The .455 Webley Mk.I ammunition was adopted by British army in 1887. With introduction of the cordite propellant this round was changed to .455 Mk.II with slightly longer case, which was also used for latter versions (Mk.III to Mk.V), which featured different bullets. All .455 revolver ammunition was officially declared obsolete by British military in around 1950. Some manufacturers still produce this ammunition for older guns, although no new guns were made for these loadings for quite some time.
Designation Manufacturer Bullet weight, g Muzzle velocity, m/s Muzzle energy, J Comments
.455 Mk.I 17.7 213 390 original black powder load
.455 Mk.II 17.2 177 268 original cordite loading of WW1 era
.455 Mk.II Fiocci 16.9 259 566 modern commercial loading