The military has been investing in several different kinds of fancy bullets over the last few years, from bullets with smart microgrenades to bullets with fins that can steer to their target. And in order to be able to use the right bullet for the right task, the Army wants a gun that can custom-select ammo at hundreds of rounds per minute.
With firearms designed to be used by individuals, switching ammunition types usually isn't much of a problem, since you can always just unload your weapon and then reload it with something else. But, when you've got one of those giant airplane or helicopter-sized machine guns, changing from one type of ammunition to another generally involves doing something complicated like landing first. To avoid this, aircraft are often-preloaded with a randomly festive assortment of whatever they might find useful, which means (as anyone who's ever gotten a bag of jellybeans understands) that you spend a lot of the time regretting that you didn't just get a single flavor that you knew you'd like.
What the Army wants instead is a system that's able to select from a menu of different rounds (Just like Judge Dredd! -Ed), and then feed those rounds into a chain gun at up to 300 rounds per minute, probably debuting in attack helicopters like the Apache. While the increased complexity of such a system would cut the number of rounds that you'd be able to carry by a third, the idea is that this would be compensated for by "improved lethality, reduced collateral damage, improved vehicle performance due to reduced ammunition carriage, [and] efficient use of expensive smart rounds."
Once a system like this is up and running, it could also be used to rapidly sort and deploy anything else that's about the same size and shape as a bullet. This would be good for applications in medical labs, or even spitting out high-speed food and water modules in emergency supply centers. Just make sure you bring a catcher's mitt. And body armor. And don't forget to duck.
Via Danger Room