You're worrying too much. Just lube up the BCG and throw a few hundred rounds down range, it will break in. I had a DPMS 20" upper a few years back that would hold 1" groups at 100 yards; granted the slightly lower grade 41xx series steel may not last as long a Colt, Lother Walther, or Krieger barrel. But are you really going to throw 10,000+ rounds down range to find out? If you do get that much into shooting it, you'll want a new gun soon any way.
Shoot and enjoy.
>>FN knows a thing or two about military specs and certainly can make M16/M4s to spec.
Yeah, they're probably the premier manufacturer in the western world.
A good point was made in that the deviations in quality between ARs has diminished significantly with even the low end being reasonably acceptable.
Hk USP 45 Expert, USP 40, USP 9, SIG P226, S&W M&P9, Hk 4, Makarov, Desert Eagle 40, Beretta FS92 Centurion, Kimber TLEII 1911A1, Glock 22, SIG P225, 1943 Rem Rand 1911A1, S&W mod 64, Walther PPQ, SIG P229, Browning BDA 45 (SIG P220), Hk45, SIG P230