The .303 British was developed in 1887 and officially adopted in 1888 by the British Empire. Originally it was a black-powder cartridge that consisted of a 215-grain roundnose bullet with a cupronickel jacket propelled with 70 grains of black powder for a reported 1,850 fps velocity. As new powders were developed, including cordite and double base extruded powders, the velocity was increased to around 1,970 fps. Eventually bullets were improved with a 175-grain spitzer being pushed to 2,440 fps, which was the standard issue military load until the cartridge was retired. The British used this cartridge for around 70 years, through two world wars and countless engagements, replacing it in 1957 with the 7.62 NATO. Its popularity around the world is widespread, and with many surplus rifles available, almost all major ammunition companies offer loads.

As is often the case with cartridges having such a long history, the groove diameter of rifles can vary. In developing the accompanying data, Hornady bullets measuring .310 and .312 inch were used, with the best accuracy in an Enfield No. 4 MK1 being achieved with 150- and 174-grain, .312-inch bullets.

In duplicating the ballistics of factory loads from Federal, Remington and Winchester with 150- and 174-grain bullets, Accurate AAC-2520 powder gave outstanding results.

Many service rifles have been fired extensively, and have excess headspace, which can cause accuracy loss and can even be dangerous. If in question, have your rifle checked by a qualified gunsmith prior to firing it with any ammunition. Maximum industry pressure guidelines for the .303 British are currently established at 49,000 psi, and none of the accompanying data exceeds that figure.