The LUXUS ARMS (HM Defense) MonoBloc Upper (brand part number 16MBUP556) is built around an HM Defense barrel with an integral, machined-in gas block, chambered in .223 Remington/5.56 NATO with a 16-inch length and Black Cerakote finish. The 4150 chromoly barrel is match grade, triple honed, and button rifled with a 1:8 twist, and the free-floating 15-inch M-LOK handguard combines a Picatinny top rail with a 6061-T6 aluminum body. Both the upper and lower receiver areas of this LUXUS ARMS (HM DEFENSE) build are 7075-T6 aluminum with a hard coat anodized finish, and the upper ships with HM Defense’s patented HMB bolt, mil-spec components, a charging handle, and a dust cover featuring an American flag design.

Key Specifications

• Barrel length is 16 inches, chambered in .223 Remington/5.56 NATO.
• Twist rate is 1:8, with a 4150 chromoly, match-grade, button-rifled barrel.
• Finished in Black Cerakote for durability.
• Features an integral, patent-machined gas block built into the barrel.
• Handguard is a free-floating 15-inch M-LOK design in 6061-T6 aluminum.
• Upper receiver is 7075-T6 aluminum, hard coat anodized.
• Includes HM Defense’s patented HMB bolt and a charging handle.
• Sights are optic-ready, with no fixed iron sights included.
• Runs a carbine-length gas system.

Frequently Asked Questions

What makes the MonoBloc gas block different? It is machined as one integral piece with the barrel rather than a separate clamp-on gas block, reducing potential points of failure.

Does this upper include a dust cover? Yes, it ships with a dust cover featuring an American flag design.

Buy the HM Defense MonoBloc 16-inch Upper

Add a durable, integral-gas-block upper to your next AR-15 build. Order this AR-15 upper from our Lubbock, Texas gun shop for fast, insured shipping to your door.