This assurance c model comes chambered in 5.56 with a 16", cmv barrel (carbine length gas system).Picatinny rail gas block comes perfect height for sights and is attached to a rra car lightweight quad-rail.Action: Semi-AutoCaliber: 5.56x45mm NATOBarrel Length: 16"Capacity: 30+1Trigger: Two-Stage MatchSafety: Safety Selector SwitchOal: 33"Weight: 7 lbsStock Description: Adjustable RRA Operator CARMuzzle: A2 Flash HiderReceiver Material: AluminumSights: Optic ReadyBarrel Description: 16" Chrome Moly SteelTwist: 1:8"Barrel Length Range: 16" to 16.99"Weight Range: 7 lbs to 7.99 lbsHand: RightStock Finish Group: Black