eventually extended to a total of about 26 variations. The bolt thrust of the .303 British is relatively low compared to many other service rounds used in the early 20th century. Propellant The original .303 British service cartridge employed black powder as a propellant, and was adopted for the Lee–Metford rifle, which had rifling designed to lessen fouling from this propellant, which replaced the Martini-Henry rifle in 1888. Some Martini-Henrys were rebarrelled to use the new .303 as the "Martini–Metford" The Lee–Metford was used as a trial platform by the British Committee on Explosives to experiment with many different smokeless powders then coming to market, including Ballistite, Cordite, and Rifleite. Ballistite was a stick-type smokeless powder composed of soluble nitrocellulose and nitroglycerine. Cordite was a stick-type or 'chopped' smokeless gunpowder composed of nitroglycerine, gun-cotton, and mineral jelly, while Rifleite was a true nitrocellulose powder, composed of soluble and insoluble nitrocellulose, phenyl amidazobense, and volatiles similar to French smokeless powders. Unlike Cordite, Rifleite was a flake powder, and contained no nitroglycerine. Excessive wear of the shallow Metford rifling with all smokeless powders then available caused ordnance authorities to institute a new type of barrel rifling designed by the Royal Small Arms Factory at Enfield, to increase barrel life; the redesigned rifle introduced in 1895 as the Lee–Enfield. After extensive testing, the Committee on Explosives selected Cordite for use in the Mark II .303 British service cartridge. Projectile The initial .303 Mark I and Mk II service cartridges used a , round-nosed, copper-nickel full metal jacketed bullet with a lead core. After tests determined that the service bullet had too thin a jacket when used with cordite, the Mk II bullet was introduced, with a flat base and thicker copper-nickel jacket. Mark II – Mark VI The Mk II round-nosed bullet was found to be unsatisfactory when used in combat, particularly when compared to the "dum-dum" expanding bullet rounds issued in limited numbers in 1897 during the Chitral and Tirah expeditions of 1897–98 on the North West Frontier of India. This led to the 1898 introduction of the Cartridge S.A. ball .303 inch Cordite Mark III, basically the original 215-grain (13.9 g) bullet with the jacketing cut back to expose the lead in the nose. The Mk III load, however, was almost immediately withdrawn as a result of production issues leading to the introduction of the similar Mk IV hollow-point loading in