Well, guess what--Salyut 3 had a machine gun. The station had a 23 mm rapid-fire cannon mounted on the outside, along the long axis of the station "for defence against US space-based inspectors/interceptors". Combat engagements would have been leisurely by Star Wars or fighter jet standards, since the only way to aim the cannon was to point the entire station at the target, using its attitude gyros.
The survival kit in the Soyuz spacecraft which ferries cosmonauts to and from the Mir space station is said to contain, among other things, a pistol and ammunition. This is not so much to put down the occasional space mutiny, but as a precaution in case of an off-course landing in a region with dangerous wildlife. In March 1965, due to failure of the prime retro-rocket system, the crew of Voskhod 2 landed in a remote region in the Ural Mountains and rescue crews could not reach them until the next day. They were forced to retreat to their re-entry capsule to escape wolves in the forest where they landed.
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