There were a bunch of projects during the Cold War seeking to improve hit probability (as analysis had shown that most rounds fired don't actually hit) - generally, the idea was to fire several projectiles with each shot, to increase the statistical chance of at least one hitting.

The TKB-059 is probably the simplest and most basic attempt, by just literally tripling the gun and firing 3 bullets at once, but this obviously had the disadvantage of a lot of extra bulkiness, weight and recoil - it was just an experiment, more of a proof-of-concept (or attempt at one, anyway) that wasn't really expected to go very far. The West also attempted something simple, but from a different angle - the ammunition itself, with duplex & triplex rounds, where you'd have several bullets stacked in the cartridge itself, but those didn't work out due to accuracy issues caused by the several bullets interfering with one another.

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Most other attempts were based on firing several projectiles in very quick succession - for example, the Russian AN-94 (which is after the Cold War, but it's still building on this idea) had a special hyperburst mechanism that would fire at a rate of 1800 rounds-per-minute (while most regular rifles tend to be in the 600-800 RPM range)