Review Of Benelli M4 Tactical Shotgun According to the different Benelli M4 Review, this is the 1st gas-controlled shotgun created by Benelli. The shotgun is designed to function on ARGO (Auto Regulating Gas Operating) system and is a totally innovative technique of gas regulation. It has double stainless steel pistons that can be self-cleaned and is positioned just in front of the cavity and function directly aligned with the assembly of bolts. The M4 comprises of the normal Picatinny bar for optics, a phantomring entirely variable back view plus a permanent cutting edge front view.