HM Defense MONOBLOC 16 Inch Complete 5.56 AR-15 Upper Receiver with 15 Inch M-LOK Handguard

SKU: 16MBUP-556-L

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Cost-Effective Complete Upper Receiver for A High-Performance AR-15 Build

This HM Defense BUP Complete Upper Receiver features a 16-inch 4150 Chromoly barrel with a patented integrally machined gas block, and a carbine gas system. HM defense has developed a revolutionary gas block that is actually part of the barrel, which greatly improves the barrel harmonics for better accuracy and provides a dependable performance even in severe conditions.

Included in this complete upper is the HM Defense 15-inch Free Float Picatinny Rail Handguard machined from 6061-T6 aircraft-grade aluminum. Also included is a patented HMB bolt, a charging handle, and a dust cover with an American Flag.

This upper receiver represents a high-quality option that will allow you to complete your next AR-15 for a top-performance build.


  • Barrel: The HM MONOBLOC upper includes an integrally machined patented gas block. Chambered in 5.56 NATO/223 Rem, the 4150 Chromoly barrel is 16 inches in length and features a 1:8 twist ratio and a mid-length gas system. All HM Defense barrels are match grade, tripled honed, and button rifled for superior accuracy.
  • Handguard: The custom HM Defense 15 inch, free float 1913 Picatinny rail is CNC machined from 6061-T6 aircraft grade aluminum. The rail is compatible with Magpul M-LOK mounting system.
  • Upper Receiver: HM Monobloc upper features a Mil-Spec Forged 7075- T6 M4 Upper Receiver with Type III Class II hard-coat black anodized finish, M4 Feed Ramps, and a 1913 Picatinny rail flattop.
  • Components: HM Defense Monobloc upper includes an M16 bolt carrier group with patented HMB bolt and Mil-Spec components and charging handle. Includes dust cover engraved with an American flag.
  • Muzzle Brake: HM Defense Monobloc upper includes CNC machined muzzle brake.
  • Barrel Finish: Rifle Black Cerakote finish.


  • Type: Complete Upper Assembly
  • Barrel Length: 16″
  • Caliber: 223 Remington
  • Caliber: .223/5.56 NATO
  • Color: Black
  • Handguard: 15″ M-LOK Rail
  • Finish: Anodized
  • Fit: AR15
  • Subcategory: Complete Upper Receivers
  • Type of Barrel: 1:8

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