The Mossberg 590 is the service version of the 500 pump-action platform, with a magazine tube that unscrews at the muzzle for cleaning and, on the 590A1, a heavier barrel with a metal trigger guard and safety. Barrels are typically 18.5 or 20 inches and capacity runs from 6+1 to 8+1. Listings cover 12 gauge, 20 gauge and .410 bore builds, including Tactical, Cruiser, Persuader and Shockwave variants. They differ mainly in sights, stock type, heat shield and forend, so compare barrel length and capacity before choosing one.