These weapons typically fired the 7.62×39mm cartridge fired by the AK-47 series or the 5.56×45mm NATO standard cartridge first used in the AR-15/M-16 rifles. These very lightweight machineguns were designed for more sustained fire than normal infantry rifles, several hundred rounds worth of extended firing. They were similar in weight to an empty older light machine gun and several pounds lighter than mediums, but offered a much higher volume of fire due to their smaller caliber and lighter round; lower cartridge weight allows a greater total amount of ammunition to be carried by a gunner and/or other squad members carrying additional ammunition for the weapon. Many models were scaled-down medium caliber designs or heavier, longer-barrel versions of infantry standard Assault rifles. Examples include the FN Minimi, M249 (US designation of the FN Minimi) or the RPK.