Pump-action shotguns manufactured by Mossberg are consistently high-quality, well-designed, and reasonably priced. The Mossberg 500 line of firearms is their most well-known product. The Mossberg 590 line of tactical shotguns is without a question the most well-known subgroup of the 500. In the 590 line, Mossberg modified their 500 design to meet military specifications. This pump-action, tube-fed shotgun is available in 12-gauge, 20-gauge, and.410 calibers. The first Mossberg 590 made for the military had a 20-inch barrel, a parkerized finish, a metal safety and trigger system, and a six-round magazine tube. The civilian 590s have polymer triggers and trigger guards. The "clean-out cap" is present on every 590. With the 590, the magazine cap simply threads off, making it simple to clear the magazine tube inside. Standard model 590s come with the clean-out cap, polymer safety and trigger units, and bead sights. The barrels vary from 14 to 20 inches, and magazine capacities are six to eight rounds. The 590A1 is made according to MIL-SPEC. It has an eight-round capacity, a 20-inch heavy-walled barrel, and either ghost ring or bead sights, as well as a bayonet lug. The 590M series are standard 18.5- or 20-inch 590s that have been modified to accept magazine feeds. It uses 5 to 20-round cartridges. The SPX variant has a combination of ghost ring sights. The 590 Shockwave line has 14-inch barrels, and only pistol grip stocks.