Operating Systems

Chain

The Hughes Chain Gun is often misconceived to operate on the Gatling principle but is in fact an entirely different and novel system. Like the Gatling gun, the Chain gun cycles using external energy from a motor, but in this fixed, single-barrel design the motor drives a roller chain that moves the bolt forward and backward. Ian Hogg describes a 7.62mm version in Military Small Arms of the 20th Century:

The chain is driven by an electric motor, and a shoe on the chain engages in the bolt, carries it forward to chamber a round, holds it closed, then retracts it to extract the spent case. Cams rotate the bolt head to lock into the barrel and also actuate the firing pin as the bolt locks. A dynamic brake on the motor ensures that when the trigger is released the bolt stops in the open position, so that there is no danger of cook-off. The belt feed is also driven by the motor, independently of the bolt mechanism, so that there is ample power to handle long belts, particularly in a vehicle bounding over rough country. The Chain Gun is particularly well suited to tank installation since case ejection is forward, under control, and the relatively long bolt closure dwell time reduces the amount of fumes released into the vehicle. The Hughes Chain gun is one of the few new operating principles which have appeared in recent years[.]

The Chain Gun is developed in calibers ranging from 7.62 NATO through 30mm, and it is found for example aboard the US Army Apache Helicopter and in the Bradley Infantry Fighting Vehicle. This simple and direct system has several advantages in low-cyclic-rate, vehicle-mounted applications.

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