Colt is manufacturing functioning replica of the 1877 Bulldog Gatling Gun.
The gun fires the .45-70 cartridges at a rate up to 800 rounds per minutes (based on how fast you can spin the crank). The gun weighs around 250 lbs.
Colt brought it out to the media shoot day at SHOT 2012
The guys over at the Armory Blog got the chance to fire this gun a few times.
Pretty cool to see a gun like this in todays market.