The magazine tube is located below the barrel, and is screwed into the receiver. A single large locking lug is used to secure the breech. Originally using a single action bar that was known to bind and even break, this was changed to dual action bars in 1970, following the expiration of Remington's patent on the double action bar design. Introduced in 1960, all model 500s are based on the same basic concept designed by Carl Benson. Marines assigned to the Commander of the Seventh Fleet's Fleet Anti-terrorism Security Team (FAST)'s Third Platoon, practice using the M590 shotgun The Revelation 310 and the New Haven 600 were also variations of the 500 series produced by Mossberg under different names.
Model numbers included in the 500 series are the 500, 505, 510, 535, and 590. 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.
Mossberg 500 is a series of pump action shotguns manufactured by O.F. Varies, 2+1 to 8+1 rounds internal tube magazine
