View Here : M249 Machine Gun
The M249 is a belt-fed automatic machine gun, which means that the ammunition for the weapon comes from a belt, rather than a box (As seen in weapons such as the M4A1 assault rifle, M9 pistol, and MP5 submachine gun) or integral magazine (as seen in bolt-action, single-shot weapons and most shotguns).
"Absolutely great gun. The M249 is intimidating and great SAW weapon. For those who plan on using the box clip regularly, I would suggest making sure to having quality, new batteries for it.