The FN MAG (Mitrailleuse d'Appui General or General Purpose Machinegun), was designed by Fabrique Nationale in the 1950's. It is a gas operated, belt fed, air cooled automatic weapon. It uses the long piston stroke gas system with the gas regulator, located below the barrel. The bolt is locked using a swinging shoulder that engages the cut in the floor of the receiver. The air-cooled barrel is quick-detachable, with the carrying handle attached to it to help handling of the hot barrel. A regular belt for the FN MAG comes in a box of 220, and one in five rounds is a tracer. The receiver is made from steel stampings. The FN MAG is used by commonwealth countries such as the UK L7A2 and Canadian C6 GPMG.