http://www.wired.com/news/conflict/0,2100,46570,00.html
I suggest you read the whole thing but two quick quotes to give you an idea
In perhaps the most audacious upgrade of high-speed weaponry since the introduction of the Gatling Gun, Australian inventor Mike O'Dwyer has developed a machine gun that can fire bullets at a rate of 1 million rounds per minute.
DiscussJust how lethal? That depends on how many rounds you want to fire and how many barrels you want to put to use. In a test firing of 36 barrels, lashed together and firing full bore, the gun reduced a series of 15 wooden doors to toothpicks in just two-tenths of a second.