.505 Gibbs
The .505 Gibbs cartridge was designed by George Gibbs in 1911. The cartridge was originally known as the .505 Rimless Nitro Express or simply as the .505 Rimless. C.I.P. refers to the cartridge as the 505 Mag. Gibbs in their publications. It is a .50 caliber (12.8 mm) rimless bottlenecked cartridge intended for magazine-fed rifles.
General information
The .505 Gibbs has a case capacity of 178 grains (11.5 g) of water. This cartridge was originally loaded with 90-grain (5.8 g) of cordite and 525-grain (34.0 g) bullet at 2,300 ft/s (700 m/s) for 6,166 ft·lbf (8,360 J) of kinetic energy. While the .505 Gibbs has a greater case capacity than most modern cartridges, it is loaded to lower pressures. The C.I.P. recommends a pressure standard of 2,700 bars (39,160 p.s.i.) for the cartridge. As .505 Gibbs was intended for hunting dangerous game in a tropical environment and due to the temperature sensitivity of cordite the lower pressures provided a greater safety and reliability margin.