Test barrel length: 26 in (66 cm) Source(s): Weatherby [1] / Nosler [2]
The .378 Weatherby Magnum was designed by Roy Weatherby in 1953.[3][4] Although inspired by the .416 Rigby, it is an original belted magnum design with no parent case.[5] The cartridge features a high powder capacity relative to its bore size, and can hold upwards of 7.13 g (120 gr) of powder. This consideration prompted the Federal Cartridge Company to introduce the 215 Magnum primer specifically for this round.[5] The .378 shares the double radius shoulder design found on the other Weatherby magnum cartridges.
The impetus for the development of the .378 arose from Roy Weatherby’s extensive field testing conducted in African hunting grounds. Based on his safari experiences, he believed it to be desirable to improve the performance afforded by his preexisting .375 Weatherby Magnum by devising a larger cartridge more in keeping with the design philosophy of his small-bore cartridges, such as his .300 and .257 Magnums.[6][7]
To promote the .378, Roy Weatherby killed an African elephant with one shot at extended range. In order to gain access to hunters across the African continent and accommodate 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.[8]
The .378 Weatherby generates considerable free recoil with full-power loads, for an average of 72 ft·lbf from a 9 lb rifle. This compares to 23 ft·lbf from a rifle chambered for .30-06 Springfield or 44 ft·lbf for the .375 H&H Magnum. However, the .458 Winchester Magnum generates 78 ft·lbf and the .458 Lott produces 86 ft·lbf of free recoil.[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.
^Ackley, P.O. (1927) [1962]. Handbook for Shooters & Reloaders. vol I (12th Printing ed.). Salt Lake City, Utah: Plaza Publishing. p. 442. ISBN978-99929-4-881-1.
^Any Shot You Want, The A-Square Handloading Manual, pg 604
^Ackley, P.O. (1979) [1966]. Handbook for Shooters & Reloaders. vol II (8th Printing ed.). Salt Lake City, Utah: Plaza Publishing. p. 141. ASINB000BGII48.
^Any Shot You Want, The A-Square Handloading Manual, pg 561