Here is an awesome reference to the 303 Savage:

http://www.chuckhawks.com/303_savage.htm

but in a nutshell

Despite its " .303" nomenclature, the .303 Savage is usually reloaded with standard .308" (.30 caliber) bullets. The .303 Savage case is a rimmed, bottleneck type with a rim diameter of .505" , a base diameter of .442" , a shoulder angle of 16 degrees, and a length of 2.015" . In a practical sense, it has about 1-2 grains greater useful capacity with common powders than the .30-30 case. Like the .30-30, the .303 has always been loaded with flat point or round nose bullets, even though the Savage Model 99 rifle used a rotary magazine which could (and did in other calibers) accommodate spitzer bullets