.303 cartridge

The .303 British (7.7 x 56 mm R) is a rifle and machine gun cartridge first developed in Britain in the 1880s as a blackpowder round, later adapted to use cordite and then propellant. It was the standard British and Commonwealth cartridge from 1889 until the 1950s, when it was replaced by the .223 NATO in most roles. It is a rimmed cartridge and is therefore not entirely suitable for use in modern automatic weapons, but remains popular due to the large number of surplus military rifles chambered for the round which have been released to the civilian market, some of which have subsequently been modified for sport.

History

The Cartridge, S.A., Ball, Magazine Rifle, Mark I Solid Case, .303inch was first introduced with the Lee-Metford rifle in 1889. In its original form, the round was a 215 grain (13.9 g) round-nosed cupro-nickel jacketed bullet propelled by 71.5 grains (4.63 g) of RFG2 Blackpowder, giving it a muzzle velocity of 1830 feet per second (560 m/s) and a chamber pressure of about 19 short tons force per square inch (260 MPa). Blackpowder is not very dense, and the charge had to be pressed into a solid pellet in order to fit inside the round. The rimmed cartridge made it easy to extract spent rounds from the chamber, although it did make them somewhat harder to stack in a magazine because the protruding rims would cause a jam if they were loaded incorrectly due to a double feed—that is the rim of the cartridge being fed by the bolt snagging the subsequent cartridge rim.

Cordite was used as a propellant from 1891 and the first adopted cordite cartridge, the Cartridge S.A. Ball, Magazine Rifle Cordite Mark 1, used the same bullet but delivered 1970 ft/s (600 m/s) at a chamber pressure of about 35,000 pounds-force per square inch (240 MPa). Small changes to the bullet jacket resulted in the Mark II of both the black powder and cordite versions, the Mark 2 and Mark 2.C respectively.

Nitrocellulose was first used as a propellant in 1894, but the higher temperatures and chemical activity was enough to make it unsuitable for use in the Lee-Metford, and the newer Lee-Enfield was introduced to address these problems. Although not officially adopted until 1916, nitrocelulose rounds were widely used during World War I, although cordited-loaded rounds were still produced for use in the tropics, where it was considered to be somewhat more stable.

The round nose bullet was found to be less than satisfying in combat, notably when compared to the Dum Dum rounds issued in limited numbers in 1897 during the Chitral and Tirah expeditions of 1897/98 on the North West Frontier of India. This led to the introduction of the Cartridge S.A. Ball .303 inch Cordite Mark 3, basically the original 215 grain (13.9 g) bullet with the jacketing "cut back" to expose the lead in the nose. Similar hollow point bullets were used in the Mark 4 and 5 rounds, the primary production versions. These soft nosed and hollow pointed bullets were later outlawed in the St Petersburg Declaration and the Hague Convention, and in 1903 they were withdrawn from active service and were afterwards to be used for target practice until stocks ran out. To replace them the Mark 6 round was introduced in 1904, using a round nose bullet similar to the Mark 2 but with a thinner jacket. It was generally agreed to be unsatisfactory.

In 1905 Mauser changed bullet design completely with the introduction of their "spitzer" rounds, the first of the classic design now referred to universally as "bullet shaped". In addition to being pointed, the round was also much lighter in order to deliver a higher muzzle velocity. It was found that as velocity increased the bullets suddenly became much more deadly, an effect later explained by cavitation when the round hit.

The British took the opportunity to replace their Mark 6 rounds with the new Mark 7, using a 174 grain (11.3 g) pointed bullet that gave a muzzle velocity of 2440 ft/s (740 m/s). In fact the Mark 7 was considerably different than earlier designs, or the spitzer for that matter. In order to lower the weight they made the front 1/3rd of the interior of the bullet out of aluminium instead of lead. While similar weight savings could have been had by using a single lighter material, such as steel, the design was deliberate in order to make the bullet "tail heavy". When flying through air the stability of the bullet was marginal, but when it rapidly decelerated when hitting a target, the heavier lead base wanted to "swap ends", causing the bullet to tumble and greatly increase damage. The Mark 7 round remained the standard for the remainder of the .303 service life.

In 1938 the Mark 8 round was approved to obtain greater range from the Bren

Specifications

• Maximum length:
  • Case: 2.222 in (56.44 mm)
  • Overall: 3.04 in (77.2 mm)
• Case trim length: 2.212 in (56.18 mm)
• Primer type: Large rifle.
  • Boxer or Berdan primed cases may be encountered.
• Rim thickness: 0.064 in (1.63 mm)
• Rim diameter: 0.540 in (13.7 mm)
• Case capacity (water): 55.7 gr (3.61 g)
• SAAMI maximum pressure standard: 45,000 CUP (310 MPa) / 49000 lbf/in² (338 MPa)

See also

• List of rifle cartridges

External links

• African Hunter (http://www.cybertorpedo.com/africanhunter/classcart/303british_01.htm)
• Sniper Central (http://www.snipercentral.com/303.htm)