Weapons: Lightweight 7.62mm Machine-Guns


June 21, 2011:  The U.S. Army has ordered 3,053 of the new, lightweight, M-240L 7.62mm machine-guns, for $9,200 each. This model of the M-240 is 1.7 kg (3.75 pounds) lighter than the previous, M-240B. This was accomplished by using some lighter (titanium) components. Some other new components are also more durable. The reduction in weight makes a big difference for anyone carrying one of these up and down hills in Afghanistan for hours on end.

SOCOM (Special Operations Command) took a different approach. A decade ago they began using the Mk 48 7.62mm machine-guns. These are 8.2 kg (18.3 pound) weapons. That's lighter than the 10.1 kg (22.2 pound) M-240L or the current standard, 11.8 kg (26 pound), M240B. SOCOM troops need the light weight for commando operations. But that light weight comes at the expense of durability. The lighter components don't last as long. For example, the M240 bolt and receiver are both good for 100,000 rounds fired. But on the Mk 48, the bolt has to be replaced after 15,000 rounds and the receiver after 50,000. This was not a problem with the commandos, who made sure they had plenty of spares available, and kept track of the (approximate) number of rounds fired. Not so hard to do, you just have to pay attention.

The Mk 48 began as a scaled up 7.8 kg (17 pound) M249 (the standard 5.56mm) light machine-gun. The Mk 48 only weighs half a kilogram (about a pound) more, and troops always take their M249s with them. Of course, the 7.62mm ammo is heavier. Each 100 rounds of 7.62mm weighs nearly a kilogram (two pounds) more than 100 rounds of 5.56mm. But the Mk 48 is usually fired in short, six round, bursts. So a few hundred rounds will last a while.

The M-240L is just one of many new, lightweight, items being introduced in Afghanistan. New, and lighter boots, tools and body armor will lighten the infantryman's load by an average 13 pounds (5.9 kg). This is a big deal for grunts who spend hours marching and running around carrying 60-100 pounds of gear.