FN Barrel AR-15 Pistol 5.56x45mm 14.7" M4 Contour Carbine Length Gas Port 1 in 7" Twist Chrome Lined Chrome Moly Matte

Building a reliable AR-15 pistol platform starts with a barrel you can trust. The FN Barrel AR-15 Pistol in 5.56x45mm with a 14.7" M4 contour profile gives you a factory-quality foundation backed by FN's military manufacturing standards. Chrome-lined bore and chamber resist corrosion and heat erosion, extending barrel life and keeping your feeding and extraction consistent shot after shot—whether you're running suppressed, doing home defense drills, or training at the range.

FN barrels are button-rifled from U.S.-sourced Chrome Moly Vanadium and hold Mil-B-11595E specifications. Every barrel comes High Pressure Tested (HPT) and Magnetic Particle Inspected (MPI) to catch micro-stresses and flaws before they leave the factory. The M4-style feed ramps and barrel extension ensure reliable chambering and extraction across quality ammo. The matte Manganese Phosphate finish is built to handle hard use—it resists external corrosion and oxidation without the gloss.

The carbine-length gas system and 1:7 twist rate deliver the kind of balanced handling and accuracy that works across typical 5.56 loads. This is a no-nonsense OEM-grade barrel for builders who want a known-good component and don't need to guess about the metallurgy or QC.

Key Features

• Chrome-lined bore and chamber for corrosion resistance and extended barrel life
• Button-rifled from Chrome Moly Vanadium per Mil-B-11595E specifications
• High Pressure Tested (HPT) and Magnetic Particle Inspected (MPI) for consistency and reliability
• M4-style feed ramps and barrel extension for reliable feeding and extraction
• Matte Manganese Phosphate finish resists external corrosion and oxidation
• Carbine-length gas system for balanced performance
• 1:7 twist rate for stable velocities across standard 5.56 ammunition

Specifications

Frequently Asked Questions

What's the difference between a pistol-length and carbine-length barrel on an AR-15?

This FN barrel uses a carbine-length gas system, which is common on mid-length to full-sized AR platforms and provides a good balance of reliability and handling. On a shorter AR pistol receiver, a carbine gas system will cycle reliably with standard 5.56 loads and works well with suppressors.

Why is the bore chrome-lined?

Chrome lining resists corrosion from moisture and the acidic residue of fired cases, and it reduces wear from heat erosion. This extends the usable life of the barrel and helps maintain consistent chambering and extraction over thousands of rounds.

What does HPT and MPI mean?

HPT (High Pressure Test) and MPI (Magnetic Particle Inspection) are quality-control procedures. Every FN barrel is pressure-tested to ensure it handles proof loads safely, and then magnetically inspected to detect any internal flaws or micro-stresses that could cause failure. This process guarantees consistency and reliability.

Is this barrel compatible with standard AR-15 receivers and handguards?

Yes. The FN barrel uses standard M4-style feed ramps and a mil-spec barrel extension, so it will fit any standard AR-15 pistol receiver and work with common drop-in or free-floated handguards designed for M4 barrels.