Over the years I have acquired a large collection of 'good' damascus barrels in the hope that I would find a set that would fit onto another gun (with a modicum of work), replacing the damaged/sleeved/shortened/whatever barrels that on it.
Sadly this has never worked out.
Given the multitude of different barrel makers and actioners back in the C19th, who all seemed to work to a different set of 'standard' dimensions, perhaps this was never going to happen but I lived (and live) in hope that one day....!
The essence of the problem seems to be that the barrels, action and forend interact is many subtle ways and even when one finds that one set of dimensions look promising, another aspect makes the whole job extremely challenging. A hammergun should be the easiest option as there are generally no ejectors to worry about but even then, short of putting in a whole new set of lumps, there seems to be very little actual compatibility in guns that look superficially very similar.
I have no doubt that a genuine, highly experienced barrel maker and actioner, working in collaboration, could achieve what a lowly gunsmith such as I would baulk at but could they be bothered? And would it make economic sense?
Interesting thread none the less!