M197 electric cannon
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The M197 electric cannon is a 20 mm three-barreled electric Gatling-type rotary cannon used by the United States military. Wikipedia
Manufacturer: General Dynamics Armament Systems
Barrels: 3-barrel (progressive RH parabolic twist, 9 grooves)
Caliber: 20 mm
In service: 1967–present
Length: 1,828 millimetres (72.0 in)
Muzzle velocity: 1,030 m/s (3,300 ft/s)
Rate of fire: 750-1500 rpm