My experiences with NEA are the following:
1) Bought a stripped upper, rail ok, held the barrel just fine, no complaints
2) Bought a stripped lower, also no issues with the dimensions. The only weird things were the fixed trigger guard and that the takedown pin detent goes up from the pistol grip
3) Ran a 22lr upper, gave me a bunch of light strikes, but so did my CMMG upper, a weakness of the system itself, not the manufacturer. Ordered aftermarket parts to fix those weaknesses on the CMMG from Cactus