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

4.83 out of 5
(12 reviews)

$499.99 $349.99

$499.99 $349.99

In Stock



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.


Additional information.

  • Weight

  • 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


4.83 out of 5
(12 reviews)

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

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  1. 3 out of 5

    Niko (verified owner)

    Mine just doesn’t want to group, I really wanted to like the barrel and I figured if I kept shooting maybe it would eventually break in and start being more accurate but just hasn’t happened for me. 2-3 moa at 50 yards if I do my part! Once in a while I’ll get that 1inch at 50. Bummer because I had all the work done before testing its accuracy. P/w a surefire and had it converted to fit Lmt receivers. It was an expensive project for a “bomb proof” build I was shooting for.

  2. 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.

  3. 5 out of 5

    Austin (verified owner)

  4. 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.

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