Originally designed as a black powder cartridge, the .303 British was the first loaded with a smokeless propellant called Cordite around 1892. The .303 served as a British military cartridge until the 1950's and at one time was an extremely popular big game cartridge. In the hands of farmers and natives, this cartridge with its long .311" bullet has probably killed more African game than any other. Even today the .303 British continues to be quite popular there as well as in Canada. Not much is said or written about the .303 British these days, mainly because those who still use it are hunters and not writers. But it continues to get the job done just like a number of other mild mannered cartridges that have become classics in their time. Sierra,Speer, and Hornadyoffer the .311" bullets of various weights. Some rifles with a bore and groove diameters on the minimum side will also handle .308" bullets about as well. When loaded with a 150 grain spitzer at 2700 fps, the .303 British will kill deer just as dead, just as quick, as the .308 Winchester. Heavier bullets are best for bigger game. Regardless of what bullet is loaded in the .303, H335is an excellent powder. 

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