Ruger AR-556 Semi-automatic 5.56 NATO Centerfire Rifle. The Ruger AR-556 is a semi-automatic M4-style, direct impingement Modern Sporting Rifle that offers consumers a fun to shoot, affordable rifle with rugged reliability. Extensively tested during its development, the AR-556 is constructed from top-quality components, including forged 7075-T6 aluminum upper and lower receivers and a cold hammer-forged, chrome-moly steel barrel with M4 feed ramp cuts. This model is chambered in 5.56 NATO and comes equipped with a telescoping 6-position stock, 30-round Magpul magazine and enlarged trigger guard. Plus, it uses standardized M4 / AR components so customization is hassle free. Chambered for both 5.56 NATO (also called 5.56x45mm) and .223 Remington Forged 7075-T6 aluminum upper (type III hard-coat anodized) with forward assist, dust cover and brass deflector Forged 7075-T6 aluminum lower with Type III hard-coat anodized finish Heat-resistant nylon handguard for shooting comfort Milled gas block is located at carbine length position for improved balance and handling Ergonomic pistol grip features an extended trigger reach for more precise trigger control Barrel nut and delta ring are designed for 1-person handguard removal and installation Shot peened, 9310 alloy steel bolt Multiple attachment points include a QD socket and bayonet lug, for many sling and accessory mounting options Barrel is threaded (1/2 inch-28) Includes 30-rd. Magpul PMAG magazine