I purchased one of their national match dcm uppers last year, to replace the shot out barrel on my pre ban colt blue label
fit and finish are excellent, finish is on the darker side as compaired to colt light grey
on the match uppers the nm chanbers are on the tight side (the way they should be) if your brass is not trimmed to spec there can be some problems.
but assuming your ammo is within spec there will be no problems.
As far as accuracy goes im sure the gun is more than capable of making better groups than i can muster
The first 5 rounds i put through it were within half an inch,
At 100 yards shooting in the prone position. using 69 grain siera match kings using iron sights.
Ive never put factory ammo through it only reloads. their customer service is excellent too
IMO I whole heartedly recomend RRA