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 12.7x42 upper starts with an AR-15 BIG BORE MILSPEC 7075 T6 Forged Aluminum receiver, mated to a BCA 10.5 inch 12.7x42 (50 Beowulf), Pistol Length Gas System, 1:20 Twist, Heavy Profile, Parkerized Barrel. The Axis 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 and Charging Handle is OPTIONAL. We offer a 12.7 BCG, M16 Profile, Properly Staked Gas Key, MP Tested, 8620 Carrier, 9310 Bolt, Nitride Treated and a Standard Charging Handle. Also an OPTION is COLOR. We can change the receiver and handguard to FDE (FLAT DARK EARTH) COLOR (see pictures). NOTE: We recommend E-LANDER 50 Beowulf Magazines for this caliber. SPECIFICATIONS UPPER RECEIVER: AR-15 BIG BORE Mil-Spec Machined out of 7075-T6 Forged Aluminum, Single Large Feed Ramp, Type III Hardcoat Anodized Black with Forward Assist and Ejection Port Cover Installed BARREL: 10.5 inch, 12.7x42 (50 Beowulf) Caliber, 4150 Chrome Moly Vanadium Steel, 1:20 Twist, Heavy Profile, Parkerized - made by BCA HANDGUARD: 9 inch M-LOK Free Floated, Machined out of 6061 T6 Aluminum - made by Axis MFG GAS SYSTEM: Pistol Length, Direct Impingement, Stainless Steel Tube GAS BLOCK: Low Profile Gas Block, Machined out of 4140 Steel MUZZLE DEVICE: Competition Muzzle Brake Black (49/64-20) with Crush Washer 100% MADE IN THE USA OPTIONAL: ADD a 12.7x42 M16 Profile Nitride BCG and a Standard Charging Handle OPTIONAL: COLOR Change to an Aero Precision XL FDE Colored Receiver and 10 inch M-LOK Magpul FDE Colored Handguard