Airmen conducting pre-flight inspections and prepping for 20mm munitions load onto F-15 fighters’ M61 Vulcan rotary cannon during training exercise Beverly High.

The M61 Vulcan is a hydraulically or pneumatically driven, six-barrel, air-cooled, electrically fired gatling gun which fires 20 mm rounds at an extremely high rate (typically 6,000 rounds per minute). The M61 and its derivatives have been the principal cannon armament of United States military fixed-wing aircraft for fifty years. (Read more: en.wikipedia.org/wiki/M61_Vulcan)