Hodgdon Powder RETUMBO Magnum Rifle Powder is a very slow-burning rifle powder for reloaders preparing compatible large-capacity magnum cartridges, including the 7mm Remington Ultra Magnum and .300 Remington Ultra Magnum. It's designed to support high-velocity performance for big-game hunting across varied conditions. Its temperature-stable formulation helps maintain performance as conditions change. Follow published load data for your cartridge and components.