M197 electric cannon

M197 Gatling gun
Place of origin	United States
Service history
In service	1967–present
Used by	United States Marine Corps
Production history
Manufacturer	General Dynamics Armament Systems
Specifications
Cartridge	20 × 102 mm
Caliber	20 mm
Barrels	3-barrel (progressive RH parabolic twist, 9 grooves)
Rate of fire	Up to 1500rpm

The M197 electric cannon is a three-barreled electric Gatling-type rotary cannon used by the United States military.

Development

The M197 electric cannon' developed primarily for use by United States Army helicopter gunships. Development began in 1967 after experience in the Vietnam War revealed the inadequacy of the 7.62 mm 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 20 mm ammunition.

History

The M197 went into service on later marks of the AH-1 Cobra, using either the M97 or A/A49E-7 armament subsystems, and was also fitted in a ventral turret on the U.S. Marine Corps YOV-10D Bronco NOGS. It is also the basis of the GPU-2/A 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, with a total capacity including feeder system of 750 rounds. It has a cyclic rate of fire of 650 rounds per minute. Standard practice is to fire the cannon in 30 to 50-round bursts.

The M197 remains in use in the latest AH-1W Cobra and AH-1Z Viper gunships. Although the weapon's rotary drive is theoretically quite reliable, its ammunition feed has been anything but: Marine pilots initially reported an alarmingly high jam rate (sometimes greater than 30%). The USMC and the manufacturer are aware of the problem and in 2011 a link less feed system developed by Meggit Defense Systems was incorporated into the AH-1W and the Zulu's. The system is capable of holding 650 +/-3 rounds in the storage unit with approximately 40 rounds in the feed chute.

The M197 is also mounted as a chin turret in Italy's Agusta A129 Mangusta CBT helicopter, with a capacity of 500 rounds.

The XM301 was an improved M197 intended to be the gun on the later cancelled RAH-66 Comanche.

The weapon's current contractor is General Dynamics Armament Systems.

Ammunition

Designation	Type	Projectile Weight [g]	Bursting charge [g]	Muzzle Velocity [m/s]	Description
M53	API	?	4.2 g incendiary	1030	Penetration 6.3 mm RHA at 0-degree impact and 1000-m range.
M56A3/A4	HEI	102	9 g HE (RDX/wax/Al) and 1.5 g incendiary	1030	Nose fuzed round, no tracer. Effective radius to produce casualties to exposed personnel 2 meters, fragmentation hazard out to 20 meters. Penetration 12.5 mm RHA at 0 degree obliquity at 100m range
M242	HEI-T	?	?	?	Similar to M56 series of HEI rounds, but with a tracer element.
M246	HEI-T	102	8.0 g HE	?	Nose fuzed tracer round fired by M168 AA gun, self-destruct after 3 to 7 seconds of flight due to tracer burn-through.
M940	MPT-SD	105	9 g A-4/RDX/wax	1050	Multi-purpose fuzeless round, HE charge is initiated by the incendiary charge on the nose on impact. Self-destruct due to tracer burn-through. Penetration 12.5 mm RHA at 0 degree impact at 518 m range, or 6.3 mm at 60 degrees and 940 m.

See also

• M61 Vulcan
• XM301

References

Notes

Online

• GlobalSecurity.org M197
• US Army Helicopter Weapons Team
• The Aircraft Web Site
• General Dynamics Armament and Technical Products