Mossberg 500, Retrograde, Pump Action, 12 Gauge, 3 Chamber, 28 Vent Ribbed Barrel, Matte Blue Finish, Walnut Stock and Forend, Dual Bead Sights, 5 Rounds 50430 This 500 Retrograde model is a timeless combination of Mossberg hunting pump-action features, highlighted with the classic look of walnut furniture. A throwback to the look of early hunting pumps, Retrograde models feature a walnut stock with checkered grip and vented recoil pad, and matching forend.