While still unreleased to the public, the cartridge went on to set world records for accuracy including the first ten 10X in 1,000 yards (910 m) benchrest shooting.

[4] The cartridge was created by necking down the .378 Weatherby Magnum to accept a .308 in (7.8 mm) diameter bullet.

The United States Army’s Redstone Arsenal requested a rifle cartridge that could develop 6,000 ft/s (1,800 m/s) for the effects of light bullets against armor.

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).

However, when launching 30 gr (1.9 g) bullets which are extremely light for caliber as the Redstone Arsenal contract specified, required the use of relatively faster propellants.

However, the hunting public and target shooters used 150 gr and heavier bullets, which require slower burning powders due to the extreme overbore nature of the cartridge.

Since this is a small bore caliber, hunting with the .30-378 Weatherby Magnum may commonly be limited to game less than 2,000 lb (910 kg).

[3][5] The Thompson Long Range shooting school uses the .30-378 Weatherby due to its high accuracy and reliable performance.