4150 CMV — the same alloy specified by the U.S. Military for M4 and M16 barrels. The higher carbon content (~0.50% vs. ~0.40% in 4140) and vanadium addition give it better wear resistance, tensile strength, and heat tolerance under sustained fire. For a duty or training rifle that will see hard use, 4150 CMV is the right material choice over 4140.

Mid-length gas moves the port farther from the chamber, which lowers the pressure hitting the bolt carrier on each cycle. The result is a softer, more linear recoil impulse, significantly less wear on the bolt, carrier, and buffer over the rifle’s service life, and better suppressor performance. Carbine-length gas on a 16" barrel over-drives the action. Mid-length is the better-engineered choice at this barrel length — and it’s what most quality 16" 5.56 builds run.

The Gunner tapers along the barrel’s length, heavier near the breech where the steel does the most work, lighter toward the muzzle. It’s lighter than a SOCOM (which keeps more mass throughout for heat capacity and sustained-fire rigidity) and stiffer than a Pencil (which removes as much mass as possible for ultralight builds). For most 16" general-purpose or competition rifles, the Gunner is the right call. Go SOCOM if you’re prioritizing high-round-count heat management; go Pencil only if every ounce counts and sustained fire isn’t a priority.

5.56 NATO. The 5.56 chamber has a longer freebore than a .223 Remington chamber, allowing it to safely handle both 5.56 NATO military loads and .223 Remington commercial ammunition. A .223 Rem chamber should not be used with 5.56 NATO ammunition — the pressure spike from the shorter freebore is a real concern. Every Faxon barrel is headspace-verified at the factory with a calibrated 5.56 GO/NO-GO gauge.

1:8 right-hand twist. One full revolution in 8 inches of barrel, 6-groove conventional rifling. The 1:8 rate reliably stabilizes the widest practical range of 5.56 NATO weights — from 55gr FMJ through 69gr and 77gr match bullets — making it the most versatile choice for a general-purpose or training rifle. The military’s 1:7 (Combat Series) is optimized for tracer rounds and M855A1; most civilian and LE builders don’t need it.

.625" low-profile gas block. Compatible with any standard .625" fixed or adjustable low-profile gas block. If you’re running a suppressor, an adjustable gas block lets you tune for backpressure and your specific ammo and suppressor combination. Faxon makes both fixed and adjustable options.

1/2"–28 — the standard thread pitch for 5.56 and .223 muzzle devices and most suppressor mounts. Compatible with the vast majority of flash hiders, brakes, and cans designed for this caliber. Always verify your suppressor’s thread pitch and bore diameter before use.

Yes — inside and out. Salt-bath nitride (Melonite/QPQ) is a ferritic nitrocarburizing process that diffuses nitrogen and carbon into the steel surface simultaneously on the bore interior and barrel exterior. It’s a surface treatment, not a coating or plating, so it produces 60+ HRC surface hardness and excellent corrosion resistance without adding any thickness that would affect the rifled bore geometry. Chrome lining adds material and can alter bore dimensions; nitride does not.

Yes. The 1/2"–28 muzzle thread is compatible with most 5.56 suppressor mounts, and the mid-length gas system handles suppressor backpressure better than a carbine-length setup. For regular suppressor use, pair this barrel with an adjustable gas block to dial in your specific suppressor and ammo combination. Faxon also manufactures suppressors designed to integrate with Faxon uppers and barrels.

Faxon runs a multi-stage inspection process — not a single end-of-line check. Air gauging verifies bore diameter to sub-tenth tolerances after reaming and rifling, confirming the bore is within spec before the barrel moves to the turning station. MahrShaft OD measurement confirms critical external diameters — gas block journal, chamber shoulder, and other turned features — are held to the dimensions on the engineering drawing. A CMM (Coordinate Measuring Machine) verifies the positional accuracy of features like gas port location, extension shoulder geometry, and chamber dimensions in three dimensions rather than just checking a single measurement. Every barrel then undergoes 100% wet magnetic particle inspection (MPI) — wet MPI uses a liquid suspension of fine ferrous particles to detect surface and near-surface cracks, seams, and inclusions with greater sensitivity than dry powder methods. And finally, every barrel is headspace-verified with a 5.56 GO/NO-GO gauge after the extension is installed and torqued. That’s not a sampling approach — it’s every barrel, every time.

Entirely in-house in Greater Cincinnati, Ohio. Faxon Firearms is a family-owned manufacturer founded in 2012, built on the foundation of Faxon Machining — a precision machining operation established in 1978 that has served automotive OEM, aerospace, oil & gas, and defense customers. Every step of barrel production, from raw 4150 CMV bar stock through finished, headspace-verified barrel with extension installed, is performed on Faxon’s own equipment by Faxon’s own team.

Faxon’s Lifetime Guarantee covers manufacturing and material defects for the original purchaser. For full terms, exclusions, and service instructions: https://faxonfirearms.com/warranty-privacy-terms/