We have 12 M4 style uppers in stock ranging from $499-$625. These are complete with semi auto bolt carrier groups. The barrels are CMV 1:7 twist with M4 feed ramps.
Bottom (pistol) $899
All of these are $499
ETA: There might be some uppers in our shop that are priced greater than $625. At the time I posted this thread up I didn't realize that we couldn't have items in our shop that weren't listed in this thread.