The fighting in Iraq is taking a toll on the assault rifles and light machine-guns that do most of the shooting. So the U.S. Department of Defense has ordered another 50,881 M-4 assault rifles, at $1,042 each, and another M249 Squad Automatic Weapon (SAW) 5.56-mm light machine guns, at $667 each. The M-4 is a short barrel M-16, which makes it easier to use from inside a vehicle, or when fighting inside a building. The M249 is basically an M-16 design modified with a heavier (and easy to change) barrel, and the ability to use belted ammunition. The M249 provides most of the firepower for the infantry, with each fire team of 4-5 troops having one M249, over a thousand rounds of belted ammo and one or two additional barrels (when the M249 barrel gets overheated from firing too many rounds too quickly, a fresh one can be installed within seconds.) The U.S. Army wants a new design for their light machine-gun, partly because the M249 (introduced in the early 1980s) was wearing out. But the heavy use of M249s in Iraq and Afghanistan has resulted in a need for new weapons, before a new design can be agreed on and put into production.