W.J. Jeffery & Co
Place of origin
Semi-rimmed or rimless, bottleneck
The .303 Magnum is a bottleneck centerfire rifle cartridge developed by W.J. Jeffery & Co and introduced in 1919. It was produced in both semi-rimmed and rimless versions.
The cartridge was designed by Jeffery for target shooting, and was used for some time by the British Match Rifle Committee. The .303 Magnum's case capacity is the same as the .30-06 Springfield, although performance was considered to favour the .303 Magnum. The .303 Magnum had a brief life, only appearing in the Kynoch catalogue until 1930.
The .303 Magnum fires a 174 gr projectile at 2850 fps.