Mossberg 500 is a series of shotguns manufactured by O.F. Mossberg & Sons. The 500 series comprises widely varying models of 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. The name "Model 500" covers an entire family of pump shotguns designed to chamber 3-inch (76 mm) "magnum" shells. The standard model holds five 2.75-inch (70 mm) or four 3-inch (76 mm) shells in the magazine and one in the chamber. 

Season 2

Clovis, a tow truck and junkyard owner who is a cousin of an associate of Jesse Pinkman's, uses a shortened Mossberg 500 to threaten an intruder sleeping in his RV, but puts up his gun when the intruder turns out to be Jesse himself ("Down").

Season 3

A Mossberg 500 Mariner is used by Deputy Bobby Kee before he is axed by one of The Cousins ("Sunset").