 As a result, the Lee–Enfield rifle was retained, and the .303 British cartridge (with the improved Mark VII loading) was kept in service.In 1938 the Mark VIIIz "streamline ammunition" round was approved to obtain greater range from the Vickers machine gun.The streamlined bullet was based on the 7.5×55mm Swiss GP11 projectiles and slightly longer and heavier than the Mk VII bullet at , the primary difference was the addition of a boat-tail at the end of the bullet and using of nitrocellulose smokeless powder as propellant in the case of the Mk VIIIz, giving a muzzle velocity of .