It's been talked of before,,
Too many complications with the heat of welding and proper temper to maintain safe conditions, the general concensus is a thumbs down to the welding issues on barrels. Sure it all can be done,, but boo-coo bucks unless your a pro shop with all the equipment.
Much easier to thread the ends and screw into a proper receiver. So guy's find shotgun barrels, stub and thread an,,et al,,