6.5-300 Weatherby Magnum

The 6.5-300 Weatherby Magnum is a modern magnum cartridge with roots in Weatherby’s continuing pursuit of velocity. Officially introduced in 2016, the 6.5-300 Weatherby Magnum was derived by necking down the powerful .300 Weatherby Magnum case to accept a 6.5mm (.264 caliber) bullet. This innovation resulted in one of the fastest commercial 6.5mm cartridges ever produced. The development was directly influenced by a growing demand for high-velocity, flat-shooting cartridges that could excel in both long-range target shooting and hunting. Weatherby’s legacy of high-performance belted magnums, which began in the mid-20th century, is reflected in the 6.5-300’s case design and pressure tolerances. By combining the voluminous .300 Weatherby case with the inherently accurate 6.5mm bullet, Weatherby created a cartridge that pushed the boundaries of ballistic performance in its class.

For reloaders, the 6.5-300 Weatherby Magnum offers unique opportunities and challenges. Its primary applications are in long-range hunting and precision shooting, where a flat trajectory and immense downrange energy are essential. The cartridge is especially prized by hunters targeting medium-sized and large game at extended distances, owing to its ability to retain velocity and deliver substantial terminal performance far beyond the capabilities of many other 6.5mm cartridges. Competitors in extreme long-range shooting disciplines have also adopted the 6.5-300 Weatherby Magnum for its impressive combination of speed and ballistic coefficient, making it a favorite for pushing the envelope at 1,000 yards and beyond. For reloaders, this cartridge rewards careful attention to detail with handloading, especially when fine-tuning loads for accuracy and managing pressures in Weatherby’s proprietary rifles.

Target species for the 6.5-300 Weatherby Magnum typically include North American game such as mule deer, pronghorn, elk, and even moose, as well as African plains game like kudu or springbok. The cartridge’s high velocity and energy transfer make it well-suited for ethically taking these animals at ranges where other cartridges might struggle. While suitable for most big game, some reloaders may find it to be more powerful than necessary for smaller deer or varmint hunting, though it remains highly capable for those uses with appropriate bullet selection. Its long-range prowess is also valued by hunters tackling western terrains or wide-open spaces, where shots beyond 300 yards are routine and performance at distance equates to cleaner, more humane harvests.

When it comes to reloading the 6.5-300 Weatherby Magnum, bullet weights typically range from 127 grains up to 140 grains, with most factory offerings centered around the 130–140 grain mark. Heavier projectiles maximize ballistic coefficient and energy retention, making them ideal for longer shots and larger game. The cartridge’s magnum case design provides ample powder capacity but also results in significant throat erosion over time, a factor reloaders should be mindful of when working up loads, especially for high-volume target shooting. Typical muzzle velocities with 140-grain bullets can exceed 3,300 feet per second, delivering unmatched flatness and minimal drop at extended ranges. Handloaders benefit from selecting high-quality, temperature-stable powders and match-grade primers to optimize consistency and accuracy. Careful attention to brass preparation and COAL (cartridge overall length) is also crucial due to the high pressures involved in this magnum round, ensuring both safety and long barrel life.