I’m sure you’re all familiar with the M-134 Minigun that was used in Vietnam on aircraft – a 7.62 NATO rotary gun with a 3000RPM rate of fire. But have you seen its competitor, the EX-17 Heligun?
The Heligun was developed by Hughes Aircraft as part of a complete package for the OV-6 recon helicopter. It offered a number of significant advantages over the Minigun – it was half the weight, self-powered (not electrically driven), and had a mind-boggling 6000RPM firing rate. Ultimately, it was note adopted because the reliability (mean time between stoppages) couldn’t quite be brought up to par, and Army officials decided that it didn’t offer enough improvement over the already adopted M134 Minigun to be worth the switch.
We have available a complete (~120 pages) report on the development of the EX-17 written by Hughes in 1966, including comparison to the M134, analysis of stoppages, and large schematic drawing of the Heligun (click to download in PDF format):