ACI U55616ML 5.56 NATO 16″ M-LOK Upper Receiver Assembly

Complete your AR-15 build with confidence using the ACI U55616ML 5.56 NATO 16″ M-LOK Upper Receiver Assembly — a ready-to-install upper engineered for reliability, versatility, and consistent performance. Chambered in 5.56 NATO, the 16-inch barrel delivers a well-balanced platform suited for range sessions, home defense, hunting, and competitive shooting alike. The M-LOK handguard keeps your setup lightweight and low-profile while giving you the flexibility to mount optics, lights, vertical grips, and other accessories exactly where you want them. Designed to drop onto any mil-spec AR-15 lower receiver, this upper offers a solid fit and finish right out of the box — whether you’re completing a fresh build, upgrading an existing rifle, or replacing a worn upper assembly. At Deep Roots Rifle Co, we specialize in stocking hard-to-find components so you can get your build done right the first time. Order online for fast shipping nationwide, or visit our gun store in Eustis, Florida, where our knowledgeable staff is ready to help you find the right parts for your specific build. Competitive pricing, expert guidance, and a strong selection of AR-15 components — that’s the Deep Roots difference.