Monobloc Barreled Rifles from HM Defense

HM Defense & Technology manufactures AR-15 barrels that have an integrated gas block rather than a separate block that mounts onto the barrel. Now the company is shipping complete AR-15 rifles that use these barrels.

According to the company, the Monobloc barrel offers advantages over the traditional gas block system. These benefits include:

  • no gas hole alignment issues – a potential failure point
  • no issues with different heat expansion rates that can affect gas hole alignment and gas block rupturing
  • no problems with increased back pressure from suppressed weapons


The new Monobloc rifles are AR pattern guns designated HM15-MB-556. The guns use machined lowers and a 16″ Monobloc barrel. Additional specs on the guns include:

  • type III hardcoat anodizing
  • 12″ HM Defense hand guard with a Picatiny rail on top and M-LOK on the sides
  • quick change gas tube system
  • machined V1-556 flash hider
  • Magpul MOE pistol grip, adjustable length stock and 30-round magazine
  • HM Defense end plate with DQ attachment

The guns do not ship with sights. However, the Picatinny rail allows for the addition of a wide range of iron and glass sighting options.

The suggested retail price of the new rifle is $1,495. The rifles come with a five year warranty and a t-shirt with the company’s logo.

Richard Johnson

An advocate of gun proliferation zones, Richard is a long time shooter, former cop and internet entrepreneur. Among the many places he calls home is


  • James

    Interesting! How about gas tube alignment?

    • bull

      since you got that alignment thing on the barrel extension/trunnion thing the alignment should be spot on.

  • thei3ug

    How does this prevent increased back pressure?

    • SF

      it doesn’t, and it doesn’t say it does

  • thedonn007

    So, the gas tube must be able to slide through the gas block to allow for installation of the barrel on the upper receiver. It is a neat idea, but I would not want to give up the ability to add an adjustable gas block, or a pistion system if that is what you desire.

    • DIR911911 .

      why? when that means two MORE guns yeah!!

  • Edeco

    Interesting: as a puritanical lunatic I’m all about eliminating a joint/seperate part. Still, a barrel is basically cylindrical in nature, having an appendage must complicate manufacture, so I have my reservations.

    • micmac80

      Its no big deal just a larger cylinder machined away like for example pistol barrels.

      • Edeco

        Yeah. I mean, I don’t know how the billet for barrels is made… I assume some kind of rolling and/or drawing. Can a larger diameter piece have the grain controlled as nicely? Even if smaller diameters can be controlled better, is anyone bothering to do so? I do not know. I could be making a mountain out of a molehill.

    • Vhyrus

      A live tooling CNC lathe would knock these bad boys out in no time flat. Definitely not a do it yourself level project but way inside traditional commercial manufacturing processes. Overall I think this is a significant improvement over current mounted gas blocks assuming the price is reasonable. I am curious how the gas port is drilled. I assume that’s the reason there’s an extra hole in the top of the gas block section in the above picture.

  • TF82

    So…. how do they get the barrel nut on there?

    • Dr. Longfellow Buchenrad

      Exactly the question I have

    • Nobody Inparticular

      it looks like the block is small enough for the barrel nut to go over it.

    • DIR911911 .

      if you look you’ll notice the chamber area that the barrel nut has to go around is larger than the gas block area , therefore no problem.

  • Austin

    That’s weird, I could have sworn that back pressure from suppressors was caused by the suppressor itself, not by whether or not your gas block was a seperate component from your barrel. Huh, learn something new every day. Now BRB, gotta go TIG up all my gas blocks to magically eliminate back pressure.

    • SF

      it doesn’t say there is not increase in back pressure, just that the problems of increased back pressure is eliminated, implying that the problems with gas blocks getting destroyed from increases in back pressure is eliminated. of course you still have to worry about the bolt carrier and whatnot

    • SF

      reading is FUNdamental

    • josh

      better bone up on your reading comprehension, it was never said that the gas block creates the increased back pressure. They are talking about the increase in back pressure causing problems with the gas blocks.

  • Gorilla Biscuit

    A gas trap system might be even more better????

    • mig1nc

      Armstech? I always wanted to try one.

  • Richard

    $1,495 and no sights? I know it’s Nitpicky but you’d think that they would throw in some sights for that price.

  • therealgreenplease

    One less part to fail so that’s a plus. I’ve actually seen two rifles “fail” because their gas blocks moved forward on the barrel thus blocking off the flow of gas. Granted these were gas blocks held on with a set screw. A gas block held on with taper pins should virtually never fail but I’m always a fan of fewer parts.

  • mig1nc

    Wonder if they will make one with adjustable gas? Or maybe the adjustable bolt carriers on the market now make that a moot question?