The Mossberg 500 is a shotgun manufactured by O.F. Mossberg & Sons. Rather than a single model, the 500 is really a series of widely varying hammerless, pump action repeaters, all of which share the same basic receiver and action, but differ in bore size, barrel length, choke options, magazine capacity, and "furniture" (stock and forearm) materials.
All modern 500s are based on the same basic design, using dual action bars, which are (at least in theory) less likely to bind than a single action bar design, and a single large locking lug to secure the breech. The magazine tube is located below the barrel, and is screwed into the receiver. The slide release is located to the left rear of the trigger guard, and the safety is located on the upper rear of the receiver (often called a "tang safety"). Sights vary from model to model, from simple bead sight to a receiver mounted ghost ring or an integrated base for a telescopic sight. Most models come with the receiver drilled and tapped for the installation of a rear sight or a scope base. The factory scope base is attached to the barrel via a cantilever-type mount, which places the scope over the receiver but keeps it with the barrel if the barrel is removed.
Intended for use in harsh and dirty conditions, such as waterfowl hunting or combat, the Model 500 series is designed to be easy to clean and maintain. All Model 500s feature interchangeable barrels (given a particular gun's mag capacity; a barrel designed for a 4-shot tube will not fit a gun with a 6-shot tube) which may be removed without the use of tools, by loosening a screw on the end of the magazine tube, which allows the barrel to be removed. The bolt locks into a locking lug located on the top of the barrel, ensuring a solid bolt-to-barrel connection and not relying on the receiver for any locking strength. The trigger assembly, which includes the trigger, hammer, sear, and trigger body with guard, can be removed by pushing out one retaining pin and pulling downwards on the guard (if a pistol grip is installed, it usually must be removed first as virtually all such grips obstruct the removal of the trigger body). The elevator can be removed by squeezing the sides together, freeing the pivot pins from the receiver. The forend can then be moved to the rear, allowing the bolt and bolt carrier to drop out, and then the forend can be removed by moving it forward. The cartridge stop and interrupter will then fall free, leaving just the ejector and the safety in the receiver, held in by screws. The magazine spring and follower may be removed by unscrewing the tube from the receiver (this may be difficult on some new 500s). This level of field stripping is sufficient to allow all components to be cleaned.
Model 500 options
The name "Model 500" covers an entire family of pump shotguns designed to chamber 3" (76.2mm), "magnum," shells. The standard model holds five 2 3/4" (70mm) or four 3" shells in the magazine and one in the chamber. The Model 500 is available in 12 gauge, 20 gauge, and .410 bore, with the 12 gauge being the most popular and having the most optional features available.
The standard finish for the Model 500 is an anodized aluminum alloy receiver and a polished and blued barrel. Some models come with a matte black painted receiver, and a matte blued barrel. Steel receiver models are parkerized, with parkerized barrels. Mossberg also offers camouflage painted models, in a number of different patterns. Stocks are either wood or composite, with the composite stocks being matte black or camouflage to match the rest of the gun. A special model called the Mariner is available with the Marinecote finish, a silver finish that is highly corrosion resistant. Mariner models use the black composite stocks.
Model 500 vs. Model 590 vs. Model 590A1
The primary difference between the Model 500 and Model 590 is in magazine tube design. The Model 500 magazines are closed at the muzzle end, and the barrel is held in place by bolting into a threaded hole at the end of the magazine tube. Model 590 magazines are open at the end, and the barrels fit around the magazine tube and are held on by a nut at the end. The Model 500 magazine facilitates easy barrel changes, as the barrel bolt serves no function other than holding the barrel in place. The Model 590 magazine facilitates easy cleaning and parts replacement, as removing the nut allows removal of the magazine spring and follower.
Parkerized Mossberg 590A1 with M7 Bayonet, upper picatinny rail, and modified standard 590 Heat shield
The Model 590A1 is a Model 590 with an aluminum trigger guard and safety, and a heavier barrel, 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. The 590A1 is generally sold through military and law enforcement channels, though in most jurisdictions the 18.5" and 20" models may be legally purchased by private persons. 590A1s with 14" barrels are Title II firearms, and may be purchased by private persons in NFA-legal states.
