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.
| 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 |
| Type | Fixed |
|---|---|
| Weight of Complete Round |
|
| Projectile Types and Weights | |
| 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 |
| Elevation | Distance |
|---|---|
| Max Ballistic Range | 9,210 yards (8,420 m) |
| Self-destruct Range | 7,600 yards (6,950 m) |
| Type | Control | Target | |
|---|---|---|---|
| Aircraft (up to 600 knots (1,080 kph)) |
Surface | ||
| SM-24 | MZP-57-2A-1 optical gun sight | 5,580 yards (5,100 m) | 8,000 yards (7,320 m) |
| ZIF-31 | Fut-B control system | 6,010 yards (5,500 m) | 12,000 yards (10,980 m) |
| ZIF-31B and ZIF-31BS | AMZ-57-2 optical gun sight | 5,470 yards (5,000 m)1a | 8,000 yards (7,320 m) |
- ^As these weapons were local control only, the range and target speed may be optimistic.
| Designation |
|
|---|---|
| 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) |
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 from Vladimir Yakubov