The .416 Weatherby Magnum is a belted, bottlenecked cartridge designed by Ed Weatherby and launched commercially in 1989. It is a dangerous-game cartridge intended for the hunting of heavy dangerous game such as elephant and African Cape buffalo. It is considered the most powerful commercial .416 cartridge, besting the Remington, Rigby and Ruger .416s by a velocity of 300 ft/s (91 m/s). Unlike earlier Weatherby cartridges which were designed by Roy Weatherby, this cartridge was designed by Ed Weatherby, the son of Roy Weatherby.
Beginning in the 1960s and through the 1970s, safari hunting in Africa was on the decline, and in turn demand for big-bore cartridges waned. Furthermore, the introduction of the .458 Winchester Magnum, which could be chambered in inexpensive rifles, further put a nail in the coffin of other big-bore cartridges such as the .416 Rigby, which required an oversized rifle action. Due to the lack of interest, ammunition manufacturers like Kynoch ceased operations.
However, by the 1980s, a renewed interest in safari hunting created a demand for big-bore dangerous-game cartridges. In 1988 Remington stepped up to the plate with their iteration of the .416 Hoffman, which was given the name .416 Remington Magnum. Unlike the Rigby, the Remington cartridge utilized the .375 H&H Magnum case and therefore, unlike the .416 Rigby, could be chambered in most firearm actions.
Taking advantage of this momentum, Weatherby introduced their own .416 cartridge in 1989; it was based on the .378 Weatherby Magnum cartridge, which was necked up to accept a .416 in (10.6 mm) bullet.