Russia / USSR
57 mm/78.7 (2.24") SM-24-ZIF
57 mm/78.7 (2.24") ZIF-31
Updated 19 November 2008
Development started on this weapon in 1947 as a submarine AA weapon.  A prototype of the SM-24 twin mount was built in 1948-1950.  During testing on the prototype several defects were discovered and the mounting was sent back for rework.  Following a redesign to correct the faults an improved version was tested from 1951-1953.  This version was accepted into service in 1955 and by 1991 there were 70 mounts in the Soviet Navy.

ZIF-31 was a surface-ship version of the SM-24 mount which was designed in 1954 and accepted into service in 1955.  By 1981 there were 265 ZIF-31 mounts in the Soviet Navy.  There were four different versions of the mount, the main difference being that ZIF-31 and ZIF-31S had a central fire control system while the ZIF-31B and ZIF-31BS had only local control.

These weapons had significant operational problems, most of them connected to the fact that they were in open mounts, which caused problems for ships operating in the Arctic Ocean and meant that they lacked NBC protection.  The guns themselves were clip fed, which lowered down their practical rate of fire.  They could only be fired for 50 rounds at a time before they had to be cooled by running sea water through the barrel for 1-1.5 minutes using a special nozzle.

The barrel was of monobloc construction.  The automatic mechanisms operated via the recoil forces.  Both barrels were mounted on a common cradle.  Ammunition was supplied in clips with each clip holding 3 rounds.
WNRussian_57mm-78_zif-31_pic.jpg

ZIF-31 twin mounting
WNRussian_57mm-78_zif-31_SM24_pic.jpg

SM-24 submarine mount
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Gun Characteristics
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Designation 57 mm/78.7 (2.24") SM-24-ZIF
57 mm/78.7 (2.24") ZIF-31
Ship Class Used On SM-24-ZIF:  Zulu (Pr. 611), Whiskey (Pr. 613) class submarines

ZIF-31:  Surface ships
Date Of Design SM-24-ZIF:  1951
ZIF-31:  1954
Date In Service SM-24-ZIF:  1951
ZIF-31:  1954
Gun Weight 1,366.6 lbs. (619.9 kg)
Gun Length oa 176.6 in (4.486 m)
Bore Length 168.31 in (4.275 m)
Rifling Length 153.47 in (3.898 m)
Grooves SM-24-ZIF:  24
ZIF-31:  15
Lands N/A
Twist N/A
Chamber Volume 92.15 in3 (1,510 cm3)
Rate Of Fire SM-24-ZIF:  100-150 rounds per minute
ZIF-31:  50 rounds per minute before barrel had to cooled
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Ammunition
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Type Fixed
Weight of Complete Round Russia / USSR
   Tracer-FRAG (UOP-281) - 14.0 lbs. (6.36 kg)
   Tracer-FRAG (UOP-281U) - 14.1 lbs. (6.40 kg)
   HE (UFB-71) - 14 lbs. (6.35 kg)
Projectile Types and Weights Russia / USSR
   Tracer-FRAG (UOP-281) - 6.17 lbs. (2.8 kg)
   Tracer-FRAG (UOP-281U) - 6.17 lbs. (2.8 kg)
   HE (UFB-71) - 6.17 lbs. (2.8 kg)
Bursting Charge Tracer-FRAG (UOP-281) - 0.37 lbs. (0.168 kg)
Tracer-FRAG (UOP-281U) - 0.34 lbs. (0.154 kg)
Projectile Length Tracer-FRAG (UOP-281U) - 3.9 calibers without the tracer
Complete Round Length Tracer FRAG (UOP-281) - (53.6 cm)
Tracer FRAG (UOP-281U) - (53.6 cm)
Cartridge Case Type, Size and Empty Weight Lacquered steel or drawn 70:30 brass, 57 x 348 mm SR, N/A
Propellant Charge 2.65 lbs. (1.2 kg)
Cartridge - 4.92 lbs. (2.32 kg)
Muzzle Velocity Russia / USSR:  3,346 fps (1,020 mps)
Working Pressure 44,090 psi (3,100 kg/cm2)
Approximate Barrel Life N/A
Ammunition stowage per gun N/A
Notes:

1) The Army S-60 fires the same ammunition.

2) Army guns are also supplied with APC rounds (BR-281 and BR-281U).  Both of these use a ballistic cap and can pierce roughly 9.6 cm of armor at 0 degrees obliquity at 1,000 meters.
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Range
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Elevation With 6.17 lbs. (2.8 kg) Tracer-FRAG Shell
Max Ballistic Range 9,210 yards (8,420 m)
Self-destruct Range 7,600 yards (6,950 m)
Notes:

1) The SM-24 was controlled by a MZP-57-2A-1 optical gun sight which could engage aircraft out to a maximum range of 5,580 yards (5,100 m) flying at speeds of up to 600 knots (1,080 kph).  It could also be used against surface targets within 8,000 yards (7,320 m).

2) The ZIF-31 used the Fut-B control system which could could be used against aircraft targets at ranges of up to 6,010 yards (5,500 m) flying at speeds of up to 600 knots (1,080 kph).  It could also be used against surface targets within 12,000 yards (10,980 m).

3) The ZIF-31B and ZIF-31BS used the AMZ-57-2 optical gun sight which had a maximum range against aircraft of 5,470 yards (5,000 m) flying at speeds of up to 600 knots (1,080 kph).  However, as these weapons were local control only, these numbers may be optimistic.  It could also be used against surface targets within 8,000 yards (7,320 m).
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Mount / Turret Data
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Designation Russia / USSR Open Twin
   Submarine AA Mount SM-24-ZIF
   Submarine AA Mount SM-24-ZIF1
   AA Mount ZIF-31
   AA Mount ZIF-31B
   AA Mount ZIF-31BS
   AA Mount 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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Data from
"The Naval Institute Guide to World Naval Weapon Systems 1991/92" by Norman Friedman
"Jane's Ammunition Handbook:  Ninth Edition 2000-2001" edited by Terry J. Gander and Charles Q. Cutshaw
"Entsiklopedia Otechestvennoi Artillerii" (Encyclopedia of Fatherland [Russian] Artillery) by A.V. Shirokorad
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Special help by Vladimir Yakubov