The cartridge is essentially a .416 Rigby necked up to accept a .458 in (11.6 mm) bullet, although with a higher operating pressure and much of the original taper removed.

In 1993, Paul Roberts (at that time proprietor of John Rigby & Company) embarked on an elephant hunt in the Zambezi Valley.

Paul Roberts felt that a cartridge with a greater bullet-weight and a larger caliber would have been more effective in the scenario.

Once he returned to the United Kingdom, he necked-up the .416 Rigby case to .458 caliber, resulting in a cartridge remarkably similar dimensionally to the older .460 Weatherby Magnum.

Unlike the .458 Winchester Magnum and .458 Lott, a 500-grain (32 g) bullet can be loaded to 2,500 ft/s (760 m/s) in the .450 Rigby without exceeding acceptable pressures.

[4][5] Such loads generate formidable recoil from standard weight rifles when unequipped with effective muzzle brakes, however.

[6] Among commercial sporting cartridges, only the .460 Weatherby Magnum offers a performance advantage over the .450 Rigby, at least in the .458-inch diameter.

The .450 Rigby was designed primarily to harvest heavy, thick-skinned dangerous game animals in Africa.

The .450 Rigby is capable of exceeding the range of velocities within which many .458 caliber (11.6 mm) bullets are designed to function.