This weapon was first designed in 1946 and was used in a number of experimental mountings made during 1946-50. The first was the SM-21 single gun mount made in 1947-48 and tested in 1949. This was found to be deficient in many areas and was cancelled. The requirements were then rewritten and a new design was produced accordingly. A prototype was completed by the end of 1950 and tested in 1951. This proved more successful and the mount was accepted into service in 1954. Additional designs for the SM-16 stabilized twin mount, the SM-17 unstablized twin mount plus others using this gun did not go into production.
In 1946 the design of the SM-20 quad mount was started with a different gun barrel, but after the SM-7 gun proved successful the design was reworked to use this weapon and the mount was accepted into service in 1957 with 121 being built that year. This mounting was unsyncronized which meant that while the top barrels were recoiling the bottom barrels were firing. This caused significant dispersion, but that was considered desirable for an AA weapon. The barrels were in a single cradle. The guns were cooled between firings by running sea water through the barrels from a fire hose with a special nozzle. The mounts could be fired by a central control system or from a local control.
In 1952 a ZIF-68 quad mount was started to replace the B-11 mounts on the Pr. 68 light cruisers. In 1954 the mount was tested and by 1955 thirty mounts were built. Seven cruisers were supposed to receive the ZIF-69 mount, but in 1959 they were all cancelled and the mounts were placed in storage as they were too big to install in destroyers or similar warships. These remained in storage until at least 1991. The mount was nearly identical to the SM-20 gun mount, the main difference being the electrical systems.
The barrel was of monobloc construction and the gun was a recoil-operated automatic. The breech was piston type. The guns can be either belt or clip fed.
| Designation | 45 mm/78 SM-7 |
|---|---|
| Ship Class Used On |
|
| Date Of Design | SM-7 barrel: 1946 SM-21: 1952 SM-20: 1952 ZIF-68: 1954 |
| Date In Service | SM-21: 1954 SM-20: 1957 ZIF-68: Not in Service |
| Gun Weight | 888 lbs. (402.8 kg) |
| Gun Length oa | 157.87 in (4.020 m) with breech and flash reducer |
| Bore Length | 137.8 in (3.5 m) |
| Rifling Length | 121.38 in (3.083 m) |
| Grooves | 12 |
| Lands | N/A |
| Twist | N/A |
| Chamber Volume | N/A |
| Rate Of Fire | SM-21: 135 - 160 rounds per minute cyclic SM-20 and ZIF-68: 540 - 640 rounds per minute cyclic for all 4 barrels Length of burst until cooling required: 50 rounds |
| Type | Fixed |
|---|---|
| Weight of Complete Round | All: 9.97 lbs. (4.52 kg) |
| Projectile Types and Weights | HE (F-75): 3.11 lbs. (1.41 kg) FRAG (OR-75): 3.11 lbs. (1.41 kg) |
| Bursting Charge | HE (F-75): 0.11 lbs. (0.05 kg) FRAG (OR-75): 0.13 lbs. (0.06 kg) |
| Projectile Length | HE (F-75): 5.3 calibers FRAG (OR-75): 4.9 calibers |
| Propellant Charge | N/A Cartridge weighs 4.41 lbs. (2 kg) filled |
| Muzzle Velocity | 3,540 fps (1080 mps) |
| Working Pressure | N/A |
| Approximate Barrel Life | 1300-1400 |
| Ammunition stowage per gun | Number of ready rounds: 16 for each barrel Number of rounds stored on mount: 44 rounds for upper barrels, 48 rounds for lower barrels |
| Targets | Distance |
|---|---|
| Max. Ballistic Range | 12,140 yards (11,100 m) |
| Max. Effective Range Against Aircraft | 5,470 yards (5,000 m) |
| Max. Effective Range Against Surface Targets | 10,000 yards (9,140 m) |
| Designation | SM-21-ZIF single mount SM-20-ZIF1 quad mount ZIF-68 quad mount |
|---|---|
| Weight | SM-21-ZIF: 7,936 lbs. (3,600 kg) SM-20-ZIF1: 34,392 lbs. (15,600 kg) ZIF-68: 36,376 lbs. (16,500 kg) |
| Elevation | SM-21-ZIF: -10 / +85 degrees SM-20-ZIF1: -13 / +85 degrees ZIF-68: -13 / +85 degrees |
| Elevation Rate | SM-21-ZIF: 25 degrees per second SM-20-ZIF1: 25 degrees per second ZIF-68: 25 degrees per second |
| Train | M-21-ZIF: 360 degrees SM-20-ZIF1: -200 / +200 degrees ZIF-68: -200 / +200 degrees |
| Train Rate | SM-21-ZIF: 40 degrees per second SM-20-ZIF1: 30 degrees per second ZIF-68: 30 degrees per second |
| Gun recoil | 11 - 14.17 in (281 - 360 mm) |
Data from:
- "Entsiklopedia Otechestvennoi Artillerii" (Encyclopedia of Fatherland [Russian] Artillery) by A.V. Shirokorad
Special help from Vladimir Yakubov