.303 British
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The .303 British or 7.7×56mmR, is a .303-inch calibre rimmed tapered rifle cartridge. The .303 inch bore diameter is measured between rifling lands as is the common practice in Europe which follows the traditional black powder convention. Wikipedia
Bullet diameter: 7.92 mm (0.312 in)
Case capacity: 3.64 cm3 (56.2 gr H2O)
In service: 1889–present
Maximum CUP: 45,000 CUP
Maximum pressure (C.I.P.): 365.00 MPa (52,939 psi)
Place of origin: United Kingdom