.300 Rem. Ultra Mag Load Data

Introduced in 1999 by Remington Arms, the .300 Remington Ultra Magnum (commonly known as .300 RUM) quickly made its mark as one of the most powerful .30 caliber cartridges available to civilian shooters. Built on the massive, beltless Ultra Magnum case derived from redesigned .404 Jeffery brass, the .300 Rem. Ultra Mag was engineered to deliver superior velocity and energy, surpassing other popular magnums like the .300 Winchester Magnum and the .300 Weatherby Magnum. The intention was to provide long-range shooters and hunters with a high-capacity, high-performance round capable of outstanding downrange ballistic efficiency. Its rapid adoption by reloaders and long-range enthusiasts is a testament to Remington’s successful entry into the magnum market.

The .300 Rem. Ultra Mag’s popularity among shooters stems from its impressive versatility and power, making it exceptionally well-suited for a variety of demanding applications. With its flat trajectory and ability to maintain velocity and energy over extended distances, this caliber is highly prized in long-range hunting and shooting competitions. Reloaders appreciate the .300 RUM for the potential to fine-tune loads for specific purposes, such as optimizing for extreme accuracy or maximizing terminal ballistics for big game. The cartridge’s case capacity offers flexibility in handloading, allowing for a broad selection of powders and projectiles, which further extends its practical range and adaptation for different shooting scenarios.

Hunters most often choose the .300 Rem. Ultra Mag for pursuing large and sometimes dangerous game where deep penetration and enormous energy are required. Its tremendous stopping power makes it an excellent option for North American species like elk, moose, and black or even brown bear. The cartridge’s flat trajectory and retained energy at long distances also make it a popular choice for mountain hunts, where shots across canyons or open tundra may be necessary. While it is certainly capable on medium-sized game such as deer, the full power of the .300 RUM is often considered more than is needed for such animals, with many preferring lighter loads or more moderate cartridges for whitetail-sized targets. The .300 RUM’s power and reach truly shine in settings where a confident, ethical shot at extended ranges is paramount.

When it comes to bullet selection, the .300 Rem. Ultra Mag typically performs best with projectiles in the 165 to 220 grain range. Lighter bullets around 165 to 180 grains are often chosen for flatter trajectories and reduced recoil, ideal for hunting deer or targeting smaller game at long distances. Heavy bullets, including those weighing up to 220 grains, are usually preferred for bigger game or when deep penetration is needed. This bullet weight flexibility allows reloaders to adapt their ammunition for a variety of hunting and shooting needs. The .300 RUM’s capacity for high velocities—often pushing 180 grain bullets at speeds over 3200 fps—means that barrel wear can be greater compared to milder .30 caliber options, and careful load development is essential for achieving the ideal balance between accuracy, barrel life, and terminal performance. Despite this, the .300 Rem. Ultra Mag remains a standout choice for reloaders seeking magnum power, adaptability, and long-range capability in a .30 caliber rifle.