Barrett Model 82A2 semi-automatic rifle. .50 Caliber
The Barrett Model 82A2 semi-automatic rifle is slightly smaller and lighter than previous Barrett models but has essentially the same mechanism. By relocating the pistol grip and trigger unit it has been converted to a bullpup configuration, with the shoulder rest behind the magazine, allowing much of the receiver to pass across the firer's shoulder. This makes the weapon more handy and also reduces concealment problems.
Picture and Information from: PIERANGELO TENDAS