Before submitting the following, let me preface by saying that I have not assembled an AK type rifle yet, thus, very limited on knowledge.  I have read the usual method of rivets, which is the same as the production AK rifle.  I have read about using screws to assemble, which, to me, sounds a bit simpler than driving steel rivets.  Has anyone tried spot welding the receiver to the trunions?  File the original rivets flush with the trunion, spot weld over them, and add a few more spot welds just to make sure. 3/8 to 1/4 inch spot welds, or larger, may be able to do the trick?  Is this a viable assembly theory?  Why/why not?

Are you asking about a spot weld or a plug (AKA rosette) weld?

I thought about a rosette weld, but doubt that it would be strong enough to hold the trunion to the reciever, even when using the same four rivets (front trunion).  If it would be strong enough, let me know.

I am talking about a spot weld using eletricity, like automobile frames are assembed, from sheet metal.

In order to spot weld the two materials must be fairly close to the same size.

Your receiver would go into melt down long before you got the trunnion anywhere near hot.

They can and have been successfully rosette welded with a tig

Weld build info