General Electric started it off back in the 1950s with the M-61 Vulcan; a six-barreled 20x102mm rotary cannon with rates of fire of 6000 to 6600 rounds per minute (rpm).
General Electric then developed the M-134 7.62x51mm (.308 Win.) "Minigun" with rates of fire of 1000-6000 rpm. Dillon Precision has improved upon the original M-134 by redesigning the feed and de-linker assemblies and reducing the maximum rate of fire to 4000 rpm resulting in a much more reliable weapon.
The XM-214 "Micro Minigun" was a scaled down version of the M-134 chambered in 5.56x45mm (.223 Rem.) with a continuously adjustable rate of fire of 400 to 10,000 rpm! A stepped trigger of 1000/6000/10,000 rpm was developed but the maximum rate was set at 6000 rpm. Fewer than 24 were built before the project was cancelled.
Other Gatling guns developed by General Electric are the M-197, a 3 barreled, lightweight version of the M-61. The M-197 is used on the Army's AH-1F and Marine AH-1W/Z Cobra. Rate of fire is 730+/50 rpm.
The GAU-12/A "Equalizer" is a 25x137mm cannon used in the USMC's Harrier II and USAF AC-130U Spooky. A variant, the GAU-22/A is to be used on the F-35.