Russian 45 mm/78 (1.77") SM-7

Russia
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

Ammunition .

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

Range .

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