You must not have owned NEA then...
I've owned NEA and still have a rifle with some of their parts. My upper/lower and BCG have functioned perfectly and accept any brand of parts I've tried in them. I started with a Daniel Defense LPK then swapped in an ALG trigger, I have a DD buffer tube and barrel nut. I've had 2 different barrels in it as well (a custom 300BLK and a Bushmaster 5.56). Troy Alpha forend and now a AP customs carbon fiber forend. Everything has gone right in with no modifications. I've also had a couple different charging handles in the upper without problem. Buy a Norinco and try to do the same with that many different brands of parts.
What really puts NEA miles above Norinco is that even though a few guys have had problems with NEA at least they have a warranty and the company stands behind it's product. If you buy a Norinco and get a lemon you're on your own to try to make it work or buy another one. Plus NEA has been making corrections to their products and their newer stuff is much better than what they had a couple years ago.


















































