The FN AR-15 Barrel in 5.56x45mm at 20 inches with a rifle-length gas system (brand part no. 36424) draws on FN’s more than 100-year legacy of barrel manufacturing, hammer forging every barrel from the same proprietary Chrome Moly Vanadium steel used in FN’s machine gun barrels built for sustained automatic fire. Each barrel is Magnetic Particle tested after forging to confirm it is free of micro-stresses, and the bore and chamber are chrome lined to resist corrosion and heat erosion, extending barrel life and improving reliable chambering and extraction. M4-style feed ramps and a matching barrel extension keep feeding consistent, while the matte black Manganese Phosphate finish resists external corrosion. At 20 inches with a rifle-length gas system, it is built for shooters who want maximum velocity and effective range out of a 5.56 AR-15.

Key Specifications

• Chambered in 5.56x45mm NATO.
• Measures 20 inches long with a rifle-length gas system for maximum 5.56 velocity.
• Cut with a 1:7 twist rate.
• Cold hammer forged from proprietary Chrome Moly Vanadium steel.
• Bore and chamber are chrome lined to resist corrosion and heat erosion.
• Every barrel is Magnetic Particle tested after forging to check for micro-stresses.
• Uses M4-style feed ramps with a matching barrel extension for consistent feeding.
• Finished in matte black Manganese Phosphate for corrosion resistance.

Frequently Asked Questions

What gas system length does this barrel use? A rifle-length gas system, matched to its 20-inch length for maximum 5.56 velocity.

Is the bore chrome lined? Yes, both the bore and chamber are chrome lined to resist corrosion and heat erosion.

How is this barrel manufactured? It is cold hammer forged from Chrome Moly Vanadium steel and Magnetic Particle tested after forging.

Buy the FN AR-15 Barrel, 20-Inch Rifle-Length

Stretch the effective range of your 5.56 AR-15 with this FN barrel, part of our full rifle parts and accessories selection. Order it from our Lubbock, Texas gun shop and our team can help confirm fit with your build.