Leader Propulsion Systems has prototyped a "centrifuge gun" that spins up ball bearings and releases them at speeds of 300 meters per second, equivalent to a handgun. Inventor Charles St. George says that a large US defense contractor has signed on to further develop the weapon, appropriately named DREAD. From New Scientist:
He claims a fully developed DREAD gun would be quieter than a conventional gun, less prone to malfunction, and could contain more ammunition.Link to New Scientist article, Link to more background from Defense Review, Link to original Defense Review article including funny/scary video "commercial"
DREAD also releases its balls in extremely rapid succession, which allows it to unleash formidable firepower against a target. Promotional material for DREAD states: "Due to its extraordinary high rate of fire capability, it delivers its bullets 8.5 millimetres apart, thereby delivering more mass to the target than any other weapon."