Fortunately I put this on a preban updated with a new RRA 6pos stock. Its a handy piece. I measured the RRA upper as compared to my m4 14.5 upper with a Vortex(new type) on it. The RRA mid-length with a2 flashhider is less than an inch longer.
I really like the increased sight radius, and the weight. The m4-ish feed ramps they cut in were a nice touch. Unfortunately am limited to 68gr or so because of the 1/9 twist. Still waiting for a ACOG 31F. Middies have a reduced peak pressure, which enhances reliability and lessens wear. An additional 1.5 inches of barrel extends the ideal lethal range a bit.
For a shooter that will see more use. I'm going to get another one, with a chrome lined barrel, and send it off to get re-profiled under the handguard like an A2. Then add my Comp2 and some rails to the handguards.
The only thing different about the bolt group is the bolt. It has an slightly different shapped extractor, different spring, and a O-ring.
This is the type of carbine the Marines should of updated to, instead of the m16a4. Well OK a 16&11/16" barrel so they could correctly mount a bayonet.