The Benelli M4 is a semi-automatic shotgun produced by Italian firearm manufacturer Benelli Armi SpA, and one of Benelli's "Super 90" series of semi-auto shotguns. The M4 uses a proprietary action design called the "auto-regulating gas-operated" system, which was created specifically for the weapon. The Benelli M4 Tactical Shotgun has been battle-proven for reliability around the world by the U.S. Marine Corps since 1998. The Benelli M4 semi-auto shotgun operates by a unique, Auto-Regulating Gas-Operated (A.R.G.O.) system, featuring dual stainless steel, self-cleaning, pistons that bear directly on the bolt assembly. Benelli's ARGO mechanism eliminates the more complicated linkages and heavier parts of other semi-auto shotgun designs, to produce a relatively simple and robust action.