I believe the only knowledgeable AR shop may very well be Rainier Arms LLC. in my neck of the woods.
One place I went to (not RALLC.) this one fellow told me that if that "electronic fandangled thing" (Aimpoint.ML3) on my rifle "crapped out, then you're SOL and the rifle's useless because there's no way to use any sights." Mind you I have BUIS. He was also wondering where the carry handle was and wondered if I had it "chopped off!" After that, I took my leave. No kidding on that experience.

