The .300 Remington Ultra Magnum (RUM) is a centerfire rifle cartridge introduced by Remington in 1999. It is based on the .404 Jeffery case, necked down to .30 caliber. The .300 RUM is known for its high velocity and significant energy output, making it suitable for long-range shooting and big game hunting, including elk, moose, and large African game. It delivers flat trajectories and high terminal ballistics, which appeals to hunters needing to make precise shots over long distances. The cartridge is compatible with standard long-action rifles and provides performance comparable to other large .30 caliber magnums, such as the .300 Winchester Magnum and the .300 Weatherby Magnum.