The Sig 556 features the same high performance two position adjustable gaspiston operating rod system engineered by Sigs sister company Swiss Armsand marries it to a trigger housing that not only cuts the rifles weight bya pound but is designed to accept standard AR magazines. The Picatinny railequipped receiver is made of high strength carbon steel with a durable wearresistant Nitron X rifle finish. The rifle comes equipped with a smooth twostage trigger. A 30 round magazine is supplied with each rifle. SPECIFICATIONS:Mfg Item Num: R55616BCSRD Action :Semi-AutomaticCaliber :223 Remington/5.56 NATOBarrel Length :17"Capacity :30+1Trigger :Two StageSafety :AmbidextrousOAL :37.8"Weight :8.3 lbsStock :FoldingFinish :Black