is there any reason that the rails can't be welded in with a mig welder? Drill small holes in the receiver and then weld through to the rails. I have a mig and don't need a spot welder.
No reason it can't. They referred to that as being a rosetta weld when I started building AKs.
I have a nice millermatic 250 welder. But no spot welder.
I have done exactly like you are talking about on all of my builds so far. I think it looks cleaner sanded smooth on the outsides anyways
Before I purchased my spot welder that is the way I did it...punch and drill the five to six holes clamp the rails and weld the holes shut...grind and sand...
what size hole do you drill for this in the receiver? i too plan to do mine this way.
I forget what size drill bit I used. But I drilled the largest hole I could while still covering it with the rails. If the hole is to small it is hard to get a mig welder to penetrate.
If you welder has a "Hot Start" feature, use it. Migs aren't good at penetrating right off the bat.