Compared to the massive, belted .30-378 Weatherby (right), the non-belted .300 RUM case is smaller, yet it provides more velocity than many other .300-caliber Magnums.
The decade that bridged the change of centuries in 2000 was a fertile time for new rifle cartridges. Between 1999 and 2001, Remington introduced four Magnum cartridges that covered almost everything from deer to dangerous game.
Remington picked the most popular starting point—.30 caliber—and developed a new, large-capacity case about 2.8 inches long to create the .300 Remington Ultra Mag. Remington had finally answered Winchester’s 1963 debut of the still-popular .300 Winchester Magnum. Better late than...