CORE15 Mil-Spec Forged 7075-T6 M-4 Upper and Lower Receiver Type III Class II Hard-coat anodized finish M4 feed ramps (1913 Picatinny rail flat top) w/ dry lube internal finish and laser engraved T-markings. 16 4150 Chrome Moly M4 profile Chrome Lined Barrel 1:9 Twist Chambered in .223/5.56 x 45 mm NATO Direct Gas Impingement Gas System. - Action: Semi-Automatic - Caliber: 223 Remington/5.56 NATO - Barrel Length: 16 - Capacity: 30+1 - Safety: Lever - Trigger: Standard - Stock: Black 6-Position Collapsible - Finish: Black - Weight: 5.2 lbs