Developed during the Vietnam War, the MK 19 belt-fed grenade launcher is one of the most destructive man-portable military weapons. It fires 40 mm grenades 2419 yards at a rate of 60 per minute!
This grenade launcher comes with belts of 32 or 48 that weigh 48 and 60 pounds, respectively. The US army plans to introduce an upgraded package soon.
Check out this video that deminstrates how effective this weapon can be.