.303 British

7.7×56mmR or .303 British is the British battle rifle cartridge. Originally developed for Lee-Metford rifle with black powder load in mind, soon it was reworked to use smokeles powder for Lee-Enfield rifle. Compared to many of its contemporaries, .303 is notably less powerful, and to put things in to perspective, it's notably less powerful than 7.62x51. So, while it is still in use, it's a rather limited use.

Ammunition types

 * Mark I Ball: 215-grain lead/antimony cored bullet with cupro-nickel envelope, approved on 3 November 1891.
 * Mark II Ball: The bullet differed from the previous mark by the inclusion of 0.5% iron in the cupro-nickel envelope and slightly higher muzzle velocity. Approved in July 1893.
 * Mark III Ball HP: Round nosed bullet with a cupro-nickel envelope and lead/antimony core. The nose had a hollow point. Introduced in October 1897, but soon deemed as unsuccessful design, despite its infamous terminal performance. Ever heard about Dum-Dum bullets? That's one of them.
 * Mark IV Ball HP: Improved expanding bullet with pure lead core. Approved in February 1898.
 * Mark V Ball HP: Core was changed back to lead antimony. Approved in October 1899, and briefly became standard military issue round, until concerns about the legality of this and the previous Mark under the terms of the St.Petersburg Declaration and the Hague Convention led to manufacture being stopped after 1900, putting an end to Dum-Dums and military expanding rounds as a whole.
 * Mark VI Ball: Slight imrovement over Mark II, this cartridge had a round nosed 215 grain bullet but with a thinner cupro-nickel envelope to increase lethality. The core was an alloy of 98/2% lead antimony. Approved in October 1904.
 * Mark VII Ball: New high-velocity spitzer 174-grain bullet.Approved in November 1910.
 * Mark VIIZ Ball: 175-grain bullet with refined aerodynamics and hotter load, primarily used for long range machine gun fire. Approved in January 1938.
 * Mark VIIS Ball: The Mark VIIS was based on the normal Mark VII ball bullet but with the aluminium tip replaced by one of steel, slightly improving penetration. Approved in December 1915.
 * Mark VIIP AP: 174-grain bullet had a cupro-nickel envelope with a heeled steel core enclosed in a lead sleeve. Approved in November 1916.
 * Mark VIIZ AP: The bullet was made from solid copper rod, bored out to receive a steel core weighing 65 to 70 grains. Total bullet weight was 155 grains. For proof, 60% of bullets had to penetrate a 8mm plate at 175 yards and 80% had to penetrate a 7mm plate at 300 yards. Approved in August 1916.
 * Mark VIIW AP: The bullet had an envelope of cupro-nickel clad steel or gilding metal clad steel with a steel core in a lead sheath. It had one cannelure and weighed 174 grains, the core weighing 93 grains. For proof, 70% of bullets had to penetrate a 10mm plate at 100 yards range. Approved in November 1917.
 * Mark I Incendiary: Buckingham incendiary bullet filled with yellow phosphorus.
 * Mark II Incendiary: Improved Buckingham bullet filled with 10 grains of phosphorus and aluminium powder.
 * Mark IIZ Incendiary: Mark II round with nitrocellulose powder load.
 * Mark IIIZ Incendiary: Further refined Buckingham design filled with 14.5 grains of phosphorus and aluminium powder. Approved in July 1917.
 * Mark VII Incendiary: De Wilde incendiary bullet filled with 7 grains of SR 365 composition, containing barium nitrate which ignited on impact with the target. Approved in late 1939.
 * Mark VIIY: Pomeroy explosive bullet had a cupro-nickel envelope with a lead antimony core into which was inserted a copper warhead. This was open at the rear end and the nose had a small hole in the front. The warhead protruded from the envelope ans was filled with the explosive composition sealed at the rear end with a millboard disc. The bullet weighed about 155 grains and had a single cannelure. The composition was a dough of 73% nitroglycerine and 27% kieselguhr with a total weight of 15 grains. Approved in August 1916.
 * Mark I RTS: Threfall explosive bullet contained nitroglycerine in sawdust and the main composition in the lower part of the bullet was white phosphorus. Approved in late 1917.
 * Mark I RTT: Improved Threfall bullet had a cupro-nickel envelope, open at the nose with a copper warhead containing nitroglycerine inserted like the RTS Mark I. below this was another copper container containing 4 grains of a mixture of Kieselguhr dynamite and lead azide. The main composition was in the rear of the envelope and was 7 grains of PETN above 25 grains of white phosphorus. Not formally approved.
 * W Mark I AP: Post-WW1 158-grain steel-core armor-piercing load.
 * W Mark IZ AP: Improved version
 * W Mark ITP AP: Experimental "tank-piercing" load wih tungsten core.
 * 215C Ball: All-copper 215-grain round.
 * 215GHP HP: Modern version of 215-grain hollow-points.
 * Scott Duplex: "Double-whammy" load.
 * Greener Tripleball: Experimental triplex load.
 * Kynoch Triplex: Competing triplex load.