I have a Colt kit. With my 1:9" Bushmaster 20" barrel (post ban- no flash hider), and a carry handle type A2 rear sight (detachable), I get near perfect reliability (I have had one failure- not including ammo related misfires). This reliability was proven with several high velocity rounds (the kit is high vel only), including Remington Golden Bullets, Winchester Xperts, Federal Bulk Pack.
I have not shot it past 50 feet, yet. However, at that range I have been impressed with the accuracy. At 50', my dad put 5 rounds Winchester Xperts into a dime sized group, leaning on the bench. He had never fired an AR before. An older gent (I would say in his late 70's or early 80's) who had also never held or fired an AR before put 5 rounds into a golden dollar sized group at 50' with it- off hand. All with A2 Iron sights.