The Lee-Enfield rifle was derived from the earlier Lee-Metford, a mechanically similar black powder rifle, which combined James Paris Lee's rear-locking bolt system with a barrel featuring rifling designed by William Ellis Metford. The Lee action cocked the striker on the closing stroke of the bolt, making the initial opening much faster and easier compared to the "cock on opening" of the Mauser design. The rear-mounted lugs place the operating handle much closer to the operator, over the trigger, making it quicker to operate than traditional designs like the Mauser. The rifle was also equipped with a detachable sheet-steel, 10-round, double-column magazine, a very modern development in its day. Originally, the concept of a detachable magazine was opposed in some British Army circles, as some feared that the private soldier might be likely to lose the magazine during field campaigns. Early models of the Lee-Metford and Lee-Enfield even used a short length of chain to secure the magazine to the rifle.
The fast-operating Lee bolt-action and large magazine capacity enabled a well-trained rifleman to fire 20 to 30 aimed rounds a minute, making the Lee-Enfield the fastest military bolt-action rifle of the day. The current world record for aimed bolt-action fire was set in 1914 by a musketry instructor in the British Army—Sergeant Instructor Snoxall—who placed 38 rounds into a 12 inch wide target at 300 yards (270 m) in one minute. Some straight-pull bolt-action rifles were thought faster, but lacked the simplicity, reliability, and generous magazine capacity of the Lee-Enfield. First World War accounts tell of British troops repelling German attackers who subsequently reported that they had encountered machine guns, when in fact it was simply a group of trained riflemen armed with SMLE Mk III rifles.
Standard Mk VII .303 inch cartridge for Lee-Enfield rifleThe Lee-Enfield was adapted to fire the .303 British service cartridge, a rimmed, high-powered rifle round. Experiments with smokeless powder in the existing Lee-Metford cartridge seemed at first to be a simple upgrade, but the greater heat and pressure generated by the new smokeless powder wore away the shallow, rounded, Metford rifling after approximately 6000 rounds. Replacing this with a new square-shaped rifling system designed at the Royal Small Arms Factory (RSAF) Enfield solved the problem, and the Lee-Enfield was born.