Mossberg 590A1

About the Mossberg 590A1

The Mossberg 590A1 is a heavy-duty, military-specification pump-action combat shotgun manufactured by O.F. Mossberg & Sons. Developed as a purpose-built military variant of the Mossberg 590, the 590A1 is the only pump-action shotgun to have passed the United States Army's demanding MIL-SPEC 3443E endurance and environmental testing protocol, which subjects the weapon to over 3,000 rounds of full-power 12-gauge buckshot along with extensive drop, impact, and environmental abuse tests. The 590A1 was created after the U.S. military identified specific deficiencies in the standard Mossberg 500 platform during evaluation in the late 1970s. Key upgrades over the base 590 include a heavy-walled barrel (originally requested by the U.S. Navy so the weapon could withstand being slammed in the steel doors of frigates without barrel deformation), a metal trigger guard and metal safety button replacing the standard polymer components (required to meet MIL-SPEC 3443G material specifications), and a clean-out magazine tube that allows rapid clearing without full disassembly. The 590A1 features the Mossberg family's signature ambidextrous top-mounted tang safety, dual action bars for smooth and reliable cycling, an anti-jam elevator, steel-to-steel lockup, and dual extractors. Available with 14-inch (NFA/Class III), 18.5-inch, and 20-inch heavy-walled barrels in 6+1, 7+1, and 9+1 capacities, the standard military configuration features a 20-inch barrel with 8+1 capacity, bayonet lug, ghost ring sights, Parkerized finish, and synthetic stock. The 590A1 has been in continuous U.S. military service since 1987 and has been adopted by armed forces and law enforcement agencies worldwide, seeing extensive combat use in Iraq, Afghanistan, and numerous other theaters of operation.

The Mossberg 590A1 is the only pump-action shotgun to have passed the U.S. Army's MIL-SPEC 3443E torture test -- a brutal protocol involving 3,000 rounds of full-power buckshot, repeated drops onto concrete, and extreme environmental exposure. The heavy barrel was born from a U.S. Navy requirement: sailors needed a shotgun barrel tough enough to survive being caught in the slamming steel doors of warships without bending.

Mossberg 590A1 specifications

The 590A1 was the U.S. military's primary combat shotgun from 1987 until the semi-automatic Benelli M4 (M1014 JSCS) began supplementing it in the early 2000s. However, the 590A1 remains in active U.S. military service alongside the M1014, with a new $11.6 million U.S. Army contract awarded to Mossberg in 2025 for additional 590A1 units. The updated MIL-SPEC 3443G specification now requires a metal trigger guard, meaning only 590A1 variants (not standard 500 or 590 models) can meet current military requirements. The 590A1 Class III variant with a 14-inch barrel is restricted to military and law enforcement sales as a short-barreled shotgun under U.S. federal law. The SPX variant adds a Picatinny rail, LPA adjustable ghost ring sight, and M-LOK forend. The Retrograde variant features a walnut stock and forend with a heat shield, recalling the aesthetic of classic military combat shotguns. All 590A1 models use Mossberg's cylinder bore choke, optimized for buckshot and slug patterns at combat distances. The heavy-walled barrel, while slightly increasing weight over the standard 590, provides significantly improved durability and heat dissipation during sustained firing.