Remington Ultra Magnum, or RUM, refers to a "family" of cartridges developed in 1999 and the early 2000s by Remington Arms. All of the RUM cartridges are based on the .404 Jeffery non-belted magnum cartridge. There is a long-case line, as well as a shortened version designed to fit a short rifle action (such as a .308 Winchester). The long case is very large and provides performance that exceeds existing commercial magnums, such as the .300 Winchester Magnum and .300 Weatherby Magnum.