The Stern Defense Complete Upper is a high-performance 45 ACP assembly designed for the AR-Platform. It features a 16.10 4150 Chrome Moly Steel barrel with a black Melonite finish and a 1:16 twist rate. Built on a forged 7075-T6 aluminum receiver with a black anodized finish, this unit includes a 15 M-LOK free-float rail and a pre-installed SD CB45 compensator brake with a .578x28 thread pattern. This complete system ships with an enhanced charging handle and a specialized Glock-cut blowback bolt carrier group, providing a reliable plug-and-play solution for pistol caliber carbine builds. Note: The blowback-operated bolt carrier group is specifically machined with a Glock-cut profile to ensure reliable feeding and cycling when used with Glock-style 45 ACP magazines.