Hughes EX34 Chain Gun: One of the most significant developments in small arms technology

Eric Sof

Hughes EX34 Chain Gun in 7.62mm NATO caliber

Hughes Helicopters manufactured the EX34 Chain Gun, which made a change and announced a new era of chain weapons. It was a significant change in manufacturing this type of machine gun in the last fifty years.

Mechanical machine guns are as old as the industry, names like Gatling, Gardner, and Nordenfelt having been prominent in this field in the 1870s, but with the development of the self-powered Maxim, they were rendered obsolescent. They reappeared when it became apparent that only mechanical solutions could provide the high rate of fire demanded by modern aerial combat, and the Gatling was revived as the electrically-driven Vulcan aircraft cannon.


But they seemed to be out of the question for land force use until Hughes perfected this design, one of the most significant developments in small arms technology in the last fifty years. It has been adopted in 7.62mm caliber as a tank and armored vehicle gun by the United States and British armies and is likely to be taken into use by several others in the future. In 25mm and 30mm caliber, it is used by the United States forces as a helicopter weapon and has also been evaluated by the British Army as armament for their Fox armored car.


The heart of the EX34 Chain gun is a loop of commercial roller chain which lies on the bottom of the receiver and is driver round by a gear, driven by an electric motor. Attached to this chain is a lug that engages in the bolt carrier so that as the chain moves forward, a cartridge is fed into the breech, and the bolt is rotated and locked. As the chain lug moves, following the loop path, across the receiver’s front, there is no motion of the bolt carrier; the breech stays locked, and the cartridge is fired.

Diagram of chain driven EX34 chain gun
Diagram of chain-driven EX34 chain gun (Photo: Hughes)

Then as the chain lug turns the corner and begins to run back down the other side of the receiver, the bolt is unlocked and opened, the carrier pulled back, the case ejected. As the chain lug makes its fourth side of the receiver, there is no motion on the carrier, and there is a brief pause that permits the cooling of the open barrel.

The delay, or ‘dwell,’ with the closed bolt acts as a safety in case of a hangfire (delayed ignition of the cartridge). If the cartridge has not fired by the time the lug has made its crossing, the gun stops and the operator has to restart it, thus giving ample time for the most prolonged hand fire to discharge itself safely. If the round is a misfire, once the gun is restarted, the dud round is extracted and ejected safely.

Ejection is done down a forward-facing tube since this gun is designed for use in armored vehicles, and the empties (and any unfired rounds) are thrown clear of the turret. Since the weapon is sealed, fumes cannot escape into the vehicle but are ejected either through a jacket sleeve around the barrel or through the ejector tube, keeping the air in the tank relatively clean.

M230 Chain Gun mounted on AH-64 apache
An M230 Chain Gun mounted on a US Army AH-64 Apache at the Berlin Air Show 2018 (Photo: USAF)

It will be apparent that the rate of fire is infinitely variable by simply controlling the speed of the drive motor, though, in practice, the controls are such that either single shots or 600 rpm are available. The EX34 Chain Gun also has the advantage of providing a positive mechanical lift for the ammunition belt instead of relying upon the recoil of the gun’s moving parts to actuate the feed. This, together with the precise control and inter-operation of the entire operating cycle, makes the EX34 Chain Gun one of the most reliable and smoothly operating machine guns in existence.

Technical specifications

Manufacturer: Hughes Helicopters (now part of Northrop Grumman), Culver City, CA90230, United States
Designed: 1973
Service: 1983-present
Type: mechanical, belt-fed, machine gun
Caliber:  7.62mm NATO
Barrel: 22 in (558 mm)
Weight (empty): 29.1 lbs (13.2 kg)
Effective firing range: 1500 m (1640 yd)
Rate of fire: 625±25 rounds per minute
Magazine capacity: belt feed

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