Ballistic Advantage BABL556015M Modern Series 223 Remington/5.56 NATO Gauge 16" QPQ Corrosion Resistant Rifle This Ballistic Advantage Government Profile Mid-Length Modern Series Barrel is machined from 4150 Chrome Moly Vanadium steel with a QPQ corrosion resistant finish and QPQ coated M4 feed ramp extension. Caliber or Gauge: 223 Remington/5.56 NATO