Russian
45 mm/68 (1.77") 21-KM
Updated 13 May 2006
In 1942 the Army switched to the longer barreled 45mm model 1942 AT gun.  The Naval version of this gun was designated 21-KM and was 68 calibers long.  As an AA gun it had limited effectiveness, due to being only semiautomatic and not having a time fuze, which meant that it needed to make a direct hit in order to destroy a target.  Used the same ammunition as the earlier 45 mm/46 21-K.

Used a monobloc barrel.  A total of 1,209 guns were made.
WNRussian_45mm-68_pic.jpg

45 mm/68 on display
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Gun Characteristics
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Designation 45 mm/68 (1.77") 21-KM
Ship Class Used On Many warships 1942 - 1947
Date Of Design 1942
Date In Service 1942
Gun Weight 346.1 lbs. (157 kg)
Gun Length oa 134.33 in (3.412 m)
Bore Length 121.54 (3.087 m)
Rifling Length 104.72 in (2.660 m)
Grooves N/A
Lands NA
Twist N/A
Chamber Volume N/A
Rate Of Fire up to 40 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) - 3,180 fps (970 mps)
FRAG-Tracer (OR-73A) - 2,740 fps (835 mps)
HE (O-240) - 1,125 fps (343 mps)
HE (F-73) - 2,740 fps (835 mps)
AP (BR-240) - 2,740 fps (835 mps)
Working Pressure N/A
Approximate Barrel Life 4,000 rounds
Ammunition stowage per gun Usual surface ship loadout: 500 rounds
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Range
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Elevation With 3.11 lbs. (1.41 kg) FRAG-Tracer (OR-73A) Shell
Max. Ballistic Range 11,680 yards (10,680 m)
AA Ceiling @ 85 degrees 21,000 feet (6,400 m)
Elevation With 4.7 lbs. (2.14 kg) HE (O-240) Shell
Max. Ballistic Range 5,680 yards (5,194 m)
Elevation With 2.35 lbs. (1.065 kg) FRAG-Tracer (OT-033) Shell
Max. Timer Range 6,340 yards (5,800 m)
Note: Max effectve range was 4,000 m vs both surface and air targets.
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Mount / Turret Data
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Designation 21-KM Single Mount
Weight  21-KM:  1911.4 lbs. (867 kg)
Elevation -10 / +85 degrees
Elevation Rate 15 degrees per second
Train 360 degrees
Train Rate 15 degrees per second
Gun recoil 10.83 - 12.4 in (275 - 315 mm)
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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