Russian
45 mm/46 (1.77") 21-K
Updated 13 May 2006
This gun was developed by taking a standard Army 45 mm Pattern 1932 anti-tank gun and placing it on a navalized mount with a semi-automatic breech.  The gun was tested in 1934 and was accepted into production but manufacturing problems meant that only a quarter of the guns produced prior to 1935 had automatic breech mechanisms.

This weapon was the standard AA mount on Soviet ships until 1941-42 when it began to be replaced by the 37 mm/67 machine gun.  However, it remained in production until 1947.  As an AA gun it had limited effectiveness, due to being only semi-automatic and not having a time fuze, thus requiring a direct hit to destroy a target.

In 1936-37 two new designs for adding AA protection to river monitors were produced.  The 40-K mount was a single 45 mm turreted mount and 41-K was a twin mount.  By the beginning of the war a total of 42 mountings of both types had been supplied to the Navy.

The early gun barrels consisted of having the tube inserted into the casing while hot, while later barrels were monobloc types.  A total of 2,799 guns were made from 1934 to 1947.
WNRussian_45-45_M172_pic.jpg

Russian Submarine M172 (ex-M88)
IWM Photograph
WNRussian_45-45_museum_pic.jpg

45 mm 21-K now at the Central Naval Museum in St. Petersburg, Russia
Photograph copyrighted by Vladimir Yakubov
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Gun Characteristics
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Designation 45 mm/46 (1.77") 21-K
Ship Class Used On almost every Soviet ship built before 1942
Date Of Design 1932
Date In Service 1934
Gun Weight 235.9 lbs. - 253.5 lbs. (107-115 kg)
Gun Length oa 94.37 in (2.3975 m)
Bore Length 81.59 in (2.0725 m)
Rifling Length 65 in (1.650 m)
Grooves 16
Lands N/A
Twist N/A
Chamber Volume 30.5 in3 (0.5 dm3)
Rate Of Fire 25 - 30 rounds per minute
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Ammunition
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Type Fixed
Weight of Complete Round FRAG-Tracer (OT-033) - 4.41 lbs. (2 kg)
HE (O-240) - 6.37 lbs. (2.89 kg)
FRAG-Tracer (OR-73A) - 5.12 lbs. (2.32 kg)
Projectile Types and Weights FRAG-Tracer (OT-033) - 2.35 lbs. (1.065 kg)
FRAG-Tracer (OR-73A) - 3.11 lbs. (1.41 kg)
HE (O-240) - 4.7 lbs. (2.14 kg)
HE (F-73) - 3.11 lbs. (1.41 kg)
AP (BR-240) - 3.13 lbs. (1.42 kg)
Bursting Charge FRAG-Tracer (OT-033) - 0.11 lbs. (52 g)
FRAG-Tracer (OR-73A) - 0.08 lbs. (37 g)
HE (O-240) - 0.26 lbs. (118 g)
HE (F-73) - 0.16 lbs. (74 g)
AP (BR-240) - 0.04 lbs. (18 g)
Projectile Length FRAG-Tracer (OT-033) - 4.3 calibers
FRAG-Tracer (OR-73A) - 4 calibers
HE (O-240) - 5.6 calibers
HE (F-73) - 4.7 calibers
AP (BR-240) - 3.82 calibers
Propellant Charge FRAG-Tracer (OT-033) - 0.93 lbs. (0.42 kg)
HE (O-240) - 0.24 lbs. (0.11 kg)
FRAG-Tracer (OR-73A) - 0.68 lbs. (0.31 kg)
Cartridge weighs 1.32 lbs. (0.6 kg) for all
Muzzle Velocity FRAG-Tracer (OT-033) - 2,890 fps (880 mps)
FRAG-Tracer (OR-73A) - 2,490 fps (760 mps)
HE (O-240) - 1,100 fps (335 mps)
HE (F-73) - 2,490 fps (760 mps)
AP (BR-240) - 2,490 fps (760 mps)
Working Pressure 2650 kg/cm2
Approximate Barrel Life 4000 rounds
Ammunition stowage per gun S-class, D-class, Sch-class, L-XIII class submarines:  500 rounds
P-class submarines: 460 rounds
K-class submarines: 550 rounds
M-class submarines: 195 rounds
M-XV class submarines: 200 rounds
L-II, L-XI class submarines: 250 rounds
Usual surface ship loadout: 500 rounds
40-K and 41-K:  72 rounds in the turret
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Range
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Elevation With 3.11 lbs. (1.41 kg) FRAG-Tracer (OR-73A) Shell
Range @ 45 degrees 10,060 yards (9,200 m)
AA Ceiling @ 85 degrees 19,685 feet (6,000 m)
Elevation With 4.7 lbs. (2.14 kg) HE (O-240) Shell
Range @ 45 degrees 5,470 yards (5,000 m)
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Mount / Turret Data
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Designation Single Mount:  21-K
Single Turret Mount:  40-K 
Twin Turret Mount:  41-K 
Weight  21-K: 1,117.7 lbs. (507 kg)
40-K: about 4,410 lbs. (2,000 kg)
41-K: about 5,730 lbs. (2,600 kg)
Elevation 21-K:  -10 / +85 degrees
40-K and 41-K:  -5 / +85 degrees
Elevation Rate 21-K:  10-20 degrees per second
40-K:  8 degrees per second
41-K:  8 degrees per second
Train 360 degrees
Train Rate 21-K:  10-18 degrees per second
40-K:  4.8-9.8 degrees per second
41-K:  4.8-9.8 degrees per second
Gun recoil 21-K:  10.63 - 11.81 in (27 - 30 cm)
40-K:  10.83 - 12.2 in (27.5 - 31 cm)
41-K:  11.22 - 12.6 in (28.5 - 32 cm)
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Data from
"Naval Weapons of World War Two" by John Campbell
"Sovetskie Boevye Korabli 1941-45: IV Vooruzhnie" (Soviet Warships 1941-45: Volume IV Armament) by A.V. Platonov
"Entsiklopedia Otechestvennoi Artillerii" (Encyclopedia of Fatherland (Russian) Artillery) by A.V. Shirokorad
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Special help from Vladimir Yakubov