.256 Gibbs Magnum

The .256 Gibbs Magnum is an obsolete rimless bottleneck centerfire rifle cartridge developed by George Gibbs of Bristol and introduced in 1913.

Overview
The .256 Gibbs Magnum was designed and introduced by George Gibbs in 1913 for use in their own Mauser style sporting rifles. The cartridge was created by reducing the neck of the 6.5×57mm Mauser by 2 mm.

The .256 Gibbs Magnum is very similar to, but not interchangeable with, the 6.5×55mm Swedish cartridge.

One famous user of the .256 Gibbs Magnum was Denis D. Lyell who used a rifle in this calibre for hunting in Africa.