The sad story of the M73 coax machine gun

sad storyOne of the more surprising stories of cold war US tank development is the M73/M219 machine gun.  Developed for use in US armored vehicles, the M73 served most prominently as the coax machine gun in the M48/M60 “Patton” series of tanks and the M551 Sheridan light tank.  During its time of service, the M73 distinguished itself as one of the worst machine guns ever adopted by the US military, suffering from numerous malfunctions which lead to frequent jamming.  This was particularly frustrating for US tankers who were accustomed to the reliability of the .30 and .50 cal machine guns designed by John Browning which equipped US tanks during WW2 and the early cold war period.

A nice overview of the sad history of the M73/M219 is provided by an article over at the small arms review. The article sums up the M73/M219 saying:

In retrospect, the design of the M73/M219 was an accumulation of novel concepts that should have been thoroughly tested in the application before finalizing the design. The off and on development program challenged the ever-changing design teams with a new learning curve every time the project was restarted. It was a costly program in time, assets, money and loss of face. She was an ugly little baby and somebody should have told her Mama so.

For those interested in primary documents, here is a link to a government report from 1975 detailing tests to find a suitable replacement for the M73/M219.  Interestingly, the guns tested include not just US designs, but also the Canadian C1, the German MG3, the MAG58 from Belguim, the British L8A1, the French AAT52 and even the Soviet PKM.

Attribute Analysis of the Armor Machine Gun Candidates (PDF)

Here is a video showing the operation of the M73.


And finally, here are a couple PS Magazine articles on The M73.  These are part of the “Be Your Own Inspector” series aimed at helping train soldiers properly maintain their equipment.

Issue 130 (1963)

Issue 200 (1969)


  1. I’ve never heard of the C1 machine gun – I’ve always thought the M1919 in Canadian service was designated the C5. Either way, an ironic gun to be evaluating as an M73 replacement.


    • The C1 was the early basic version of the C5A1. The C1 had numerous problems that were addressed in the product improved C5A1. The primary difference between this version of the M1919A4 and other versions converted to 7.62mm NATO is the C1/C5A1 used the M13 links. Other 7.62mm NATO versions of the M1919A4 used a modified M2 link. In the Vietnam War, the US Navy modified several thousand .30 caliber M1919A4s to the MK21 Mod O Browning which used the 7.62mm NATO with M13 links. The primary difference is the 7.62mm NATO belts were fed into the guns with the top of the links down. These guns were left in Vietnam when the swift boats were turned over to the South Vietnamese Navy. Only one or two of the guns still exist.


  2. In the Army photograph comparing receiver lengths between the M37 and M73, the aft rather than the front of the feedway was selected as the forward most measurement. This is presumably because the two machine guns fire rounds that are different lengths so using the aft of the feedway in this case might be better for this comparison.


  3. Nearoffutt says:

    The poor thing, even Connie in PM couldn’t make the thing work. I was in the loader’s slot in the M48A5. When the TC ordered COAX, my job was to abandon the M60D on top and drop down to feed ammo to the M219 or it would malfunction. We kept the poor thing installed at an angle to try and help it fire. The10K rounds would last the entire of WWIII as it rarely fired more than three rounds in a row.


  4. As an M-48A5C, M-60 and M-60A1 loader and gunner in the early ’70’s I remember the ’73/219 well. Not good memories though. We tried every trick in the book to make them fire properly. Cleaning, parts swapping (which probably made things worse) – although tilting them slightly sometimes helped. Loader used to always have the charging chain in one hand and heel of other hand on the firing solenoid during coax engagements and be ready for the gunner to announce “Misfire”. Jerk the chain, “Up”. “Misfire – jerk-up-misfire. Repeat repeatedly. Jerk it fast and keep punching the solenoid enough you get get a pretty high rate of fire in a comical single shot process. Between the ‘219 and the M-85 .50cal, another PIA, only the main gun could really be relied upon, thankfully for that at least. At the time we did not know the Army was looking to replace the COAX. When the got the ‘240 later on in the Brads and Abrams it was like a miracle. A coax that actually worked!! And the M-2 .50 on the Abrams was an improvement also because the M-85 used

    As an aside, it wasn’t all bad, as placing a grease soaked toilet paper roll on top of a 105mm TPT round made pretty pictures in the sky!

    Liked by 1 person

  5. Panzer Jeff says:

    As a M 551 crewman and tank commander in Vietnam in 1969-1970, I can state unequivocally that the M 73 coaxial machinegun was the biggest piece of crap ever fielded as a machinegun by an American army. Through almost a year of combat the most I ever got out of the piece of shit was two-and-a-half bursts before jamming. It damn near cost me and my crew our lives one fine day in May of 1970, near a lovely piece of local scenery called The Rockpile. Upon reflection, however, it’s exactly what one should have expected from the multi-cursed Sheridan concept.


  6. The M73/M219 was the probably the worst modern machinegun used by the US military. The Chauchaut can only be worse. The worst part of it is Rock Island Arsenal was developing a 7.62mm NATO version of the highly reliable M37 Tank Gun (Browning) and it was dropped in favor the M73. The M37 Browning was considered the Cadillac of the .30 caliber Browning and was well liked. THE M85 .50 caliber was just as bad as the M73 and it was quickly replaced by the M2 Browning which was used on early US armored vehicles. When the US supplied M60 tanks to the Israelis they quickly removed the M85s out of their M60s.


  7. The M73 was a coax mounted weapon in the cupola of the T.C. Position on a APC 113 flamethrower track during Vietnam. I was a TC on such a track from Sept 1968 until March 1970. It was mounted at a strange angle inside the cupola due to a periscope for the TC’s use when the hatch was buttoned up. In this configuration believe it or not the thing performed flawlessly. I also had a .50 cal mounted on top of the cupola for use during firefights when the flamethrower was not utilized. I used the M73 when inside the cupola after firing the flamethrower. After the napalm was exhausted I would remain standing inside the hatch with my head outside and fire the M73 traversing the cupola all the while. The thing never malfunctioned, and it had a high rate of fire. The only problem I had was keeping the port clear of links and spent brass which would fill up and cause a jam. It had to be cleared occasionally when firing a lot of ammo. It was simple to clear when reloading anyway. I really liked the thing. It could really put down some suppressive fire. When inside firing like that I really liked to put down good rate of fire to keep from getting hit with an R.P.G. while inside that thing which I was always afraid of. Maybe I was just lucky to have good functioning M73’s or perhaps it was the way it was mounted inside the cupola, but either way they gave me great service while with the 1st Bn 5th Mech Inf of the 25th Inf Div. Maybe the mounts were a design flaw in tanks.


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