AIM Sports Inc Complete AR 16in .300 Blk Pistol Length Gas System Upper w/Nitride BCG Black Large Black Large. 300 Blackout complete rifle upper receiver assembly is the perfect addition for your complete lower receiver assembly. The upper features a factory installed 16" 4150 CMV barrel with nitride finish. The upper receiver features fully installed forward assist and dust cover. Specifications for AIM Sports Inc Complete AR-15 .300 Blk 16in Upper w/Nitride BCG: Manufacturer: AIM Sports Inc Caliber: .300 AAC Blackout Barrel Length: 16 in Color: Black Features of AIM Sports Inc Complete AR-15 .300 Blk 16in Upper w/Nitride BCG 16" Barrel 4150 Chrome Moly Vanadium Steel A2 muzzle brake and crush washer Mid length gas tube and low profile gas block Mil-Spec Forged 7075-T6 complete Upper with dust cover and forward assist Bolt Carrier Group 8620 steel and bolt is 9310 tool steel with a Nitride finish Package Contents: AIM Sports Inc Complete AR-15 .300 Blk 16in Upper w/Nitride BCG AIM Sports Inc AR5CUB10: Complete AR 16in .300 Blk Pistol Length Gas System Upper w/Nitride BCG Black Large AR5CUB10 Black Large