All our uppers are carefully assembled and tested and ready to go out of the box. Every component is chosen to ensure a high quality upper is produced. Every upper is custom built to order and we go the extra mile to ensure the finished product is to your specifications. This 300 Blackout upper starts with a Gibbz Arms LEFT HANDED G4 Non Reciprocating Side Charging Billet Aluminum receiver, mated to a Ballistic Advantage 6 inch 300 Blackout, Pistol Length Gas System, 1:7 Twist, Govt Profile, QPQ Nitride/Melonite treated barrel. The Gibbz Arms receiver is a proprietary patented receiver that has a non reciprocating side charging handle - handle stays forward during cycling. Side handle is on the opposite side of ejection port allowing the shooter to quickly charge or recharge the weapon without taking finger off the trigger and eye off the scope. Ballistic Advantage is one of the best AR barrel manufacturers in the industry and they produce high quality, accurate barrels. The Bowden Rail is a free floated system, M-LOK slots on all three sides, full length picatinny rail at the top, lightweight handguard. Barrel Nut is made out of solid steel to ensure a solid mounting system. Bolt Carrier Group is OPTIONAL. We offer our very own LEFT HANDED BCG, M16 Profile, Properly Staked Gas Key, MP Tested, 8620 Carrier, 9310 Bolt, Nitride Treated. Made for us by one of the largest BCG manufacturers in the industry. We also offer a CHOICE of Muzzle Devices - upgrade the flash hider to a Black or Stainless Competition Muzzle Brake. This is an enhanced version of the popular style muzzle brakes. The baffles and ports are milled larger to drive pressure up and to keep the muzzle down more effectively. We can also UPGRADE the GAS BLOCK to an Adjustable Gas Block. Great option if you are using a suppressor or just want to fine tune your system. SPECIFICATIONS UPPER RECEIVER: Gibbz Arms LEFT HANDED G4 Non Reciprocating Side Charging Billet Aluminum Receiver with Gen 2 Handle, M4 Feed Ramps, Type III Hardcoat Anodized Black (Gibbz Cam Pin Included) BARREL: 6 inch, 300 Blackout Caliber, 4150 Chrome Moly Vanadium Steel, 1:7 Twist, Govt Profile, QPQ Nitride/Melonite Treated - made by Ballistic Advantage HANDGUARD: 5 inch M-LOK Free Floated, Machined out of 6061 T6 Aluminum - made by Bowden Tactical GAS SYSTEM: Pistol Length, Direct Impingement, Stainless Steel Tube GAS BLOCK: Low Profile Gas Block, Machined out of 4140 Steel MUZZLE DEVICE: Standard A2 Flash Hider and Crush Washer 100% MADE IN THE USA OPTIONAL: UPGRADE Muzzle Device to a Black or Stainless Competition Muzzle Brake OPTIONAL: ADD a Pro2A LEFT HANDED Nitride M16 Profile BCG OPTIONAL: UPGRADE GAS BLOCK to an Adjustable Gas Block