There's a lot that can go wrong even if you start with Shilen blanks.
Thing is these companies only build to the specs of the customer. You don't automatically get the other company's product for less. Like FN only makes the CHF barrels to the grade that PSA pays them to. Or BHW to Rainier's specs.
Rainier has a good rep though, and more deserved than some. The 10.5 Select grade I have on my pistol build has been excellent. Feed ramps line up with a quality upper's ramps, barrel fit way too tight into upper, but that's an issue with the upper on every dimension, accurate, the Rainier BCG functions perfect in it (highly recommend over the AIM or others for your build), and everything else has been good. Barrels are dimpled for a gas block. Recommend Seekins adjustable block.