Cobalt Kinetics CK-Pro URG 5.56 NATO 7.5" FDE Upper Receiver Group

The CK-Pro URG is a complete upper receiver group, so it pins onto any standard AR-15 lower in about ten seconds. This one is set up in 5.56 NATO with a 7.5" barrel under a 6.75" free float M-LOK rail, which is about as short as the platform gets before it stops being practical. Built configuration means the barrel, bolt carrier group and charging handle are all included and assembled by Cobalt's gunsmiths.

The FDE Cerakote is applied over aluminum, and Cobalt's machining is the reason people buy these instead of a generic parts kit. Pair it with a braced pistol lower for a compact 5.56 build.