This is an M61A1 20mm Vulcan Cannon as prepared for aircraft mounting. It is part of the "Gatling" family of externally powered guns. This is not a minigun (M134). This is not a chaingun. It is a Vulcan Cannon. Let there be no more confusion on the matter.
The M61 puts out 3,200 pounds of recoil force at 6,000 shots per minute.
The easiest way to distinguish between the A1 and A2 is the drum. On the A2 the drum is skeletonized and the internal feed rails are easily visible from the front.