Is there any appreciable difference between these rifles? Is one any better built than the other? Thanks in advance for your opinions.

RRA has a better trigger , better sturdier free float tube and a hooded rear apeture.

Both are very capable accuracy wise but the RRA has better features you will appreciate in the long run.

Quoted: RRA has a better trigger , better sturdier free float tube and a hooded rear apeture. Both are very capable accuracy wise but the RRA has better features you will appreciate in the long run.

Well said.

I would also point out that the Bushmaster two stage trigger is pure crap. You will end up replacing it, I have seen no less than a dozen crap out.

I also think the Rock River has a better chamber. RR uses the Wylde reamer and Bushmaster uses a CLE. The CLE tends to be a bit tighter and a bit more finicky with regards to reloaded ammo. Tighter does not necessarily equate to better accuracy either.