The GA GAU-8 AVENGER GATLING GUN mounted in the A-10 Warthog.
They actually built the aircraft for the gun. Not the gun for the aircraft.
This will give you some idea of the weapon's size.
The gun shoots at a rate of 4200 rounds per minute. Yes, four thousand. Pilots typically shoot either one- or two-second burst which set loose 70 to 150 rounds. The system is optimized for shooting at 4,000 feet.
Each of those seven barrels is 112" long. That's almost ten feet. The entire gun is 19-1/2 feet long.
A comparison of shell sizes to the 30 mm round.
It doesn't eject the empty shells but runs them back into the storage drum. There's just so dang many flying out, they felt it might damage the aircraft.
I don't know why I go to this trouble. No one ever answers and if they do it's just some negative comment.