Benelli is an Italian firearms manufacturer located in Urbino, Italy and is world famous for producing high quality hunting, military and law enforcement shotguns. Benelli's M4 Tactical shotgun is the civilian verson of the U.S. military’s M1014 Joint Services Combat Shotgun. At the heart of the design is Benelli’s piston driven system. Designed to function with 2 ¾” or 3” shells, the M4's ARGO system (which stands for “Auto Regulated Gas Operated”) employs dual stainless self-cleaning pistons, located just ahead of the chamber, that are impinged by hot gases through dual gas ports. This system is, by nature, cleaner than other gas-operated semi-automatics.