They do look like shoe lump, but there is a center seam on the lumps (pic with the bottom plate off) Were shoe lumps soldered together this way as with chopper lumps?

There is a lot of talk about modern steels in this discussion.
I have not noticed that a modern barrel has any more bore life than a vintage barrel - on a Winchester model 70 say.
Knowing the service many classic guns were subjected to, and their longevity with proper care, is the idea of using modern steel relevant?

Also, are sleeved double barrels normally TIG welded at the breech end or the muzzle end or both?
Does the weld serve to function as a structural improvement, or simply to conceal the seam?

I know, a lot of questions - just trying to learn here