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.
| 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 |
| 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) All cartridges: 1.32 lbs. (0.6 kg) |
| 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 |
| Elevation | Distance |
|---|---|
| 45 degrees | 10,060 yards (9,200 m) |
| AA Ceiling @ 85 degrees | 19,685 feet (6,000 m) |
| Elevation | Distance |
|---|---|
| 45 degrees | 5,470 yards (5,000 m) |
| 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) |
"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
13 May 2006 - Benchmark
17 December 2018 - Converted to HTML 5 format, minor changes