This Colt AR15A4 Semi-Automatic Centerfire Rifle is a throwback to the full size AR-15 which gave birth to the Modern Sporting Rifle. The AR15A4 is defined by it's 20" 1:7 Twist Government Profile Chrome Lined Barrel and A2 Fixed Buttstock. The rifle is topped with a Picatinny Flat Top Upper Receiver with Detachable Carry Handle. The Colt model AR15A4 is chambered for 5.56 NATO cartridges and will allow you to shoot 223 Remington as well.FeaturesAdjustable post front sight for elevationRear sight adjustable for windageDirect gas system