.600 Nitro Express

The .600 Nitro Express is a large-bore rimmed rifle cartridge the London gunmaker W. J. Jeffery & Co. developed around 1900 for hunting dangerous game, firing a 900-grain, roughly .620-inch bullet in one of three standard factory loadings that varied its muzzle velocity. Jeffery built its rifles for the round in four different break-open and falling-block actions, producing perhaps seventy in total; until the .700 Nitro Express arrived in 1988, it stood as the most powerful cartridge offered in a commercially available sporting rifle, and by one 2009 estimate only around a hundred rifles chambered for it had ever been made.

Its recoil is heavy enough that period rifles built for it typically weighed up to about 7 kg, and one British sniping officer who used a .600-chambered rifle during the First World War recorded that firing it from a prone position had broken a colleague’s collarbone. That wartime use came about because German snipers were operating from behind steel plates immune to standard .303 British rifle ammunition; the British War Office purchased a small number of large-bore sporting rifles, including four in .600 Nitro Express, and issued them to regiments to defeat those plates. Because it was too heavy to carry all day, the round also found a niche among professional big-game hunters as a backup weapon carried by a gun bearer for close-range use in thick cover.

All three published velocity figures come from secondary reference books (Frank Barnes’ Cartridges of the World and John Taylor’s African Rifles and Cartridges) rather than a clickable primary source, so they are recorded as estimated. The cartridge’s case and pressure dimensions, by contrast, come from C.I.P.’s own published standard and are recorded as verified.