The Benelli M4 uses a dual-piston ARGO gas system developed for the U.S. Marine Corps. 18.5-inch barrel, ghost ring sights, pistol grip stock, and Picatinny rail. In continuous USMC service since 2000 as the M1014. The gold standard for military semi-auto shotguns. Type: Semi-Automatic Shotgun Action: Gas-Operated Caliber: 12 Gauge Capacity: 5 Year introduced: 2000, Italy Weight: 7.8 oz Overall length: 40" Status: Active Military use: Yes Intended use: Military, Tactical, Law Enforcement, Home Defense