to . The .450 Dakota fires a bullet at . .450 Rigby The .450 Rigby was designed by Paul Roberts of John Rigby & Company. The cartridge was designed to fire a bullet at . .510 Whisper The .510 Whisper is a subsonic rifle cartridge developed by SSK Industries for use in suppressed rifles, with the noise similar to that of a .22 Short.[2] It fires a .51-caliber bullet weighing at roughly . See also .416 Remington Magnum .416 Ruger .416 Weatherby Magnum .450 Rigby .510 Whisper 10 mm caliber List of rifle cartridges Table of handgun and rifle cartridges References John Rigby & Co. (Gunmakers) Ltd. London, England (recent website) John Rigby (Gunmakers) Ltd. London, England (archived website) TDCCs (cartridge dimension and specs tables) - info, database query, downloads (C.I.P.) British firearm cartridges John Rigby & Co cartridges Pistol and rifle cartridges