I'm ready to replace the PSA upper on one of my AR's and I'm leaning Aero Precision. I want something with a stainless 416 barrel and a Wylde chamber that will be accurate. I kinda like their enhanced receiver with the rail threaded directly onto it but I'm not real keen on their large diameter rails, preferring something smaller in diameter like Midwest Industries. They say most BAR style rails will screw on but I'm not exactly sure what a BAR rail system is (unless it just means it screws directly onto a receiver or threaded barrel nut), or if Midwest or someone similar offers something like that that's a lot thinner than Aero's version. I think Aero likes the idea that a suppressor will fit inside the rail but I'm not interested in that.