The FN AR-15 14.70-Inch M4 Profile Barrel (brand part no. 20100405) is built using the same proprietary high-grade Chrome Moly Vanadium steel and hammer-forging process FN uses on its venerable machine gun barrels, which are engineered to handle the punishment of sustained fully-automatic fire. Every barrel is Magnetic Particle tested after forging to confirm it’s free of microstresses or flaws, which shows up as consistent quality from barrel to barrel. The bore and chamber are chrome lined to resist corrosion and heat erosion, extending barrel life and keeping chambering and extraction reliable over a long service life. M4-style feed ramps and a matched barrel extension ensure consistent feeding, and the matte black manganese phosphate finish resists external corrosion and oxidation. Set up with a carbine-length gas system, this 14.70-inch barrel is a genuine FN-quality upgrade for a duty or defensive AR-15 build; a 14.70-inch barrel measures over the 16-inch federal rifle minimum only when combined with a permanently attached muzzle device, so confirm your configuration meets NFA barrel-length requirements before final assembly on a shouldered rifle.

Key Specifications

• 14.70-inch barrel length with a carbine-length gas system.
• Built in the classic M4 profile contour.
• Cold hammer-forged from Chrome Moly Vanadium steel.
• Chrome lined bore and chamber for corrosion resistance and extended life.
• Every barrel is Magnetic Particle tested to confirm it’s free of flaws.
• Finished in matte black manganese phosphate for corrosion resistance.
• Cut with M4 feed ramps for reliable feeding.

Frequently Asked Questions

What gas system length does this barrel use? It’s built for a carbine-length gas system based on its 14.70-inch length.

Is this barrel chrome lined? Yes, both the bore and chamber are chrome lined for corrosion resistance and heat erosion protection.

Can this barrel be run at under 16 inches on a rifle-configured lower without extra paperwork? No, a rifle-configured (shouldered) lower needs an overall barrel length of at least 16 inches, typically achieved with a permanently attached muzzle device, to avoid NFA short-barreled rifle classification.

Buy the FN AR-15 14.70-Inch M4 Profile Chrome Lined Barrel

Order it from our Lubbock, Texas gun shop for fast, direct shipping to your door, and drop a genuine FN barrel into your next build.

Shop more from FN America / FN Herstal and browse our full AR barrels selection.