This consideration prompted the Federal Cartridge Company to introduce the 215 Magnum primer specifically for this round.

The impetus for the development of the .378 arose from Roy Weatherby’s extensive field testing conducted in African hunting grounds.

In order to gain access to markets across the African continent by accommodating the 10.16 mm (.40 caliber) minimum bullet size required for use on dangerous game in some countries,[5] Weatherby soon necked the .378 to 11.63 mm (.458 caliber) and introduced the resultant cartridge as the .460 Weatherby Magnum in 1957.

The .378 Weatherby generates considerable free recoil with full-power loads, for an average of 72 ft·lbf from a 9 lb rifle.

[9] It should also be noted that Weatherby Mark V rifles chambered in this cartridge are equipped from the factory with removable muzzle brakes that greatly reduce felt recoil.