The .30-378 Weatherby Magnum is a .30 caliber, belted, bottle-necked rifle cartridge. The cartridge was developed in response to a US Army military contract in 1959. While still unreleased to the public, the cartridge went on to set world records for accuracy including the first ten 10X in benchrest shooting. It is currently the highest velocity .30 caliber factory ammunition available. Cartridge origin The .30-378 was originally designed by Roy Weatherby as an anti-personnel/anti-materiel military cartridge for a government contract. The cartridge was created by necking down the .378 Weatherby Magnum to accept a diameter bullet. The United States Army’s Redstone Arsenal requested a rifle cartridge that could develop for the effects of light bullets against armor. The .30-378 Weatherby Magnum was able to attain over . Using a slower burning and denser propellant, the .30-378 Weatherby Magnum surpassed the US Army’s requirement of . However, the shooting public had to wait until 1996 for Weatherby to release the cartridge. In the meantime, the .30-378 Weatherby Magnum had gone on to set world records in benchrest competitions. Earl Chronister, shooting a .30-378 Weatherby Magnum shot the first ever ten shot 10X with the first nine shot to 3.125 inches and the tenth flyer for an overall group of 4.375 inches. This record stood for over 30 years. Several variations of the .30-378 Weatherby Magnum were created by custom ammunition manufacturers, known as wildcatters. Hammond rifles and H-S Precision were among the several custom gun manufacturers who chambered and built rifles long before Weatherby got around to releasing the rifle to the public. In 1991 Shooting Times editor Layne Simpson met with Ed Weatherby, the son of Weatherby Inc. founder Roy Weatherby, and urged him to release the .30-378 Weatherby to the public as a standard chambering in the Mark V action. In 1995 Layne Simpson built a rifle chambered for the .30-378 Weatherby and developed loading data and passed the data on to Norma Precision to provide a basis for their factory loaded ammunition. Design and specification The .30-378 Weatherby Magnum utilizes the .378 Weatherby Magnum as a parent cartridge. The .378 Weatherby case was necked down to accept a .30 caliber (7.62 mm) bullet while preserving the double radii shoulder of the parent case. The resulting case held a greater volume than any previous commercial cartridge. When the cartridge was created by Roy Weatherby in 1959 there were no