The riot gun versions of the Model 500 (Persuader and Mariner) are available with an 18.5" or 20" (47cm or 51cm) barrel depending on magazine capacity. The 590 is only available with a 20" barrel and flush-fit magazine tube. The 590A1 is available with a 14" (35.5cm), 18.5", or 20" barrel. One model sold as Model 590 (catalog item 51663) is technically a 590A1, as it uses the heavy barrel and military trigger group, but unlike models designated 590A1 it is sold on the civilian market.
Unlike Model 500 and 590 shotguns (with the exception of ghost-ring sight 590 models), Model 590A1 shotguns cannot be easily fitted with the factory heat shield, due to the heavy barrel. A heat shield and bayonet lug are required for military 3443G Type I riot shotguns, and some 590A1s are so equipped, but it is not clear if the 590A1 heat shields have ever been offered for sale outside of the military market.
Bantam and Super Bantam models
The standard Model 500 uses a 14" (35.5cm) length of pull (LOP) for the stock, which is suitable for adult shooters of average or greater size. The Bantam models use a 13" (33cm) LOP stock and a forend that sits further back than the standard model. The Super Bantam stock includes two recoil pads and a stock spacer. By using the short pad, the LOP can be reduced to 12" (30cm); with the spacer and longer pad, the LOP is 13". A number of different models are offered with Bantam and Super Bantam stocks, or they can be ordered as accessories and fitted to any Model 500.
The new model 505 Youth shotgun, introduced in 2005, is similar to the Bantam but scaled down further. The 505 has a 12 inch pull buttstock (compared to a standard model's 14 inches, or a Bantam's 13 inches), a 20 inch barrel, and a four shot magazine tube. The 505 is available in 20 gauge and .410 bore. Parts are not interchangeable with other model 500 variants.
The Model 535, new for 2005, is similar to the Model 500, but with a lengthened receiver that can fire 3-1/2" (89mm)shells, in addition to 2-3/4" and 3" shells. The 535 is a less expensive alternative to the Mossberg 835 Ulti-Mag, but the 535 lacks the 835's overbored barrel. The non-overbored barrel of the 535 does, however, allow the use of slugs, which cannot be used in the overbored barrel of the 835. Model 535 barrels are not interchangeable with model 500 or model 835 barrels, but 535 barrels are available in smoothbore and rifled in a variety of vent ribbed, barrel lengths and different sights. The 535 is, at present, offered only in sporting models, no riot or combat models are available.
The Model 500 comes in a variety of different receiver configurations, whose main difference is the magazine configuration. The basic Model 500 comes with a magazine tube capable of holding five 2 3/4" shells, which is called a six shot model (a full magazine plus a round in the chamber). The 500 is also available with an extended magazine tube that holds seven rounds, making an eight shot model. The 590A1 is available with five and eight shot magazines, sold as six and nine shot models respectively.
The variants with the extended magazine tubes use different barrels, as the barrel is held in place by attaching at the end of the magazine tube. The shortest barrel length available for the eight and nine shot models is 20 inches (51cm), which fits flush with the long magazine tube. A ribbed 28 inch (71cm) modified choke field barrel was also manufactured for the 8 shot model 500. The shortest barrel for Title I six-shot models is 18.5 inches, while military and law enforcement personnel (as well private persons in NFA states) can also get a 14 inch barrel (the 590 Compact), which is flush with the six shot model's magazine.
Model 500 variants
The Model 500 is available in many variants, for a wide variety of applications. The ease of changing barrels on the Model 500 means that a single shotgun may be equipped by the owner with a number of different barrels, each for a different purpose. As sold, the Model 500 is generally classed into two broad categories: field models and special purpose models.
