The FN AR-15 Barrel (brand part no. 20-100046) is a 16-inch, M4-profile replacement barrel chambered in 5.56 NATO/.223 Remington and machined from U.S.-sourced Chrome Moly Vanadium steel to Mil-B-11595E specification. FN button-rifles the bore with a 1-in-7-inch right-hand twist, then High Pressure Tests and Magnetic Particle Inspects every barrel to confirm it’s free of the micro-stresses that shorten barrel life. The bore and chamber are chrome-lined for corrosion resistance and heat erosion protection, M4-style feed ramps and barrel extension keep feeding reliable, and a matte black manganese phosphate finish resists oxidation in the field.

Key Specifications

• Chambered in 5.56 NATO/.223 Remington.
• Measures 16 inches in barrel length.
• Rifled with a 1-in-7-inch right-hand twist.
• Button-rifled from U.S.-sourced Chrome Moly Vanadium steel meeting Mil-B-11595E.
• High Pressure Tested (HPT) for structural integrity.
• Magnetic Particle Inspected (MPI) to catch micro-stresses and flaws.
• Bore and chamber are chrome-lined for corrosion and heat resistance.
• Features M4-style feed ramps and barrel extension for reliable feeding.
• Finished in matte black manganese phosphate for corrosion resistance.

Frequently Asked Questions

Is this barrel HPT and MPI tested? Yes, every barrel is High Pressure Tested and Magnetic Particle Inspected.

Is the bore chrome-lined? Yes, both the bore and chamber are chrome-lined for corrosion resistance.

What twist rate does this barrel use? A 1-in-7-inch right-hand twist.

Buy the FN AR-15 Barrel

Build a mil-spec-tested carbine upper with a chrome-lined, HPT/MPI-verified FN barrel. Order it from our FN America / FN Herstal lineup of AR barrels for fast shipping from our Lubbock, Texas gun shop.