To answer the question about what is the "NEW RRA NM Rear Sight". It is a special designed A-2 NM Removable Sight that is acceptable for DCM Competition at Camp Perry and other events. It certainly has NM Spec parts in it. And can be ordered with 1/4-1/4, 1/2-1/2, or 1/4-1/2 elevation and windage adjustments. But what makes it different is the design of the interior. When the DCM/NRA and competition groups authorized the removable handles use for matches only a few years ago, there was a problem that no one had thought about. Since they needed to shoot up to 600 yards at Camp Perry and similar events, they could not have enough elevation on the sight to get up to 600 yards for competition. If they modified the rear sights to go to 600 then they could not get them to come back down to 200 and lower. So Rock River was the first to design the New NM Removable Carry Handle that would go up to 600 and come down to 200 or less when needed. It is all done via tolerance, design, and modifications of the internal parts although they look similar.
That upper that JonM got is one accurate upper! It is the one used on all of the Rock River National Match Rifles that are sold and used at Camp Perry.