.303 British (7.7×56mm Rimmed)
6.5x50mm Japanese with .303 British & .30-06.JPG
Left to right: .303 British, 6.5×50mmSR Arisaka and .30-06 Springfield soft point ammunition
Place of originUnited Kingdom
Service history
In service1889–present
Used byUnited Kingdom and many other countries
Production history
Case typeRimmed, bottleneck
Bullet diameter7.92 mm (0.312 in)
Neck diameter8.64 mm (0.340 in)
Shoulder diameter10.19 mm (0.401 in)
Base diameter11.68 mm (0.460 in)
Rim diameter13.72 mm (0.540 in)
Rim thickness1.63 mm (0.064 in)
Case length56.44 mm (2.222 in)
Overall length78.11 mm (3.075 in)
Case capacity3.64 cm3 (56.2 gr H2O)
Rifling twist254 mm (1-10 in)
Primer typeLarge rifle
Maximum pressure (C.I.P.)365.00 MPa (52,939 psi)
Maximum pressure (SAAMI)337.84 MPa (49,000 psi)
Maximum CUP45,000 CUP
Ballistic performance
C.I.P.[2] and SAAMI[3]) 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) rimmedriflecartridge 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.[4] It was the standard British and Commonwealth military cartridge from 1889 until the 1950s when it was replaced by the 7.62×51mm NATO.[2]

Cartridge dimensions

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.jpg

.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).

According to the official C.I.P. (Commission Internationale Permanente pour l'Epreuve des Armes à Feu Portatives) rulings the .303 British can handle up to 365.00 MPa (52,939 psi) Pmax piezo pressure. In C.I.P. regulated countries every rifle cartridge combo has to be proofed at 125% of this maximum C.I.P. pressure to certify for sale to consumers.[2] This means that .303 British chambered arms in C.I.P. regulated countries are currently (2014) proof tested at 456.00 MPa (66,137 psi) PE piezo pressure.

The SAAMI (Sporting Arms and Ammunition Manufacturers' Institute) Maximum Average Pressure (MAP) for this cartridge is 49,000 psi (337.84 MPa) piezo pressure (45,000 CUP).[5]

The measurement .303-inch (7.70 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-inch (7.90 mm). Bores for many .303 military surplus rifles are often found ranging from around .309-inch (7.85 mm) up to .318-inch (8.08 mm). Recommended bullet diameter for standard .303 British cartridges is .312-inch (7.92 mm).[6]

Military use

History and development

History and development

During a service life of over 70 years with the British Commonwealth armed forces the .303-inch cartridge in its ball pattern progressed through ten marks which eventually extended to a total of about 26 variations.[7] The bolt thrust of the .303 British is relatively low compared to many other service rounds used in the early 20th century.


The original .303 British service cartridge employed black powder as a propellant, and was adopted for the Lee–Metford rifle, which had rifling designed to lessen fouling from this propellant. The Lee–Metford was used as a trial platform by

The original .303 British service cartridge employed black powder as a propellant, and was adopted for the Lee–Metford rifle, which had rifling designed to lessen fouling from this propellant. The Lee–Metford was used as a trial platform by the British Committee on Explosives to experiment with many different smokeless powders then coming to market, including Ballistite, Cordite, and Rifleite.[8][9][10] Ballistite was a stick-type smokeless powder composed of soluble nitrocellulose and nitroglycerine.[10] Cordite was a stick-type or 'chopped' smokeless gunpowder composed of nitroglycerine, gun-cotton, and mineral jelly, while Rifleite was a true nitrocellulose powder, composed of soluble and insoluble nitrocellulose, phenyl amidazobense, and volatiles similar to French smokeless powders.[9][10] Unlike Cordite, Rifleite was a flake powder, and contained no nitroglycerine.[10] Excessive wear of the shallow Lee–Metford rifling with all smokeless powders then available caused ordnance authorities to institute a new type of barrel rifling designed by the RSAF, Enfield, to increase barrel life; the rifle was referred to thereafter as the Lee–Enfield.[8] After extensive testing, the Committee on Explosives selected Cordite for use in the Mark II .303 British service cartridge.[8]


The initial .303 Mark I and Mk II service cartridges employed a 215-grain, round-nosed, copper-nickel full-metal-jacketed bullet with a lead core. After tests determined that the service bullet had too thin a jacket when used with cordite, the Mk II bullet was introduced, with a flat base and thicker copper-nickel jacket.[11]

