Electric Driven Machinegun for Turret Applications
Following failure of the 7.62mm M73 tank machine guns, in around 1970, US Army decided to try some unorthodox solutions for a compact yet simple and reliable tank machine gun in the form of an externally powered weapon.
An additional benefit of an external power solution is that such weapon, if properly timed, will not leak powder gases back into the tank interior.
Initial work was commenced by the Hughes Tool Co, under contract to the US Army Weapons Command. The test weapon, unofficially known as EPAM (Externally Powered Armor Machine gun) used a 24VAC electric motor, which operated dual belt feeds and a rotating cylinder with cam slot that operated the reciprocating bolt.
The test weapon fired at about 550 round per minute, and had forward ejection through a long tube, so spent cases would fall outside the tank interior.
For various reasons, however, this system was abandoned in favor of the so called “Chain Gun” system, developed by the same Hughes Tool Co in around 1973.
The basic principle involved an externally driven endless chain that ran around the receiver and operated a more or less traditional rotating bolt and bolt carrier through a single abutment, fixed to the chain.
This principle was used to develop a wide array of weapons, including a 30mm helicopter gun for the AH64 Apache helicopter, several automatic cannon of the “Bushmaster” family, and one 7.62mm machine gun, the EX34.
Despite the fact that “Chain Gun” automatic cannon found wide acceptance in US Service and abroad, the “smaller brother” of the family found no luck in the US Armed forces; however, it was adopted as a vehicle gun in UK and Canada and is manufactured under license by Colt Canada (former DIEMACO) in Canada.
Also, in 2011 US-based ATK Corporation announced its newest addition to the “Bushmaster” family of externally operated weapons, the “Bushmaster 7,62mm” tank machine gun.
This weapon appears to be modified and slightly shortened and lightened version of the old “7,62mm Chain gun”.
This is an image showing the mechanism from an old report dated 1982 for the then called the Hughes Helicopter 7.62mm Chaingun.
Here is an image I've found from arcforums that shows a Hughes 7.62mm Chaingun on a AH-6E helicopter:
The British variant of the 7.62mm chaingun from the Challenger MBT is shown in the image below:
So this 'old' new gun is now offered again from ATK.
So what makes this gun so special:
- It's been designed from the ground for turret applications.
- It is electric powered and does not use propellant gases or recoil to drive the bolt
- This means you do not need fancy and complex electric chargers for your turret application. That eliminates one important problem.
- It has got a belt pull force in excess of the link strength; which means you can put a huge ammo box say 1.000 rounds in your turret and you dont need a powered forwarder to assist the gun. That eliminates another problem.
- The spent cases are ejected automatically to the outside from the frontal eject port. There goes another pain in the a** for the case collector or case eject chute.
- The gun is mounted using an easy to implement bayonet mount and does not need any recoil absorbers or soft mounts. So you dont need a fancy gun mount.
-You can change the barrel from inside the turret which is another nice feature
- There is much less fumes blown inside the turret compared with the gas operated guns.
- And this gun comes in a package that weighs only 15kg's.
It seems these advantages for turret applications was notified by Norwegians and Hagglunds of Sweden 'cause the new CV9030 for Norway comes with the 762mm Chaingun as seen below:
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