Even if you had access to tubes made of earlier low alloy steel, the TIG weld joint would still have a Heat Affected Zone (HAZ) after welding that would have an altered metallurgy. I am absolutely NOT saying that TIG welded sleeving jobs are undesirable. But I've always been concerned whether the gunsmiths who do it fully understand the potential risks. I've told the story here of being totally blind for about a half-hour after a complete head separation on a .22-250 rifle. Anyone who experiences something like that has more respect for these kinds of things. Personally, I dislike seeing the joint of soldered jobs even on new manufacture monobloc guns. Some are very well done by real craftsmen, and some are butt-ugly. The jobs with the turkey-track engraving intended to hide the joint just scream cheap and dirty.
The idea of TIG welded sleeving joints is very appealing for obvious reasons. For proof that it could be done safely, one need only to examine the barrels of Thompson Center Contenders and Encores. The interchangeable barrels of these guns have the barrel lugs welded directly beneath the chambers of some pretty high pressure center fire cartridges. I would bet that there is some carefully controlled post weld heat treatment done to these barrels after welding and before chambering.
