In 1975, the Soviet Union did something that had never been done in space before. They fired a gun from a space station, the one and only time such a thing has happened. It was an event that was only uncovered after the fall of the USSR in the early 1990s.
The gun the Soviets fired in space wasn’t a handgun, but was, in fact, a cannon that was based on the design for a cannon that had been used in a Soviet bomber. The R–23M Kartech cannon was developed in the mid-1960s and was to be used for a secret Soviet project called Almaz. The intention of the Almaz project was to put space stations into orbit that would be used only for military purposes with the cannon being used as a countermeasure to any American threat in space.
The secretive space stations, and their existence, were masked under the name of the Soviets other, publicly known, space station program called Salyut. Out of seven Salyut space stations that were launched from 1971 to 1982, three of those stations were under the Almaz project. The actual existence of the Almaz project wasn’t known until after the Cold War was over.
The USSR installed the R-23M cannon on Salyut-3 (the depiction is above) which was launched on June 25, 1974. The crew departed Salyut-3 almost a month later, and the Soviets planned a test firing of the cannon on January 24, 1975, just a few hours before the station was to be deorbited and destroyed during reentry. Russian officials picked this time because they weren’t sure what the effect of the firing would have on the space station.
But firing the cannon wasn’t that easy. To aim the cannon, the 20-ton space station had to be turned to face the intended target, which was no easy task, and an onboard optical site would have allowed a cosmonaut to fire the weapon, if they had been present. The Soviets fired around three bursts from the cannon for a total of about 20 rounds, and the thrusters on the station were lit to counteract the recoil of the cannon after it had fired.
The test results from the firing of the cannon still remain classified to this day. What the cannon looked like had also been a mystery until 2015 when a Russian television show called Voennaya Priemka showed the cannon as it was displayed in the museum of the bureau where it had been designed.