<p>The Ruger&reg; AR-556&reg; MPR Semi-Auto Rifle operates with a direct-impingement and rifle-length gas system. The lower receiver comes equipped with a Magpul&reg; MOE&reg; pistol grip and a MOE SL&trade; 6-position, collapsible buttstock on a mil-spec buffer tube. Upper and lower receivers are CNC-machined from 7075-T6 aluminum forgings and Type-III hard-coat anodized for maximum durability. A 15&quot; free-float, M-LOK&reg; handguard features accessory attachment slots at 3:00, 6:00, and 9:00 positions, and a continuous Picatinny rail interface with the flat-top, railed, upper receiver. The upper receiver features a forward assist, dust cover, and brass deflector. A Ruger&reg; Elite 452&reg; 2-stage, AR-Trigger offers a smooth, crisp break at approximately 4.5 lbs. The bolt carrier and gas key have chrome-plated inside diameters to provide exceptional resistance to hot gases; and the gas key is securely staked to prevent loosening during extensive fire. The cold hammer-forged 4140 chrome-moly steel barrel comes with an M4 feed ramp and black nitride finish. A 1:8&quot; rate-of-twist rifling maximizes accuracy with bullets ranging from 35 to 77 grains. A Ruger radial-port flash suppressor is attached to the barrel with a 1/2&quot;x28 thread. The Ruger AR-556 MPR Semi-Auto Rifle comes with a 30-round Magpul&reg; PMAG&reg; detachable box magazine.&nbsp;</p> <ul> <li>Direct-impingement system</li> <li>Rifle-length gas system</li> <li>Free-float, M-LOK handguard</li> <li>MOE SL 6-position buttstock</li> <li>MOE pistol grip</li> <li>Ruger Elite 452 trigger</li> <li>Black nitride-finished barrel</li> <li>Radial-port flash suppressor</li> <li>Forward assist and dust cover</li> <li>Flattop upper receiver</li> <li>1:8&quot; rate-of-twist rifling</li> <li>30-round PMAG detachable box magazine</li> </ul>