I've just started reading this thread and I see there are 4 pages already ahead, so forgive me if my suggestion has been covered.

Although I'm as close to useless on any gunsmithing duty, I wonder if it might be possible to, instead of sleeving the barrels, to find a set of damascus barrels in excellent condition and somehow FIT them to the gun in their entirety as REPLACEMENT barrels, as it were(?)