Riverine etc. ...

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I think it was a multi-use hull. After the end of the USSR a lot of vessels were repurposed but I can't be sure. I don't speak Russian

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57mm ZIF-71 Single Mount

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57mm ZIF-31 Twin Mount

Mount/Turret Data
Designation
    • Russia / USSR Open Twin
        ◦ Submarine AA Mount: SM-24-ZIF, SM-24-ZIF1
        ◦ AA Mount: ZIF-31, ZIF-31B, ZIF-31BS, ZIF-31S
Weight
SM-24-ZIF: 16,094 lbs. (7,300 kg)
ZIF-31B: 23,810 lbs. (10,800 kg)
Elevation
SM-24-ZIF: -6 / +85 degrees
SM-24-ZIF1: -0 / +85 degrees
ZIF-31: -10 / +85 degrees for all versions
Elevation Rate
SM-24-ZIF: 20 degrees per second
ZIF-31, -31B: 25 degrees per second
ZIF-31BS, -31S: 22 degrees per second
Train
SM-24-ZIF: -147 / +147 degrees for (Pr.611 subs)
SM-24-ZIF: -140 / +140 degrees for (Pr.613 subs)
ZIF-31: -200 / +200 degrees for all versions
Train Rate
SM-24-ZIF: 25 to 30 degrees per second
ZIF-31, -31B: 30 degrees per second
ZIF-31BS, -31S: 27.5 degrees per second
Gun recoil
9.35 -12.52 in (23.5 -31.8 cm)

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57mm ZIF-75 Quad Mount