.375 Rem. Ultra Mag. Load Data

Caliber Overview

Introduced by Remington Arms in 1999, the .375 Remington Ultra Magnum (RUM) was designed to deliver magnum-class performance worthy of North America's largest game and Africa's dangerous species. Built on the lengthy .404 Jeffery case—stretched out and necked down to accept .375-inch bullets—the .375 RUM stands among the most powerful .375 cartridges available to civilian hunters. Remington sought to compete with established heavy-hitters like the .375 H&H Magnum and .375 Weatherby Magnum, offering a rimless, beltless design to feed smoothly in bolt-action rifles. This lineage gave the .375 RUM outstanding case capacity and velocity, alongside improved feeding reliability and case life, all thoughtfully designed for reloaders who demand both strength and modern efficiency.

In the field, the .375 Rem. Ultra Mag serves adeptly for hunting some of the planet's toughest and largest animals. Its immense energy and flat trajectory make it a serious contender for African dangerous game such as cape buffalo, lion, and elephant, as well as North American species like Alaskan brown bear and moose. Its power also makes it well-suited for thick-skinned game at extended ranges, where deep penetration and strong bullet construction are mandatory. Given its magnum-level recoil and significant muzzle blast, the .375 RUM is most often chosen by experienced shooters whether for dangerous game safaris or remote wilderness hunts where stopping power can be crucial. Reloaders appreciate the cartridge for its high velocity potential and broad bullet compatibility, which translate into flexible hunting applications.

Target species for the .375 RUM include virtually all dangerous game, as well as large plains game and heavy-bodied animals in any continent. While its size and recoil may be excessive for deer or antelope, the cartridge truly shines on elk, moose, bison, grizzly bear, and African species where quick, ethical kills and deep penetration through thick skin, bone, and muscle are paramount. Though many American hunters might find the .375 RUM too potent for routine whitetail use, seasoned reloaders targeting multi-species adventures or once-in-a-lifetime expeditions often select this cartridge for its well-rounded effectiveness against the world’s most challenging quarry.

Bullet weights in the .375 RUM commonly range from 235 to 350 grains, with the 250-, 270-, and 300-grain options being the most popular among reloaders. These allow careful tailoring to the intended game and shooting distance: lighter bullets offer flatter trajectories for long-range shots, while heavier projectiles maximize energy transfer and penetration for dangerous game. Premium bonded and monolithic bullets are widely recommended for this cartridge, given its velocity potential and the size of animals typically hunted. The .375 RUM’s case length of 2.850 inches and large powder capacity provide ample space for slow-burning magnum powders, and its beltless design contributes to smooth feeding, reliable headspacing, and longer case life—qualities highly valued by dedicated handloaders tackling the largest game.