Introduced in 1961, all model 500s are based on the same basic design. Originally using a single action bar this was changed to dual action bars in 1970, which are (at least in theory) less likely to bind than a single action bar design. A single large locking lug is used 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 5-shot tube will not fit a gun with a 7-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.