M230 chain gun

M230 Chain Gun
An M230 Chain Gun mounted on an AH-64 Apache in Logar Province, Afghanistan, in March 2009.
Type	Automatic cannon
Place of origin	United States
Service history
In service	1986–present
Used by	United States, and other countries
Wars	Persian Gulf War – present
Production history
Designed	1975
Produced	1975–present
Specifications
Weight	55.9 kg (120 lb)
Length	1,638 mm (64.5 in)
Width	254 mm (10.0 in)
Height	300 mm (11.8 in)
Cartridge	M788 Target Practice (TP) M789 High Explosive Dual Purpose (HEDP) M799 High Explosive Incendiary (HEI)
Caliber	30 x 113 mm
Action	Chain gun
Rate of fire	625 +/- 25 rpm
Muzzle velocity	805 m/s (2,641 ft/s)
Effective firing range	400–500 m (437–547 yd)
Maximum firing range	15,600 m (17,100 yd)

The Hughes M230 Chain Gun is a 30 mm, single-barrel automatic cannon developed by Hughes and now manufactured by Alliant Techsystems. It is an electrically operated chain gun, a weapon that uses external electrical power (as opposed to recoil or expanding gas generated by the firing cartridge) to cycle the weapon between shots.

In 1972 Hughes Helicopters began a company-funded research effort to design a single machine gun to fire the U.S. Army's M50 20 mm round. By April 1973, the program had fired test rounds in more powerful 30 mm WECOM linked ammunition, from a prototype (A model). In January 1975 a model "C" was added, a linkless version for the proposed Advanced Attack Helicopter YAH-64; the helicopter was eventually adopted as the AH-64 Apache, with the model C as standard armament. The linked ammunition version was intended for the AH-1S Cobra, but was later dropped.

The M230 Chain Gun is the Area Weapon System on the AH-64 Apache attack helicopter and is also used on the MH-60L Direct Action Penetrator (DAP). The M230 is mounted on the chin turret. It uses a 2 hp electric motor to fire 30 mm linkless ammunition at a rate of 625 (±25) rounds per minute. The practical rate of fire is about 300 rounds per minute with a 10-minute cooling period as the gun is air cooled. The gun has a positive cook-off safety for open bolt clearing, and double ram prevention. Spent casings are ejected overboard through the bottom of the gun.

The mount on the AH-64 uses secondary hydraulics to move the gun. Elevation is provided via a single hydraulic actuator located on the gun's centerline just forward of the pivot point. The gun is spring-loaded to return to its centerline stowed position with the barrel angled up about eleven degrees in the event of a loss of hydraulic power. This allows the gun, which is mounted below the copilot station, to collapse cleanly into its designed space between the pilot stations in the event of a hard landing. This prevents the gun from entering the pilots stations and becoming a hazard.