The FN AR-15 Barrel (brand part no. 20-100043) is a 20-inch, button-rifled replacement barrel chambered in 5.56 NATO/.223 Remington with a 1-in-7-inch right-hand twist built around a rifle-length gas system. FN machines the barrel to a government profile with M4 feed ramps, giving builders the same contour and feeding geometry found on mil-spec rifle-length uppers. The matte black finish resists wear, and the threaded muzzle keeps a muzzle device or suppressor on the table. It’s a factory-spec option for building or restoring a full-length AR-15 rifle upper.

Key Specifications

• Chambered in 5.56 NATO/.223 Remington for standard AR-15 ammunition.
• Measures 20 inches in barrel length.
• Rifled with a 1-in-7-inch right-hand twist.
• Button-rifled construction for consistent accuracy.
• Built around a rifle-length gas system.
• Machined to a government profile contour.
• Features M4 feed ramps for reliable feeding.
• Finished in matte black for wear resistance.
• Threaded at the muzzle for muzzle devices or a suppressor.
• Ships without sights, so it mounts cleanly to your upper’s sighting setup.

Frequently Asked Questions

Is this barrel threaded at the muzzle? Yes, it is threaded for a muzzle device or suppressor.

What gas system length does it use? A rifle-length gas system.

What is the barrel’s twist rate? A 1-in-7-inch right-hand twist.

Buy the FN AR-15 Barrel

Build or restore a full-length rifle upper with a factory-spec FN barrel. Order it from our FN America / FN Herstal lineup of AR barrels as soon as it’s ready to ship from our Lubbock, Texas gun shop.