You are talking different generations of barrels and like most things, you should have second thoughts about trusting
the old. .....
As an example, I had an "old" percussion double, M/L. the outside looked great and the bore was in fair shape or at least I thought I could
work up a light load that would be safe. I had it inspected and X-rayed. There were signs that some of the inner layers were coming loose and flaking. Would have probably
been okay to shoot.
Decided that it was not worth trying. .....
Be wary and;
Be Safe !!!