This is Roy Weatherby's idea of the ultimate elephant cartridge. The .378 Weatherby Magnum was introduced in 1953 as a replacement for the previous .375 Wby. Mag. The .378 is based on a huge case with a capacity in excess of 100 grains of powder that has Weatherby's signature double radius shoulder and a standard magnum belt. Despite its unusual nomenclature, the .378 uses standard .375" bullets.

The factory ballistics for the .378 Weatherby are impressive, to say the least. Weatherby claims a muzzle velocity (MV) of 3150 fps with a 270 grain Barnes X-Bullet and 2925 fps with a 300 grain FMJ bullet in a 26" test barrel. The muzzle energy (ME) is 5948 ft. lbs. for the 270 grain bullet and 5966 ft. lbs. for the 300 grain bullet.

According to the A-Square Handloading Manual Any Shot You Want their Monolithic Solid bullet can be driven to a MV of 2752 fps by 106.0 grains of RL22 powder, and a MV of 2911 fps by 110.0 grains of RL22. The latter load had an average pressure of 61,000 psi. These loads used A-Square cases and CCI primers, and were tested in a 26" barrel.

Note: A complete article about the .378 Weatherby Magnum can be found on the Rifle Cartridge Page.