The PWS MK1 MOD 1-M Complete Upper Receiver features the renowned PWS Long Stroke Piston System in 7.62x39mm with a 16.1-inch barrel for reliable high-performance operation.PWS MK1 MOD 1-M Complete Upper ReceiverCaliber: 7.62x39mm with 16.1" barrelPWS Long Stroke Piston System with 3-setting adjustable gas regulatorT6 7075 forged and anodized upper receiverFree-float M-LOK 15.05" handguard1:8 barrel twist rate 2980fps muzzle velocityRadian Raptor ambidextrous charging handlePWS FSC 556 muzzle deviceMid-length gas systemDesigned for both civilian and law enforcement use this mil-spec upper receiver delivers exceptional reliability and performance for demanding applications where dependability is critical.