Bac in the hay days of barrel sleeving in Birmingham ,that the late 60's .Tubes were in short supply and as a rule Brummie gun men did not spend money if they did not have to . As a result of this there are a lot of old barrels stripped down and the tube reused .Some were barrel that had for some reason never been finished or that had failed proof on one side and were put aside as nothing was ever scrapped . Greener had a great many that seemed to disperse into the trade ans there were Fire damaged barrels that had come out of the old Midland factory . Yes I have done it myself in the past . It was not uncommon to find a cheaply sleeved gun that had one steel tube and one damascus !
Point being that if you can find a good set of damascus barrels then yes it is possible to take them apart and reuse the tubes . But you have to be very careful and measure up to make sure before you start .Nowadays I would be reluctant to take such a job on and if I did it would be on the script understanding that the outcome of the finished job would not be guaranteed .
Sorry Toby but I think your idea of "re-lumping " is a non starter as I can see so many problems ,believe me having fitted a new lump to a set of barrels in the past I can assure you it ain't easy .
