The .375 Remington Ultra Mag

By Chuck Hawks

In 2001 Remington introduced their .375 Ultra Mag, which is apparently intended to compete with the .378 Weatherby Magnum as the most outsized commercial .375 cartridge. It is based on the .300 Ultra Mag case necked up to accept .375" diameter bullets. Like the .300 Ultra Mag, this huge beltless cartridge is loosely based on the British .404 Jeffery Rimless elephant rifle case and uses a rebated rim design to allow it to mate with standard magnum size bolt faces. The .375 is the only Ultra Mag caliber that throws a heavy enough bullet to even begin to justify the powder capacity of its case, and then only for use on the heaviest game. Using 300 grain bullets it should be an excellent elephant cartridge.

Remington factory loads include a 270 grain bullet at a claimed muzzle velocity (MV) of 2,900 fps and 5,041 ft. lbs. of muzzle energy (ME), and a 300 grain bullet at a MV of 2,760 fps and ME of 5073 ft. lbs. At 200 yards the 300 grain bullet is traveling at 2263 fps and retains 3412 ft. lbs. of energy. These figures were developed in a 24" test barrel.

The reloader can approximately equal these velocities, and in addition has 235 and 250 grain bullets with which to work. Hodgdon reloading data shows that the 250 grain Barnes X-Bullet can be driven to 3090 fps with 103.0 frains of H4831 powder. The 300 grain Swift bullet can be driven to a MV of 2719 fps by 97.0 grains of H4831. These Hodgdon loads used Remington cases and primers and were tested in a 24" barrel.

Note: A complete article about the .375 Rem. Ultra Mag can be found on the Rifle Cartridge Page.

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Copyright 2004, 2013 by Chuck Hawks. All rights reserved.