.50, M107. The M107 uses a Leupold 4.5–14×50 Mark 4 scope. The Barrett M107 is a .50 caliber, shoulder-fired, semi-automatic sniper rifle. Like its predecessors, the rifle is said to have manageable recoil for a weapon of its size owing to the barrel assembly that itself absorbs force, moving inward toward the receiver against large springs with every shot. Additionally, the weapon's weight and large muzzle brake also assist in recoil reduction. Various changes were made to the original M82A1 to create the M107, with new features such as a lengthened accessory rail, rear grip, and monopod socket. Barrett has recently been asked to develop a lightweight version of the M107 under the Anti-Materiel Sniper Rifle Congressional Program and has already come up with a scheme to build important component parts such as the receiver frame and muzzle brake out of lighter-weight materials. The Barrett M107, like previous members of the M82 line, is also referred to as the Barrett "Light Fifty". The designation has in many instances supplanted earlier ones, with the M107 being voted one of 2005's top 10 military inventions by the U.S. Army. The U.S. Army and Marine Corps plan to field another Barrett rifle, the Mk22 MRAD, in 2021 to replace the M107. The Mk22 is a bolt-action multi-caliber rifle that is powerful enough to replace the M107 when chambered in .338 Norma Magnum. Technical description The M82 is a short-recoil semi-automatic firearm. When the gun is fired, the barrel initially recoils for a short distance (about ), while being securely locked by the rotating bolt. After the short travel, the lower part of the accelerator arm, held by the receiver upper part, is already hinged in the bolt carrier and the middle portion strikes it back to the barrel by a rod placed in the bolt carrier, transferring part of the recoil energy of the barrel to the bolt to achieve reliable cycling and unlock it from the barrel. The bolt is unlocked by turning in the curved cam track in the bolt carrier. Then the barrel is stopped by the combined effect of the accelerator, buffer spring, and the muzzle brake and the bolt continues back, to extract and eject a spent case. On its return stroke, the bolt strips the fresh cartridge from the box magazine and feeds it into the chamber and finally locks itself to the barrel. The striker is