Barrel welded to receiver on No.4

[Sapper740]

An acquaintance asked me to check out his father's "Lee Enfield" rifle that hasn't been shot in almost 40 years and I was surprised upon first look to see the barrel appears to be welded to the receiver on his scrubbed No.4 Mk I. He wants to start shooting it so I offered to check it for headspace, bolt lug engagement, and barrel condition. The #1 bolthead closes on a field gauge but the lugs engage evenly. The bore is dirty but the rifling is a 7 out of 10. However, I am greatly concerned about the barrel welded to the receiver and in an abundance of caution I'm going to tell him to not ever shoot the rifle again. I'm interested in hearing if anyone else has seen a N0.4 barrel welded to the receiver and the possible woes it could be hiding.