I bought the same upper. Already had a PSA lower, GI carry handle, and then bought the Magpul brace.
PSA put a nitrided flash suppressor and bright shiny delta ring on a phosphated barrel. Why PSA, Why? The horror! The horror! Also, the BCG was nitrided, It was beautifully done, but I was expecting a mil-spec phosphate BCG, especially with a phosphated barrel.
Thanks to Bigger Hammer on here, who I guess wanted nitrided parts, we traded nitrided for phosphated. Now my rifle matches and is more mil-spec, except for the stupid shiny delta ring, which I will probably change out at some point for a mil-spec one.
The good news is the pistol fires without a hiccup and is the only weapon I have ever been issued or purchased in 30+ years of using these things that the mechanical zero equaled the true 50/225 zero without adjustments. So someone at PSA put this one together right. I have a few other ARs, so the fact I may only get 5-6,000 rounds out of this un-chrome lined or un-nitrided barrel doesn't bother me at all.