Tuesday, May 8, 2018

M73 Machine Gun - A Forgotten Weapon (Video)

m73 barrel extension ebay
$45 - Grab it!
I saw this weird thing on eBay - It's a locking frame of an M73A1 Coaxial Machinegun, also known as the M219 tank gun.  These shortlived weapons were used in the 1960's for mounting onto tanks and were quickly replaced by the M60 due to these not being very reliable guns.  The design is interesting - the barrel extension housed all major components - barrel, bolt, feed mechanism - so the design is simple and has a small profile.  It's said to be the most compact action of any belt-fed .308 machinegun (at the time, maybe even today).


Preventive Maintenance Monthly M73
The Preventive Maintnance Monthly article on the M73
Things I learned about this gun:
  • Fired from an open bolt/fixed firing pin
  • Recoil operated
  • Used some kind of rotating arm/rammer to send rounds into battery
  • The rammer rotated on the barrel extension assembly
  • Feeds from left or right, using disintegrating links
  • Quick-change barrel simply drops into extension
  • No bolt - uses a wierdo breech block - like a falling block action, I guess.
Information is hard to find on this.  I think a few people on the 1919a4 forums have complete kits of this.  No known semi-automatic versions of this exist, and as far as I can tell, no Class 3 MG owner has a complete one.  Seems like an interesting project, but also complex.


Still trying to wrap my head around how exactly that bolt face engages the cartridge.  It's hard to find a good diagram of this and the various drawings of this have the breech mechanism oriented in weird angles.  The jist of it is that breech block contains the firing pin and sidles in somehow to lock the barrel to the extension and fire the cartridge at the same time.
Preventive Maintnance Monthly M73 breech block
M73 breech blocks - how do they work?
Parts are available through GunPartsCorp and Sarco, though I'm mostly sure that top cover components and other stuff are missing and not available.

For $45 with a presumably complete arm assembly, that barrel extension might be a good deal considering Sarco and GPC are selling them for $200.

Related Reading
M73 Article on Wikipedia
Small Arms Review - The M73/M219 Machine Gun: Mama's Ugly Baby
Tank and AFV News - "The sad story of the M73 coax machine gun"
GunPartsCorp - M219 parts
Sarco - M73 parts