The 30-378 Weatherby Magnum is a.30 caliber, belted, bottle-necked rifle cartridge that was designed in response to a military contract from the United States Army in 1959. Roy Weatherby created it for a government contract as an anti-personnel/anti-material military cartridge. This white-hot cartridge is based on a 378 caliber cartridge that has been necked down to 30 caliber and loaded with powder. It comes factory loaded with bullets weighing between 165 and 200 grains (10.7 g and 13.0 g), producing muzzle speeds of over 3,500 ft/s (1,100 m/s) and muzzle energies of over 4,750 foot-pounds force (6,440 J).
The cartridge went on to achieve world records for accuracy while still undisclosed to the public, including the first ten 10X in 1,000 yards (910 m) bench rest shooting.
For the impact of light bullets on armor, the US Army's Redstone Arsenal required a rifle cartridge that could develop 6,000 ft/s (1,800 m/s). The.30-378 Weatherby Magnum was capable of reaching speeds of almost 5,000 feet per second (1,500 meters per second). The 30-378 Weatherby Magnum was able to attain over 5,000 ft/s (1,500 m/s), however, while using a slower burning and denser propellant, the .30-378 Weatherby Magnum surpassed the US Army’s requirement of 6,000 ft/s (1,800 m/s). Later, the 30-378 Weatherby Magnum was put to the test for long-range hunting and marksmanship competitions of over 1,000 yards (910 m).