[1] The 500 series comprises widely varying models of hammerless repeaters, all of which share the same basic receiver and action, but differ in bore size, barrel length, choke options, magazine capacity, stock and forearm materials.

[2] Designed in 1961 by Carl Benson, the Mossberg 500 was created mainly for use by hunters, but quickly found itself in use by law enforcement because of its reliability and low cost.

[2] In the 1970s, the M500 was submitted for military use, but failed to meet the MIL-SPEC 3443E protocol,[2] which involves firing 3,000 rounds of shells with no more than two malfunctions.

[2] M500s began to be purchased by the US military in limited numbers, with the first order consisting of approximately 5,900 shotguns for the Navy and Coast Guard.

[4] To maintain its low cost, Mossberg continued to produce the M500 for civilian and police markets, and in 1987, designed the M590 specifically for military use.

[2] Replacement for the M500 came as early as 1999,[5] when the Marine Corps adopted the semi-automatic M1014 Combat Shotgun, which became standard issue by 2001.

[10] In the wars in Iraq and Afghanistan, M500 shotguns were primarily used for breaking locks and hinges during door breaches.

[11] In 2009, U.S. Army Special Forces Groups procured Military Enhancement Kits to provide a standardized shotgun configuration based on the Mossberg 500.

The majority of the kits convert the standard issue shotgun to a 14" compact model with a 16" accessory breaching barrel, H92239-09-P-0113.

[14] The name "Model 500" covers an entire family of pump shotguns designed to chamber 3-inch (76 mm) "magnum" shells.

[15][16][17] The standard finish for the Model 500 is an anodized aluminum alloy receiver and a polished and blued barrel.

The Model 590A1 has an aluminum trigger guard and safety, a heavier barrel, and a bayonet lug (although some versions of the 590 also have bayonet lugs), intended for military use under extreme conditions and rough handling; the metal trigger guard was added in response to the 3443G materials requirements, and the heavy barrel was added at the request of the Navy to prevent barrel deformation if the shotgun caught in the closing of heavy steel ship doors.

590A1s with 14" barrels are Title II firearms, and may be purchased only by non-prohibited persons in NFA-legal states, after completing BATF transfer forms.

A heat shield and bayonet lug are required for military 3443G Type I riot shotguns,[18] and some 590A1s are so equipped.

The standard Model 500 uses a 14-inch (36 cm) length of pull (LOP) for the stock, which is suitable for adult shooters of average or greater size.

The shortest barrel length available for the eight- and nine-shot models is 20 inches (51 cm), which fits flush with the long magazine tube.

Special purpose models may be equipped with a variety of specialty parts which may include adjustable stock, "Speedfeed" stock that holds four additional rounds of ammunition, pistol grip, ghost ring and fiber optic sights, Picatinny rail, forearm band, heatshield, ported barrel, muzzle brake, and even a bayonet lug.

All special purpose models come only in black trim with either blued, non-glare matte blue, or parkerized finishes and now come with drilled and tapped receivers for scope and optics mounting.

It is available in three models; one is a derivative of the Shockwave, the other two are variants of the base 590, one having ghost ring sights and a heat shield, the other without.

It comes with a youth-sized stock, a vertical foregrip, and a special muzzle brake and spreader choke (to help produce wider patterns when using buckshot) on an 18.5-inch (47 cm) bead sight barrel.

A 90-grain slug generates energy close to (and in some manufacturer claims, exceeding) a .357 Magnum when fired from a full length barrel.

It is packaged with an introductory video covering use and safety, and some versions have a laser sight mounted in the foregrip.

It features the same sliding tang safety on the top rear of the receiver, twin action bars, and dual extractors seen on other models.

It avoids restriction as a short barrel shotgun under Title II of federal firearm laws by remaining over 26 inches (66 cm) in length and not being made to have a shoulder stock.

The bird's head grip meant the Shockwave is deemed as a regular long gun similar to a Mare's Leg, and not a "handgun".

The model 590DA offers a longer, heavier trigger pull, to reduce the chance of an accidental discharge by the operator, and was targeted at the police market.

It uses special blank cartridge to propel a shaft with an optional floating head and a light rope attached to it; a canister hung below the barrel to hold the line spool.

A test of the Mossberg 500 with line launcher by the BoatUS Foundation showed an average range of over 330 feet (100 m) with the floating head.

This can be removed by taking off the barrel, pointing the shotgun downward, and shaking it back and forth lightly until the dowel shows out of the end of the magazine tube.

Except for the Maverick 88, all current production Mossberg models have a pre-drilled receiver for installation of an upper Picatinny rail for mounting various optics such as red dot sights.