Long time lurker, newly registered.
I put together an A2 upper from CDNN last month with a Rock River stainless HBAR 20" barrel with A2 front. It is an absolute tack driver of a rifle. (National Match free float tube, 2 stage trigger, A2 stock with 3# weight, M 1/4" by 1/4" sight) And would absolutely recommend that barrel. Currently they have an 18% off inventory reduction going on so the good price is a great price IMO.