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LS ARC Build Barrels


$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

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