We've seen examples of barrels with two different serial numbers or two different Damascus patterns that were apparently at one time returned to the maker to have a damaged tube replaced. It seems to me that if it is possible to mate an original tube with a new replacement tube, it would be just as possible to mate two used tubes.
I'd be interested to hear what you all think of this... feasability,
I am faced with a similar problem right now and have spoken with Doug Turnbull and other expert gunsmiths who have all said that they do not have anything capable of producing the kind of heat necessary to seperate the brazed joints of the barrel breechs and lug area and then reassembling them. Kirk Merrington said that he doubts that he can do it but would like me to send him the gun so he can "look it over".