Springfield Armory and Norinco M1A parts interchange

[Mojaveman]

Are the parts from a Springfield Armory and Norinco (Chinese) M1A interchangeable?

[Batman]

Well, it depends! What are you looking to do? I've got a Polytech M1A that I've replaced both the barrel and bolt (but had a gunsmith do both). I had Ron Smith do the heat treatment on mine. The rifle has a Springfield scope mount. The trigger group is effectively the same, as are the flash hiders. Stock is the same.

[Sailormilan2]

As “Batman” said, “It depends”. The castle nut threads are metric on the Chinese made barrel. But, supposedly, the threads are soft enough so that they will conform if a US made castle nut is used.
The “buttress” threads on the chamber end are reportedly, metric, but so close to the US size that they will interchange. The gas cylinders are the same size, but the pistons are different sizes. So, they can’t be interchanged. I don’t remember about the gas plug, but probably the same works for it.
The hinge pin for the mag release on the Chinese made rifles is solid, and a slightly different size, so that the US made roll pin probably won’t work. I’ve never had to remove mine, so I don’t know.
The Chinese connector lock pin is shorter, and slightly smaller. A US made pin can work, though it needs to be slightly turned down. An easy job.
I’ve seen some discussion that there might be some dimensional differences in the receivers legs, which may (MAY) cause some issues with SOME stocks.
A US made bolt may not fit well with the Chinese made barrel and receiver assembly, without some modifications.
The legs of some Chinese receivers may not work well with US made stock liners.
But, if you know the issues, and most are easily correctable, then the Chinese rifles are good, and most US made parts will work.