The Ruger® AR-556® Semi-Auto Rifle operates with a traditional, direct-impingement system. A 6-position MOE SL buttstock allows rapid adjustment according to the clothing and tactical gear the user wears, or for moving from open environments to tight quarters. The standard tactical handguard is made from heat-resistant, glass-filled nylon. The medium contour cold hammer-forged barrel has a 1:8'' twist rate that stabilizes bullets from 35 to 77 grains. A Ruger flash suppressor is attached to the barrel with a 1/2''-28 thread. The barrel nut and delta ring are designed for 1-person removal and installation of most standard carbine length handguards. The anodized flattop upper receiver is made from aerospace-grade 7075-T6 aluminum, and includes a forward assist, dust cover, and brass deflector. The Ruger AR-556 Semi-Auto Rifle comes with one 30- or 10-round magazine. Operates with 5.56 NATO or .223 Remington ammunition.