FN | AR-15 Button Rifled Barrel | 223 Rem | 5.56 NATO | Manganese Phosphate

FN's AR‑15 button‑rifled barrels are cut from U.S.-sourced Chrome Moly Vanadium steel per Mil‑B‑11595E, then High Pressure Tested and Magnetic Particle Inspected -⁠- the same real quality‑control process FN applies to its military‑contract barrels, not a lesser commercial‑grade skip. A chrome‑lined chamber with an M4‑style feed ramp and 1/2x28 threaded muzzle at a 1:7 twist back genuine duty‑grade reliability, with a black manganese phosphate finish for real corrosion resistance. Available across 10.5 to 20‑inch lengths with carbine, mid, or rifle‑length gas systems to match the exact build you're doing.