MPN: 16MB-556


  • Built-in gas block, eliminating the need for a traditional gas block - means gas block will never be a failure point
  • Eliminated gas hole alignment issues
  • Eliminated the issue with different heat expansion rates that can affect gas hole alignment and gas block rupturing
  • Eliminated gas block failure with increased back pressure from suppressed weapons
  • Low profile gas system will compatible with all standard barrel nut - gas block only protruding 0.280" above the barrel
  • Comes with gas tube and gas block roll pin


  • Caliber: 5.56 NATO / .223 Rem
  • Twist Rate: 1:8 Twist
  • Material: 4150 CrMo Steel
  • M4 Feed Ramps: Yes
  • Muzzle Thread Pattern: 1/2"-28 TPI
  • Outside Finish: Cerakote
  • Gas Placement: Mid-Length
  • Gas Hole: 0.081
  • Weight: 2 lbs 1 oz.


  • AR-15 upper receiver


Have you ever lost a day at the range due to a gas block failure on your AR-15? Now the future of tactical barrels is here with the creation of the HM Defense Monobloc Barrel. State of the art machining gives you a complete, match grade barrel to fill your needs. You will save time and labor with the easy installation of this monobloc barrel. One-piece design eliminates potential weak points on the gas block while delivering Olympic performance.

HM Defense Barrel With Integral Gas Block

The gas block and barrel are machined from a solid steel blank so you never have to worry about critical gas hole alignment. Back pressure can be a constant concern caused primarily by gas block misalignment. On standard barrels, the gas block is attached with a set screw which might shift when installed incorrectly and build fatal back pressure especially when firing a suppressed weapon. Now you can have the HM Defense Monobloc Barrel. Its’ rugged one-piece design eliminates these problems for good.

Free Floating Barrel

Your monobloc barrel is expertly designed to be dependable in severe conditions for a lifetime of shooting pleasure. Machined from one piece of high-grade steel and mounted directly to your upper gives you the benefit of a true free floating barrel. Your barrel will be free of interference to work for you without fail year after year. The HM Defense Monobloc Barrel simply looks like it belongs on your weapon. The spartan design gives way to grace when you let this barrel lead your weapon for you.

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