The .303 British (designated as the 303 British by the C.I.P. C.I.P. TDCC datasheet 303 British and SAAMI ) or 7.7×56mmR, is a 0.303 inches calibre (with the bore diameter measured between the lands as is common practice in Europe) rimmed rifle cartridge first developed in Britain as a black-powder round put into service in December 1888 for the Lee–Metford rifle.