I say this because the welded joint leaves a large area of of the join effectively flapping about.I know this because I have seen how a sleeved tube has blown into a cutter mark that was left when reaming out the original chambers.The soldered joint offers a much larger surface area for the tube to be attached to the existing breech end.A good part of the force from the cartridge when fired is directed outwards against the chamber wall.If the chamber wall is not attached to very much it has the potential to move around especially if it is only welded at one end.The tinned joint means the tube and the breech end are fully attached as if they were one piece.
