Modern Firearms - M73 and M219 tank machine guns
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M73 and M219 tank machine guns (USA)


M73 tank machine gun

 


M73C tank machine gun

 

 

Data for M73 machine gun

Caliber

7.62x51 NATO

Weight, kg

12.7

Overall length, mm

959

Barrel length, mm

559

Cyclic rate of fire, rounds per minute

500-625

Feed and capacity

Belt, rounds

 

 

 

Soon after WW2 the US Armed Forces requested development of a new, special-purpose tank machine gun, which was to be mounted coaxially on new tanks then in development. The very limited space available for the weapon dictated specific requirements for a short receiver and alternate left- or right-hand belt feed. Development was commenced in 1951 and continued, with certain delays and interruptions, until late 1958. Four designs were considered over that time, with designation codes from T197 to T200. The first design eventually became the favorite, and its improved T197E2 version was type-classified as M73 in early 1959. The T197 was developed by the government-owned Springfield Armory, and turned out to be a problematic son. The overly complicated design suffered from reliability problems, and further development at Springfield lead first to the M73E1 (1964) and then to the M219 (1972). Despite all efforts, even the M219 was still overly complicated and not reliable enough, and it was officially replaced in service in late 1970s and early 1980s by much more reliable M240 (license-built Belgian FN MAG) general purpose machine gun in ‘tank’ configuration .

 

The M73 is a short-recoil operated, air-cooled, belt-fed machine gun. It fires in automatic mode only, and from an open bolt. It is intended for vehicle use only.

To shorten the receiver as far as possible, the M73 has no conventional reciprocating bolt, which usually drives the feeding, locking and extracting functions in most automatic guns. Instead, each function (feeding, locking and extraction) is performed by a specific assembly or part. Locking is achieved by a laterally sliding breechblock, which is mounted within the barrel extension. When the trigger is depressed to fire the gun, the sear releases the barrel extension and it moves forward under pressure of a return spring. Upon this movement, a separate lever first operates the rammer which pushes the round out of the belt and forward into the chamber. Once the round is fully chambered, a special cam in the receiver moves breechblock laterally to close and lock the breech. Once the barrel is fully locked, the hammer is released to fire the cartridge. Upon recoil, the breechblock is slid open to the right via a cam in the receiver, then the cartridge is extracted and ejected using a special ejector unit of rather complicated design.

The barrel is easily removable, and its replacement procedure is somewhat similar to that of the German MG34 – the receiver is swung to the side around a pin which is parallel to the barrel, and then the barrel can be simply withdrawn to the rear from its jacket. The key difference is that the M73 has two axis pins at either side of the receiver, which work as pivot pins and locks alternatively, so the receiver can be turned to either side, depending on the installation.

The feed is of the one-stage type (push-through) from disintegrating steel belts with open links. The gun can be set to feed from either side, and spent cases are ejected downwards.

The gun is fitted with a manual trigger and charger, and can was usually fitted with an electric solenoid trigger.

There are no special mountings nor sights on the gun, as these are provided by the vehicle installation.

Modifications:

M73C: variant for external (roof-mounted) installations, with single spade grip, trigger and iron sights.

M73E1: the complicated gripping ejector is replaced by a much simplified fixed ejector to improve reliability and reduce jams

M219: an improved M73E1 with modified opening and closing cams in the receiver. Nevertheless, still a troublesome weapon