Until the advent of the .700 Nitro Express in 1988, this was the largest and most powerful of all the English big game cartridges. Its design, by Jeffery in 1903, was based on an earlier blackpowder round and it was used in double rifles. It is today a formidable cartridge for any type of dangerous big game. 

This text is based on information from “Cartridges of the World”, Hodgdon reloading manual, the cartridge designer and/or own resources.