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Chrome-Lined HM MONOBLOC Barrel – Lead & Steel Exclusive, Various lengths

5.00 out of 5
(11 customer reviews)




The HM Monobloc barrel includes an integrally machined & patented gas block. Chambered in 5.56 NATO/223 Rem, the 4150 Chromoly Vanadium barrel comes in various lengths. This barrel features a 1:8 twist ratio and a mid-length gas system, with a manganese phosphate coated exterior, chrome lined bore, and match crown for maximum service life, EXCLUSIVE to Lead & Steel!

All HM Defense barrels are match-grade, tripled-honed & button-rifled for superior accuracy. All barrels feature Mil-spec M4 feed ramp extensions, properly installed & head spaced.


  • Gas block integrally machined as part of barrel.
  • Eliminates gas block installation & alignment.
  • Improved barrel harmonics for better accuracy.
  • Dependable performance in severe conditions.
  • Low profile; clears barrel nut & allows rail swap, if pinning & welding muzzle device.
  • Chrome lining, lightweight tapering, & target crowning EXCLUSIVE to Lead & Steel!

Barrel Weights:

  • 12.5″ Barrel: 26.2oz
  • 13.9″ Barrel: 26.0oz
  • 14.5″ Barrel: 26.7oz
  • 16″ Barrel: 30.7oz

Ahmad’s take:

Guys, these barrels are unreal. Traditional barrels are turned & relatively easy to manufacture. These require special CNCs; HM starts with a 4150 blank & turns it down until a barrel + gas block is formed.

No more gas loss/leak, dimpling, screwing, drilling, pinning, thermal expansion/shift, etc. This is the most bombproof gas block setup in the industry. Because there’s no gas loss, we can get away with a more conservative port size.

These barrels have low recoil & take very well to a suppressor. Medium contour, & best of all, world-class, sub-MOA accuracy. They can group. You won’t be disappointed.

Read more about HM Defense’s MonoBloc technology, from the Lead & Steel resource center, here.


Additional information

Weight N/A
Select Length

12.5" Manganese-phosphate Exterior – CHROME-LINED, 13.9" Manganese-phosphate Exterior – CHROME-LINED, 14.5" Manganese-phosphate Exterior – CHROME-LINED, 16" Manganese-phosphate Exterior – CHROME-LINED

11 reviews for Chrome-Lined HM MONOBLOC Barrel – Lead & Steel Exclusive, Various lengths

  1. 5 out of 5

    Grant R (verified owner)

    Super Epic.

  2. 5 out of 5

    D Diggler (verified owner)

    Nice people and fast shipping, what else is there

  3. 5 out of 5

    David E.

    Glad to see you can now get the barrels stand alone. I obtained one of the first Monoblocs HM produced a few years ago. It is, quite simply, the best AR barrel I have ever owned. The Monobloc eliminates common issues with the gas port and for some reason – I don’t know why – it is stupendous with suppressors and full-auto. Extremely well designed and a surprising improvement for a platform that has been around for 60 or so years. I paired it with the HM Bolt and feel like I have the best AR rig rocking. If you could afford the Monobloc with HM’s “integral” suppressed barrel, I would consider that the ultimate kit.

  4. 5 out of 5


    Great barrel!
    20″ version is definitely needed.

  5. 5 out of 5

    Chris B. (verified owner)

    Very quick shipping. Looks like a high quality barrel. I have not installed on rifle yet, so no comment on accuracy.

  6. 5 out of 5

    timothy (verified owner)

    A bullet proof setup for ever the shtf!! It’s my second barrel/build and it is worth the $!

  7. 5 out of 5


    Will you ever consider offering a Monobloc barrel in 11.5″ length? That is something me and several thousand other people are interested in. Or maybe even 10.5″. Thanks.

  8. 5 out of 5

    Kane (verified owner)

    The customer service and communication was above and beyond. Mine took awhile to ship but these guys kept me informed as to what was going on. As a “durability fanatic” I’m very pleased with this barrel.

  9. 5 out of 5


    Barrel os nice. Definitely seems bomb proof. However, it is an hbar/socom profile. So its HEAVY! I wish they made some more modern profiles that would trim some weight. Overall a great barrel for heavy firing schedules.

  10. 5 out of 5

    Austin (verified owner)

  11. 5 out of 5

    Patrick (verified owner)

    Used a 13.9” for quasi block ll build. Nothing but good things to say about it, will be getting another for my next build.

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