The .600 Nitro Express is a large bore Nitro Express rifle cartridge developed by W.J. Jeffery & Co for the purpose of hunting large game such as elephant. Design The .600 Nitro Express is a slightly tapered walled, rimmed, centerfire rifle cartridge designed for use in single-shot and double rifles. The cartridge fires a diameter, projectile with three powder loadings: the standard being of cordite at a muzzle velocity of ; a loading which generates a muzzle velocity of ; and a loading which generates a muzzle velocity of . Because of the recoil forces generated by this cartridge, rifles chambered in it typically weigh up to . Dimensions History The .600 Nitro Express was developed by London gunmakers W.J. Jeffery & Co. Sources vary about the date of its introduction, although it would seem in 1900 the first .600 Nitro Express rifle was produced by W.J. Jeffery & Co, a double barrelled hammer rifle. Jefferys produced around seventy rifles in .600 Nitro Express in four actions, double barrelled hammer break-open, single barrelled break-open, falling block and double barrelled break-open with and without ejectors. Until the introduction of the .700 Nitro Express in 1988, the .600 Nitro Express was the most powerful commercially available hunting rifle cartridge in the world. Aside from W.J. Jeffery & Co, several gunmakers have and continue to offer rifles chambering this .600 Nitro Express, although in 2009 it was estimated by Holland & Holland that only around one hundred .600 Nitro Express rifles had ever been produced to that time. WWI service In 1914 and early 1915, German snipers were engaging British Army positions with impunity from behind steel plates that were impervious to .303 British ball ammunition. In an attempt to counter this threat, the British War Office purchased sixty-two large-bore sporting rifles from British rifle makers, including four .600 Nitro Express rifles, which were issued to regiments. These large-bore rifles proved very effective against the steel plates used by the Germans. In his book, Sniping in France 1914-18, Major H. Hesketh-Prichard, DSO, MC stated they "pierced them like butter". Stuart Cloete, sniping officer for the King's Own Yorkshire Light Infantry, stated "We used a heavy sporting rifle - a .600 Express. These had been donated to the army by big game hunters and when we hit a plate we stove it right in. But it had to be fired standing or from a