I spoke this morning to a UK barrel maker who is routinly TIGing sleeved shotgun barrels. It does involve complete disasembaly of the ribs. Shotgun barrels however are of a lessor grade of low carbon steel.
As Tinker wrote, and I suspected, it cannot be done where a conventional method involving soft solder has already been used due to weld contamination. Following the TIG the weld area is then torch annealed. I do not work on shotgun barrels so in this regard I will have to bow to the experience of those that are doing so.

We spoke then about doing the same for rifle barrels and due to the alloy steel the jury is out. It has been refered back to the specialist welders that actually carry out the shotgun jobs for their comments, the people that I spoke to had never attempted it with DR barrels. I will post their reply when I get more information.

My read on this would be that it would be more economicaly sound to build a complete new set of chopper lump barrels than engage in a make do and mend on a set like this. As the work involved to do it properly would be similar in hours expended and one would still only end up with a set of sleeved barrels.

JPK did state that "Barrels are not hardened so I can't imagine that is any issue". In the case of rifle barrels that is not so. Rifle barrel steel has an average hardness of RC 25-30 I believe that some from various manufacturers can go as high as RC 37-8. There is a well documented embrittlement problem with 4140 @ the 500 degrees transition. I can see no way that normalisation of the material can be done without reassembly as it is above remelt temp of the spelter.

Regards