M197 / GPU-2A
M197 Main components outlay
M197 as a door gun in an UH-1 Iroquois
Development of the M197 began in 1967 after experience in the Vietnam War revealed the inadequacy of the 7.62mm Minigun for gunship use. The M197 is essentially a lightened version of the General Electric M61 Vulcan cannon, with three barrels instead of six. Its maximum rate of fire is one quarter that of the Vulcan, largely to limit its recoil for light aircraft and helicopter use. It shares the Vulcan`s M50 and PGU series 20mm ammunition.
The M197 went into service on later marks of the AH-1 Cobra, and was also fitted in a ventral turret on the USMC OV-10D Bronco. It is also the basis of the GPU-2 gun pod, which incorporates the cannon, a battery and electric drive motor, and 300 rounds of linkless ammunition.
In the Cobra, the weapon is supplied with a magazine of 700 linked rounds. It has a cyclic rate of fire of 730 rounds per minute (▒ 50 rounds). Standard practice is to fire the cannon in 100-round bursts, allowing several minutes of cooling time between bursts.
The M197 remains in use in the latest AH-1W and AH-1Z Cobra gunships. Although the weapon's rotary drive is theoretically quite reliable, its ammunition feed has been anything but: Marine pilots report an alarmingly high jam rate (sometimes greater than 30%). The USMC and the manufacturer are aware of the problem, but no specific fix has been incorporated on the AH-1Z. In the meantime, crews have been trained in techniques intended to minimize the risk of jamming.
The weapon`s current contractor is General Dynamics Armament Systems.
three-barrel rotary cannon
hydraulically operated, electrically fired
20 mm (0.79 in)
(complete): 60 kg (132 lb)
2.11 m (83.2 in)
Rate of fire:
300 - 1500 RPM
1,036 m/s (3,400 ft/s)