The Benelli M4 is a gas-operated semi-automatic shotgun developed for the US Marine Corps as the M1014 Joint Service Combat Shotgun. Unlike all other Benelli shotguns, the M4 uses an ARGO (Auto-Regulating Gas-Operated) system rather than the Inertia Driven mechanism, selected because it cycles reliably with a wider variety of less-lethal and training loads. The M4 Tactical is the civilian production version. Type: Shotgun Action: Semi-Automatic Caliber: 12 Gauge Capacity: 5 Year introduced: 1998, Italy Weight: 7.8 oz Overall length: 40" Status: Active Military use: Yes Intended use: military, law_enforcement, tactical, home_defense, Military, Law Enforcement, Home Defense