The FN AR-15 Barrel (brand part no. 20100039) is a 16-inch, button-rifled replacement barrel chambered in 5.56 NATO/.223 Remington with a 1:7 twist rate built for carbine-length gas systems. FN manufactures the barrel to a government profile with M4 feed ramps, matching the contour and feeding geometry that mil-spec upper builders expect. The matte black finish resists wear, and a threaded muzzle keeps the door open for a muzzle device or suppressor. It’s a straightforward, factory-spec way to build or repair a reliable carbine-length AR-15 upper.

Key Specifications

• Chambered in 5.56 NATO/.223 Remington for standard AR-15 ammunition.
• Measures 16 inches in barrel length.
• Button-rifled construction for consistent accuracy.
• Built around a carbine-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 carbine-length gas system.

Does this barrel include sights? No, it ships without sights for use with your upper’s existing setup.

Buy the FN AR-15 Barrel

Build or repair a reliable carbine-length upper with a factory-spec FN barrel. Order it from our FN America / FN Herstal lineup of AR barrels for fast shipping from our Lubbock, Texas gun shop.