Russia / USSR 57 mm/78.7 (2.24") SM-24-ZIF and ZIF-31

Russia / USSR
57 mm/78.7 (2.24") SM-24-ZIF
57 mm/78.7 (2.24") ZIF-31
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People's Republic of China
57 mm/70 (2.24") Type 59
57 mm/70 (2.24") Type 76
Updated 21 November 2007

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.

In addition to the standard air-cooled version, the People's Republic of China has developed a water-cooled version of this gun known as the Type 76 which uses more powerful ammunition.

ZIF-31 twin mounting

SM-24 submarine mount

Gun Characteristics .

Designation	Russia / USSR 57 mm/78.7 (2.24") SM-24-ZIF 57 mm/78.7 (2.24") ZIF-31 PRC 57 mm/70 (2.24") Type 59 57 mm/70 (2.24") Type 76
Ship Class Used On	SM-24-ZIF: Zulu (Pr. 611), Whiskey (Pr. 613) class submarines ZIF-31: Surface ships Type 59: Surface Ships Type 76: Surface Ships
Date Of Design	SM-24-ZIF: 1951 ZIF-31: 1954 Type 59: 1966 Type 76: 1976
Date In Service	SM-24-ZIF: 1951 ZIF-31: 1954 Type 59: 1966 Type 76: 1976
Gun Weight	1366.6 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 Others: N/A
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 Others: N/A

Ammunition .

Type	Fixed
Weight of Complete Round	Russia / USSR Tracer-FRAG (UOP-281): 14 lbs. (6.35 kg) Tracer-FRAG (UOP-281U): 14 lbs. (6.35 kg) HE (UFB-71: 14 lbs. (6.35 kg) PRC Type 59 - HE-T: 16.3 lbs. (7.4 kg) Type 76 - HE-T: 16.8 lbs. (7.6 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) PRC Type 59 - HE-T: N/A - probably about 6.17 lbs. (2.8 kg) Type 59 - AP-T: N/A Type 76 - HE-T: N/A
Bursting Charge	Tracer-FRAG - 0.34 lbs. (0.153 kg)
Projectile Length	Tracer-FRAG (UOP-281U) - 3.9 calibers without the tracer PRC: N/A
Complete Round Length	Tracer-FRAG (UOP-281U): 21.1 in (53.5 cm) Type 59 - HE-T: 21.1 in (53.5 cm) Type 59 - AP-T: 21.1 in (53.7 cm) Type 76 - HE-T: 23.3 in (59.1 cm)
Cartridge Case Type, Size and Empty Weight	Brass or Steel, 57 x 348 mm, 2.47 lbs. (1.12 kg)
Propellant Charge	2.65 lbs. (1.2 kg)
Muzzle Velocity	Russia / USSR: 3,346 fps (1,020 mps) PRC Type 59 3,346 fps (1,020 mps) PRC Type 76: 3,280 fps (1,000 mps)
Working Pressure	44,090 psi (3,100 kg/cm²)
Approximate Barrel Life	over 1,500 rounds
Ammunition stowage per gun	N/A

Range - Russia / USSR and People's Republic of China Type 59 .

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).

Range - People's Republic of China Type 76 .

Elevation	With HE-T
Maximum Range	16,400 (15,000 m)
AA Ceiling	32,800 feet (10,000 m)

Mount / Turret Data .

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 PRC Open Twin Type 59 (air cooled guns) Type 66 (air cooled guns) Type 76 (water cooled guns)
Weight	SM-24-ZIF: 16,094 lbs. (7,300 kg) ZIF-31B: 23,810 lbs. (10,800 kg) Type 66: 23,140 lbs. (10,500 kg) Others: N/A
Elevation	SM-24-ZIF: -6 / +85 degrees SM-24-ZIF1: -0 / +85 degrees ZIF-31: -10 / +85 degrees for all versions Type 66: -5 / +85 degrees
Elevation Rate	SM-24-ZIF: 20 degrees per second ZIF-31, -31B: 25 degrees per second ZIF-31BS, -31S: 22 degrees per second Type 66: 25 degrees per second (can move imprecisely at 40 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 Type 66: N/A
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 Type 66: 25 degrees per second (can move imprecisely at 40 degrees per second)
Gun recoil	9.35 -12.52 in (23.5 -31.8 cm)

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
Special help by Vladimir Yakubov