Have you borescoped the barrel in question?
I don't have any particular minimum accuracy for my AR15s, but I did do a lot of testing on what is the "inherent accuracy" of many of my ARs, including a couple of that I still own. The basic barrels that I have from BCM, Colt, and LMT have all been excellent, plus a DD upper that I sold off. I put them in a Lead Sled and 2-3 MOA was easy with 1x red dots, with less with a magnified optic.
I have a PSA upper, but that is my "beater" upper that is meant to test shooting all sorts of crappy and underpowered ammo. I haven't tested it like the uppers above.