Gun maker Windsor Arms Co. of Windsor, Vermont, brought their suppressed Argentinian FMK-3 submachine gun to the Green Mountain Boys machine gun shoot in Eden, Vermont in July 2018.
The FMK-3 is a select fire, blowback operated submachine gun of Argentine origin. It was designed by Fabricaciones Militares in 1974. Approximately 30,000 were produced for the Argentine military, and is still currently in use.
It was based on the U.S. M3 A1 submachine gun, more commonly referred to as the ‘Grease Gun’. But instead of the firing the .45 ACP round like the M3A1, the FMK-3 fires the 9×19mm cartridge at a rate of 650 rounds per minute.
Despite having a good design, Windsor Arms made a few improvements when they built their kit. They added a 3-lug adaptor to the barrel to facilitate quick adding and removing of a suppressor. They also swapped out the factory sights, which they thought were cheap, and added HK-style adjustable sights, such as those found on HK MP5s. Other than that, the gun is stock.
It’s an incredibly smooth shooting and reliable submachine gun. It’s very easy to control, and according to LaMarche, if you were to hold a tin can beside the gun as it fired, you could easily catch all of the ejected brass. It’s got a very consistent ejection pattern of spent shells.