Mark II – Mark VI

The Au

The Australian movie Breaker Morant (film) features a famous popular culture reference to the .303. It tells the story of Harry “Breaker” Morant who served in the British Army during the Second Boer War and was court martialled for the murder of Boer prisoners of war. When asked by the court what rule of war authorized these killings, Morant replied, “Rule 303,” referring to the Lee Enfield .303 rifle, meaning that was all the authority he needed. Morant was found guilty and was executed by a firing squad.[21][22]

Mark VIIIzIn 1938 the Mark VIIIz "streamline ammunition" round was approved to obtain greater range from the Vickers machine gun.[23] The streamlined bullet was based on the 7.5×55mm Swiss GP11 projectiles and slightly longer and heavier than the Mk VII bullet at 175 gr (11.34 g), the primary difference was the addition of a boat-tail at the end of the bullet and using 37 to 41 gr (2.40 to 2.66 g) of nitrocellulose smokeless powder as propellant in the case of the Mk VIIIz, giving a muzzle velocity of 2,525 ft/s (770 m/s). As a result, the chamber pressure was higher, at 40,000 to 42,000 psi (275.8 to 289.6 MPa), depending upon loading, compared to the 39,000 psi (268.9 MPa) of the Mark VII(z) round.[[24][25] The Mark VIIIz streamline ammunition had a maximum range of approximately 4,500 yd (4,115 m).[26] Mk VIIIz ammunition was described as being for "All suitably-sighted .303-inch small arms and machine guns" – rifles and Bren guns were proofed at 50,000 psi (344.7 MPa) – but caused significant bore erosion in weapons formerly using Mk VII ammunition, ascribed to the channelling effect of the boat-tail projectile. As a result, it was prohibited from general use with rifles and light machine guns except when low flash was important and in emergencies[27] As a consequence of the official prohibition, ordnance personnel reported that every man that could get his hands on Mk VIIIz ammunition promptly used it in his own rifle.[23]

Tracer, armour-piercing and incendiary

cordite propellant used in Mk 8 cartridges, which burns at a much higher temperature than nitrocellulose, there is increased barrel erosion. The cumulative effects of firing Mk 8 ammunition through rifles were known during the Second World War, and British riflemen were ordered to avoid using it, except in emergencies. The best general-purpose ammunition for any .303 military rifle is the Mark 7 design because it provides the best combination of accuracy and stopping power.[citation needed]

Japan produced a number of machine guns that were direct copies of the British Lewis (Japanese Type 92 machine gun) and Vickers machine guns including the ammunition. These were primarily used in Navy aircraft. The 7.7mm cartridge used by the Japanese versions of the British guns is a direct copy of the .303 British (7.7×56mmR) rimmed cartridge and is distinctly different from the 7.7×58mm Arisaka rimless and 7.7×58mm Type 92 semi-rimmed cartridges used in other Japanese machine guns and rifles.[32]

  • Ball: 174 grains (11.3 g). Cupro-Nickel jacket with a composite aluminium/lead core. Black primer.
  • Armour-Piercing.: Brass jacket with a steel core. White primer.
  • Tracer: 130 grains (8.4 g). Cupro-Nickel jacket with a lead core. Red primer.
  • Incendiary: 133 grains (8.6 g). Brass jacket with white phosphorus and lead core. Green primer.
  • H.E.: Copper jacket with a PETN and lead core. Purple primer.

Note: standard Japanese ball ammunition was very similar to the British Mk 7 cartridge. The two had identical bullet weights and a "tail-heavy" design, as can be seen in the cut-away diagram.

Civilian use

The .303 cartridge has seen much sporting use with surplus military rifles, especially in Australia, Canada, New Zealand and to a lesser extent, in the United States and South Africa. In Canada, it was found to be adequate for any game except the great bears. In Australia, it was common for military rifles to be re-barreled in .303/25 and .303/22. However the .303 round still retains a considerable following as a game cartridge for all game species, especially Sambar deer in wooded country. A recent change.org petition seeking Lithgow Arms to chamber the LA102 centerfires rifle in .303 as a special edition release has attracted considerable attention both in Australia and worldwide. In South Africa .303 British Lee–Enfield rifles captured by the Boers during the Boer War were adapted for sporting purposes and became popular with many hunters of non-dangerous game, being regarded as adequate for anything from the relatively small impala, to the massive eland and kudu.[33]

Commercial ammunition and reloading