You can't prove that the parts PSA sells are not the same parts BCM sells, either. Just because you're willing to pay more for the name does not make the parts any different regardless of how much you wish it to be true.
That isn't entirely true. Hear me out - I'm not trying to argue on this one, just get more information in peoples hands.
If you look at LPK's from a bunch of manufacturers you can clearly tell that a) there is one company making 8/10 of them....and b) there are 4 or 5 companies making the rest.
Of those 4 or 5 making the rest, some are fine (aka probably won't kill you) and some suck a dead donkey dick.
I have built a few PSA's. The last PSA had the dead donkey dick LPK parts from the factory. The rest were fine. It was so bad the rear takedown pin would pivot when you pulled it out because the track was cut crooked.
One easy way to tell that you have the donkey diller special is the little springs that go to the take down pin retaining pins are coated in some black shit and not silver.
I'll also circle back. The parts that seem to fuck people are the BCG, barrel, and buffer tube. On occasion the lower has the mag catch slot cut in the WRONG position.
As for BCG's, there are only a few I really like. Mil-spec rock-stock, and some of the Gucci shit like a JP, LMT, KAC. I found the suppressed setting BCGS like the RCA and Gemtech were also pretty good. I really like the surefire OBC - seems a good middle ground and comes with a good spring and buffer.
You can tell its probably a mil-spec one by the chrome lining in the bolt bore of the carrier. The interior of the bolt bore should be mirror smooth.
As for the barrel, massive overpassing, under gassing, and shitty chamber work seem to be the majority complaints.
And finally, buffer tubes are all the fuck over the place. Get a 7075 tube that has a smooth inner bore. Many companies don't finish the surface in there and it does reduce your budget for fouling in the system. BCM, colt, etc run smooth because the BCG bore and buffer tube bore are like glass. You can feel this part with your finger. Jam it in there like its a vagina and see if you feel heavy machining marks. If so, pass on it.