Introduced by Westley Richards in 1909 as a proprietary cartridge for their bolt action rifles, this round has a rebated rim of lesser diameter than the case body in order that it would fit a standard diameter Mauser bolt face. This is another very popular round for use against big game. 

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