.375 Remington Ultra Magnum

The .375 Remington Ultra Magnum, also known as the .375 RUM is a .375 rifle cartridge introduced by Remington Arms in 2002. It is a beltless, rebated rim cartridge created by necking up the .300 Remington Ultra Magnum case to .375 caliber with no other changes. The .375 Remington Ultra Magnum is second only to the .378 Weatherby Magnum in cartridge-case capacity. Factory loadings are strong, but relatively sedate when one considers the true potential of the cartridge. Remington factory loads push a 300 grain (19 g) bullet at 2760 ft/s (840 m/s), producing 5070 ft·lbf (6.88 kJ) of energy. A handloader can increase the muzzle velocity of this bullet to a maximum of 2950 ft/s (900 m/s,) developing 5800 ft·lbf (7.9 kJ).

General information
The primary use of this cartridge should be hunting large, thick-skinned game. It is powerful enough to kill any land animal and, with its high velocity, can do so at fairly long ranges. One should note that such performance comes at the price of a heavy recoil: in a sporting-weight rifle of ~8 lb (3.6 kg), this cartridge can produce a fierce 80 ft·lbf (108 J) of recoil (approximately 3.5 times that of a .30-06.)  This is well beyond the limits of most shooters.

There is a good selection of .375 in (9.53 mm) bullets available that are suited to the high velocities of the .375 RUM, and boat tail bullets help to further extend the useful range.

Currently, only Remington makes production rifles in this chambering (Savage previously did so.) Remington and Nosler are the only source of factory ammunition. Loading dies and reloading data are readily available to the handloader.