The Benelli M4 Super 90 is an Italian semi-automatic shotgun manufactured by Benelli Armi SpA. The M4 was the first gas-operated shotgun produced by Benelli. Its function is designed around an entirely new method called the "auto regulating gas operated" (ARGO) system. The short-stroke design uses two stainless-steel self-cleaning pistons located just ahead of the chamber to function opposite the rotating bolt, thereby eliminating the need for the complex mechanisms found on other gas-actuated automatics. The ARGO incorporates only four parts: two symmetrical shrouds containing two small steel gas pistons.