The Mossberg 590A1 is the military-specification variant of the Mossberg 590, adopted by the US Armed Forces after passing the MIL-SPEC 3443E testing requirements. The 590A1 features a heavy-walled barrel, aluminum trigger guard, and a metal safety button in place of the polymer components found on consumer models. Standard US military service shotgun alongside the M870. Type: Shotgun Action: Pump-Action Caliber: 12 Gauge Capacity: 8 Year introduced: 1987, USA Weight: 7.25 oz Overall length: 41" Status: Active Military use: Yes Intended use: Military, Law Enforcement