To correct this, the weak rolled brass cartridge was replaced by a stronger drawn brass version, and a longer loading lever was incorporated into the MK-IV to apply greater torque to operate the mechanism when fouled. These later variants were more reliable in battle, although it was not until smokeless nitro powders and copper-jacketed bullets were tried out in these rifles in the 1920s that accuracy and 100% reliability of cartridge case extraction was finally achieved by Birmingham ammunition makers (Kynoch). English hunters on various safaris, mainly in Africa, found the Martini using a cordite charge and a 500-grain full-metal-jacketed bullet effective in stopping large animals such as hippopotamus up to 80 yards away.