.303 inch British

.303 British (7.7×56mm Rimmed)
Left to right: .303 British, 6.5×50mmSR Arisaka and .30-06 Springfield soft point ammunition
Type	Rifle
Place of origin	United Kingdom
Service history
In service	1889–present
Used by	United Kingdom and many other countries
Wars	Second Boer War Boxer Rebellion World War I Various Colonial conflicts Irish War of Independence Irish Civil War World War II Indonesian National Revolution Indo-Pakistani Wars Greek Civil War Malayan Emergency French Indochina War Korean War Arab-Israeli War Suez Crisis Mau Mau Uprising Sino-Indian War Bangladesh Liberation War Soviet invasion of Afghanistan Nepalese Civil War Afghanistan conflict
Production history
Produced	1889–present
Specifications
Case type	Rimmed, bottleneck
Bullet diameter	7.92 mm (0.312 in)
Neck diameter	8.64 mm (0.340 in)
Shoulder diameter	10.19 mm (0.401 in)
Base diameter	11.68 mm (0.460 in)
Rim diameter	13.72 mm (0.540 in)
Rim thickness	1.63 mm (0.064 in)
Case length	56.44 mm (2.222 in)
Overall length	78.11 mm (3.075 in)
Case capacity	3.64 cm3 (56.2 gr H2O)
Rifling twist	254 mm (1-10 in)
Primer type	Large rifle
Maximum pressure (C.I.P.)	365.00 MPa (52,939 psi)
Maximum pressure (SAAMI)	337.84 MPa (49,000 psi)
Maximum CUP	45,000 CUP
Ballistic performance
Bullet mass/type Velocity Energy 150 gr (10 g) SP 844 m/s (2,770 ft/s) 3,463 J (2,554 ft·lbf) 174 gr (11 g) HPBT 761 m/s (2,500 ft/s) 3,265 J (2,408 ft·lbf) 180 gr (12 g) SP 783 m/s (2,570 ft/s) 3,574 J (2,636 ft·lbf)
Test barrel length: 24 Source(s): Accurate Powder

The .303 British (designated as the 303 British by the C.I.P. and SAAMI) or 7.7×56mmR, is a .303-inch (7.7 mm) 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. In 1891 the cartridge was adapted to use smokeless powder. It was the standard British and Commonwealth military cartridge from 1889 until the 1950s when it was replaced by the 7.62×51mm NATO.

The .303 British has 3.64 ml (56 grains H₂O) cartridge case capacity. The pronounced tapering exterior shape of the case was designed to promote reliable case feeding and extraction in bolt action rifles and machine guns alike, under challenging conditions.

.303 British maximum C.I.P. cartridge dimensions. All sizes in millimeters (mm).

Americans would define the shoulder angle at alpha/2 ≈ 17 degrees. The common rifling twist rate for this cartridge is 254 mm (10.0 in) 10 in), 5 grooves, Ø lands = 7.70 millimetres (0.303 in), Ø grooves = 7.92 millimetres (0.312 in), land width = 2.12 millimetres (0.083 in) and the primer type is Berdan or Boxer (in large rifle size).