As I had posted in the past I had picked up a RRA ET carbine that was not a chrome line upper.....Well today my chrome lined upper came in and I traded in the orginal upper at no cost! Now I can put on the ACOG TA01NSN and KAC 300M BUIS up top. I had to rob the KAC 300M BUIS off my Bushmaster M4A3 but put a new ARMS 40 BUIS on in its place. The RRA is sure a nice weapon and I hate to say it but seems built as good if not better than my Colt Sporter Match HBAR. I will get back with a range report when the weather eases up here in Michigan.