Ga. that I believe was built around 1905 with damascus barrels and the bores honed to .735, and experienced my first failure last week. Each year at this time I total up the amount from 2004 and it is 18809 and at 18720 the link between the tumbler and main spring broke on the left barrel. Just for your information, next year I will post again with an update.
See Ya,
Bonehill