A self defense rifle has to perform the first time, every time. The ultra-reliable A.R.G.O. system incorporated into the new Benelli MR1 does it for the U.S. military, and makes the MR1 the best home defense rifle available. MR1 self defense guns are chambered in 5.56 mm NATO (.223 Remington) and use the battle-proven Auto Regulating Gas Operated (A.R.G.O.) system—the same system developed by Benelli for the M1014 (M4) and used for over a decade in multiple conflicts by the United States Marine Corps.Built to the same tough military specifications and embodying the solid reliability that the U.S. Marines rely upon, the MR1 has no equal among home defense weapons. It features a stainless steel, self-cleaning piston that operates directly against the proven rotating bolt, thereby eliminating the need for complex linkages found on other, inferior gas systems. This piston-driven system, perfected by Benelli, incorporates a gas port located just forward of the chamber, where the gases are hotter and cleaner, resulting in less fouling and more reliable cycling. The result—a Benelli carbine with features rivaling all other home defense rifles, including Marine-tough reliability and the ability to function in the harshest environmental conditions.