.375 Rem. Ultra Mag. Load Data & Reloading Guide

The .375 Remington Ultra Magnum, often referred to as the .375 RUM, was introduced in the early 2000s by Remington as part of their Ultra Magnum series. This caliber was developed to provide a powerful magnum cartridge suitable for large game hunting. It shares the lineage with the .404 Jeffery, providing a modernized case for heightened ballistic capabilities.

The .375 RUM features a rebated rim and a beltless design, optimizing case capacity for substantial powder loads. It typically accommodates bullets with a diameter of .375 inches, with common bullet weights ranging from 270 to 350 grains. The case length of 2.850 inches, coupled with a maximum overall length of 3.600 inches, ensures compatibility with standard magnum action rifles. This results in impressive velocities and energy levels, notably increasing effectiveness at extended ranges.

Ballistically, the .375 RUM is known for its flat trajectory and high energy retention, making it ideal for large and dangerous game. It is capable of achieving muzzle velocities exceeding 2900 feet per second with 270-grain bullets, generating energy levels sufficient for the largest North American game and African big game such as buffalo and elephant. The cartridge's ability to maintain performance over long distances makes it a favored choice for hunters engaging in challenging environments.

For reloaders, the .375 RUM offers considerable advantages due to its large case capacity, which enables experimentation with various powder types and loading techniques to optimize performance for specific applications. The absence of a belt simplifies resizing processes, contributing to longer case life and ease of management. Reloaders can tailor their ammunition to achieve specific performance characteristics, whether optimizing for speed, energy, or improved downrange accuracy.