I said he was good, didn't I?

You see, IF the carbine WERE O'Neill's "as issued" piece, the value would be - who knows? $500K?  More?

Well, it isn't - But, what DO we have? At the very best, McNeill's receiver and a bunch of parts. At the worst, an attempted fake/fraud/whatever. NOT saying you did it. It's a puzzle - the potential gain is WELL worth doing a MUCH MUCH "better" fake, IF that was the assembler's game. Certainly does appear to be a thin-wrist stock - correct for number, but not date.

There is nothing "faint" about the stamping on either side of the "weld". Your gun is in fact better (deeper) stamped than the other, so, what's wrong in the middle? Are there any other signs of possible welding inside or out? Odd location for any sort of sight holes, so perhaps a repair?

Interesting thread - ball is in NMM's court, I guess.