The .300 Weatherby Magnum is a .30 caliber rifle cartridge created by Roy Weatherby in 1944 and produced by Weatherby. It has become the most popular of all the Weatherby cartridges.
Roy Weatherby already had experience with other custom cartridges such as his own .270 Weatherby Magnum when he created the .300 Weatherby. Like most of his other magnum cartridges, this is based on a blown-out .300 H&H Magnum case, using the signature Weatherby double-radius shoulder. The Weatherby was first introduced in 1944, and the .300 Winchester Magnum was introduced in 1963.
In recent years, Remington, Winchester and Ruger have produced rifles in this caliber, and most major ammunition manufacturers now supply factory loads.

