some Colt M1911 pistols chambered in .455 Auto purchased by the Royal Navy. Although not a standard sidearm or a standard service cartridge, a few Colt M1911 "British service models" chambered in .455 Auto were sold commercially to British navy and army officers through outfitters. The service ammunition came packed in seven-round boxes stamped "not for revolvers" to prevent confusion. .476 Enfield Despite the apparent difference in caliber name, .476 Enfield was quite similar to the .455 Webley. The .476 had a shorter case than the .455 Mark I and could be fired in weapons regulated and marked as safe for the caliber, such as the Webley "WG Army" model. This had a cylinder that was long enough to accommodate the significantly longer cartridge in which the bullet swelled out to .476" beyond the case. It would not chamber in any government-issue .455 Webley Marks I–VI. The .450 Adams (1868), .476 Enfield (1881), and .455 Webley Mk.I (1891) British service cartridges all featured a case diameter of .476 inch [12.09mm]. See also Table of handgun and rifle cartridges Notes References Barnes, Frank C., ed. by John T. Amber. ".476 Eley/.476 Enfield Mk-3", in Cartridges of the World, pp. 175 & 178. Northfield, IL: DBI Books, 1972. . Maze, Robert J. Howdah to High Power. Tucson, AZ: Excalibur Publications, 2002. . Wilson, R. K. Textbook of Automatic Pistols, p. 228. Plantersville, SC: Small Arms Technical Publishing Company, 1943. External links "Those Confusing .455s" by Chris Punnett—Additional information on the .455 Webley cartridge Military cartridges Pistol and rifle cartridges British firearm cartridges Rimmed cartridges