It’s as if Lego made a shotgun. You snap some parts off, put some on, swap barrels, and your duck gun is a deer gun. Or a turkey gun. Or a home-defense gun or a tactical riot gun. You can change the stock, fore-end, and pad of Mossberg’s Model 500 Flex pump action in less than two minutes, without tools. Available in 11 base models, with 16 accessory parts, the Flex represents the ultimate expression of Mossberg’s shooting-system approach.