45 mm/78 (1.77") SM-7
Updated 18 July 2006

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.


SM-20 Quad Mount

Gun Characteristics
Designation 45 mm/78 SM-7
Ship Class Used On 45 mm/78 SM-21-ZIF
   SO-1 (Pr. 201) class, Sasha (Pr. 265) class, base minesweepers and other ships

45 mm/78 SM-20-ZIF1
   Neustrashimyi (NATO Tallinn) (Pr. 41), Kotlin (Pr. 56) class, Bravyi (NATO SAM-Kotlin) (Pr. 56K)
   Bedovyi (Pr. 56EM) DDs, Sovetsky Soyuz (Pr. 24) class BBs (uncompleted)
   Stalingrad (Pr. 82) class BCs (uncompleted), Lenin (Pr. 90) Nuclear Icebreaker (never installed)

45 mm/78 ZIF-68-1
   Pr. 68bis-ZIF cruisers (uncompleted)

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
Elevation With 3.11 lbs. (1.41 kg) HE Shell
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)

Mount / Turret Data
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 SM-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 by Vladimir Yakubov