Colt Firearms AR-15 Complete Upper Features The Colt Complete Upper is built around a 10.3 barrel chambered in 5.56 NATO and rated for .223 Remington as well giving shooters flexibility in ammunition choice. The barrel carries a 1:7 twist rate which stabilizes heavier bullet weights commonly used for longer range or barrier blind performance in a carbine length gas system. A Nitride finish on the steel barrel improves corrosion resistance and reduces friction for smoother cycling over time which also simplifies cleaning after extended range sessions. Matte black in color the upper matches factory Colt finishes for a seamless look when installed on an existing lower so the completed rifle reads as a single cohesive build rather than a mix of mismatched parts. Built as a complete receiver assembly rather than a bare upper this kit is ready to install directly onto any AR-15 universal lower without additional parts or fitting. The carbine length gas system keeps the platform reliable across a range of ammunition and running conditions typical of shorter barreled AR builds cycling consistently whether the rifle is running lighter varmint loads or heavier barrier rounds. This configuration is a popular choice for shooters looking to convert a rifle length AR-15 into a shorter more maneuverable pistol or SBR configuration since the shortened barrel trims overall length and swing weight for faster handling in tight spaces. For AR-15 owners who want a factory Colt barrel and upper without building one from individual parts this complete upper offers a straightforward path to a 10.3 configuration backed by Colt s reputation for reliable mil-spec quality AR-15 components. Colt Firearms AR-15 Complete Upper Specifications Manufacturer: Colt Firearms Model: AR-15 Complete Upper Caliber: 5.56 NATO / .223 Rem Barrel Length: 10.3 Barrel Material: Steel Barrel Finish: Nitride Twist Rate: 1:7 Gas System: Carbine Length Receiver Style: Complete Color: Black Available At: GrabAGun