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.303 British
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.303 British
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 rimmed tapered bottleneck centerfire 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.
It was first manufactured in Britain as a stop-gap black powder round put into service in December 1888 for the Lee–Metford rifle. From 1891 the cartridge used smokeless powder which had been the intention from the outset, but the decision on which smokeless powder to adopt had been delayed. It was the standard British and Commonwealth military cartridge for rifles and machine guns from 1889 until it was replaced by the 7.62×51mm NATO in the 1950s.
The .303 British has a 3.64 mL (56 gr 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.
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), 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).
According to official rulings of the Commission internationale permanente pour l'épreuve des armes à feu portatives (CIP), the .303 British can handle up to 3,650 bars (365.0 MPa; 52,940 psi) Pmax piezo pressure. In CIP-regulated countries every rifle cartridge combo has to be proofed at 125% of this maximum CIP pressure to certify for sale to consumers. This means that .303 British chambered arms in CIP-regulated countries are, as of 2023[update], proof tested at 4,562 bars (456.2 MPa; 66,170 psi) PE piezo pressure.
The Sporting Arms and Ammunition Manufacturers' Institute (SAAMI) maximum average pressure (MAP) for this cartridge is 49,000 psi (338 MPa) piezo pressure (45,000 CUP).
The measurement .303 inches (7.7 mm) is the nominal size of the bore measured between the lands which follows the older black powder nomenclature. Measured between the grooves, the nominal size of the bore is .311 inches (7.9 mm). Bores for many .303 military surplus rifles are often found ranging from around .309 to .318 inches (7.8–8.1 mm). Recommended bullet diameter for standard .303 British cartridges is .312 inches (7.9 mm).
During a service life of over 70 years with the British Commonwealth armed forces, the .303-inch (7.7 mm) cartridge in its ball pattern progressed through ten marks, eventually extending to about 26 variations. The bolt thrust of the .303 British is relatively low compared to many other service rounds used in the early 20th century.[citation needed]
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.303 British
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 rimmed tapered bottleneck centerfire 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.
It was first manufactured in Britain as a stop-gap black powder round put into service in December 1888 for the Lee–Metford rifle. From 1891 the cartridge used smokeless powder which had been the intention from the outset, but the decision on which smokeless powder to adopt had been delayed. It was the standard British and Commonwealth military cartridge for rifles and machine guns from 1889 until it was replaced by the 7.62×51mm NATO in the 1950s.
The .303 British has a 3.64 mL (56 gr 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.
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), 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).
According to official rulings of the Commission internationale permanente pour l'épreuve des armes à feu portatives (CIP), the .303 British can handle up to 3,650 bars (365.0 MPa; 52,940 psi) Pmax piezo pressure. In CIP-regulated countries every rifle cartridge combo has to be proofed at 125% of this maximum CIP pressure to certify for sale to consumers. This means that .303 British chambered arms in CIP-regulated countries are, as of 2023[update], proof tested at 4,562 bars (456.2 MPa; 66,170 psi) PE piezo pressure.
The Sporting Arms and Ammunition Manufacturers' Institute (SAAMI) maximum average pressure (MAP) for this cartridge is 49,000 psi (338 MPa) piezo pressure (45,000 CUP).
The measurement .303 inches (7.7 mm) is the nominal size of the bore measured between the lands which follows the older black powder nomenclature. Measured between the grooves, the nominal size of the bore is .311 inches (7.9 mm). Bores for many .303 military surplus rifles are often found ranging from around .309 to .318 inches (7.8–8.1 mm). Recommended bullet diameter for standard .303 British cartridges is .312 inches (7.9 mm).
During a service life of over 70 years with the British Commonwealth armed forces, the .303-inch (7.7 mm) cartridge in its ball pattern progressed through ten marks, eventually extending to about 26 variations. The bolt thrust of the .303 British is relatively low compared to many other service rounds used in the early 20th century.[citation needed]
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