Field models are the basic sporting models. They are available with a variety of barrel lengths and finishes, and may be set up for waterfowl hunting, upland game hunting, turkey hunting, or shooting slugs. Most smoothbore models come with interchangeable choke tubes and vent rib barrels, while the slug models come with rifle sights or scope bases, and may have smooth cylinder bore or rifled barrels.
Special purpose models
Special purpose models are intended for use for self defense, police, or military use. The Model 590 and the eight shot Model 500s are only sold as special purpose models. Special purpose models have short barrels, either 18.5 inches for the six shot models, or 20 inches for the eight and nine shot models.
Special purpose models may be equipped with a standard shoulder stock, a "Speedfeed" stock that holds 4 additional rounds of ammunition, or a pistol grip stock. Special purpose models come with plain barrels (no vent rib) with bead sights or ghost ring sights. Some bead sighted models may include heat shields.
It should be noted that "Special Purpose" models are not the same as "Law Enforcement" models; the latter have heavier duty barrels, safeties, and trigger guards, and will stand up to harder use.
Law Enforcement Models
Mossberg shotguns designated "law enforcement models" are 590A1s. 590A1s differ from other 500/590 shotguns, in that they have heavy barrels, metal trigger guards, and metal safeties. 590A1s are available in 14", 18.5", and 20" barrels. The 590A1 is also used by the U.S. and allied armed forces, having been designed to meet the stricter standards outlined by the U.S. Army.
Home Security model
The model 500 HS410, or "Home Security" model, is only available in .410, and is specifically designed for defensive use. It comes with a youth sized stock, a vertical foregrip with, in some versions, a built in laser sight, and a special muzzle brake and spreader choke on an 18.5 inch (47 cm) bead sight barrel. The .410, while by far the least powerful common shotgun chambering, still generates energy in excess of a .357 Magnum, and the spreader choke produces wider patterns, as well as less chance of wall penetration, in the short ranges to be expected in a defensive situation. This model is targeted at the novice user, who needs a simple, easy to use yet effective defensive weapon, and is packaged with an introductory video covering use and safety.
Accessories and combinations
The Mossberg 500 has always been marketed as a multi-purpose firearm. Mossberg sells a wide variety of accessory stocks and barrels, allowing many configurations to be made (including, in the past, a bullpup configured model 500). Mossberg is also the first and only company to ever offer a double action-only model. The model 590DA offers a longer, heavier trigger pull to reduce the chance of a accidental discharge by the operator, and was targeted at the police market.
With the appropriate parts, the same Model 500 can be a field gun, a slug gun, defensive weapon for civilian, police, or military use, trap and skeet gun, or .50 caliber (12.7mm) rifled muzzleloader.
Mossberg has also sold "combination" sets, with a single receiver and more than one barrel. Common examples included a 28 inch field barrel packaged with an 18 1/2 inch cylinder bore barrel for defensive use, or a field barrel and a slug barrel, or a slug barrel and a .50 caliber muzzleloading rifle barrel.
A unique item offered by Mossberg for the Model 500 is a line launcher kit. 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 (100m) with the floating head. Distances of 700 feet (213m) are claimed for the non-floating long distance head.
All Mossberg models including the 835, 535, 500, 505 and 590 (except for Special-Purpose and Law Enforcement models) are shipped with a wooden dowel located in the tube magazine. This is to comply with U.S. migratory bird laws. This dowel reduces and regulates the number of shells that can be loaded in the gun. This can be removed by taking off the barrel and pointing the shotgun downward and shaking it back and forth lightly until the dowel falls out.
Maverick Arms subsidiary
Mossberg also markets a less expensive shotgun under the Maverick Arms name: the Maverick 88, in blued finish, with synthetic stocks. Maverick and Mossberg shotguns share some similar parts,  but Maverick shotguns differ in some ways, such as lacking sling swivel studs and having cross-bolt safeties instead of tang safeties. The factory warranty on Maverick shotguns are limited to one year. Maverick Arms models are assembled in Texas, rather than in Mossberg's main facility in Connecticut.