The M82 is a short recoil semi-automatic firearm. When the gun is fired, the barrel initially recoils for a short distance (about an inch/25 mm) being securely locked by the rotating bolt. After the short travel, a post on the bolt engaged in the curved cam track in the receiver turns the bolt to unlock it from the barrel. As soon as the bolt unlocks, the accelerator arm strikes it back, transferring part of the recoil energy of the barrel to the bolt to achieve reliable cycling. Then the barrel is stopped 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 also is cocked on the return stroke of the bolt. The gun is fed from a large detachable box magazine holding up to 10 rounds, although a rare 12 round magazine was developed for use in the first Gulf War.
Very cool!! The M82A1 and M107 have small differences-"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."- http://en.wikipedia.org/wiki/M82_Barrett_rifle