From Wikipedia:
".303 British...is a .311 inch calibre rifle and machine gun cartridge first developed in Britain in the 1880s as a blackpowder round, later adapted to use cordite and then smokeless powder propellant. It was the standard British and Commonwealth military cartridge from 1889 until the 1950s ...In 1910, the British took the opportunity to replace their Mark 6 rounds with a more modern design. The Mark 7 (Mark VII) used a 174-grain (11.3 g) pointed bullet with a flat-base...Perhaps the most famous single .303 British round ever fired was on 21 April 1918, during the Great War, when Manfred von Richthofen, the famed "Red Baron" flying ace, was mortally wounded by a single .303 Mk 7 round."
I know that one of the problems facing those who try to figure out who shot vonR was that the same cartridge was used in rifles, airborne and ground based machine guns.
So, try setting it at 174 and see what you think... Hope this is helpful.
Hex