.303 Magnum

The .303  is an arguably obsolete but capable medium bore rifle cartridge.

Overview
The .303 Magnum was a bottlenecked centerfire rifle cartridge that was produced in both semi-rimmed and rimless versions. The cartridge fired a projectile of 174 gr at 2850 ft/s. The cartridge's case capacity was the same as the .30-06 Springfield, although performance was considered to favour the .303 Magnum.

The .303 Magnum was developed by W.J. Jeffery & Co by necking up the experimental .276 Enfield to .312 in, it was introduced in 1919 for target shooting and was used for some time by the British Match Rifle Committee. The cartridge had a brief life, only appearing in the Kynoch catalogue until 1930 and it appears to have become obsolete by 1932.