45 mm/46 21-K (45 mm)

Description

The 45 mm/46 21-K is a Soviet anti-aircraft gun derived from the 20-K tank gun. It is equipped on a number of Soviet coastal and bluewater vessels.

Vehicles equipped with this weapon

General info

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Available ammunition

OR-73A HET - Stock HE shell, has low explosive mass and should be replaced quickly
O-240 HE - Researchable HE shell, has more than 3 times the explosive mass of the stock but very low velocity, effective at boats in close-range
BR-240 - APHE shell, useful against armoured targets like armoured gunboats and turrets that HE shells can't penetrate
F-73 - Base-fuze HE shell, effectively acts like an APHE shell with larger explosive mass, is quite effective at dealing damage against ship modules as it penetrates the hull

Penetration statistics
Ammunition	Type of warhead	Penetration @ 0° Angle of Attack (mm)
Ammunition	Type of warhead	100 m	1,000 m	2,000 m	3,000 m	4,000 m	5,000 m
OR-73A HET	HE	3	3	3	3	3	3
O-240 HE	HE	5	5	5	5	5	5
BR-240	APHE	75	55	38	27	20	15
F-73	HE	20	15	10	7	5	4

Shell details
Ammunition	Type of warhead	Velocity (m/s)	Projectile mass (kg)	Fuse delay	Fuse sensitivity (mm)	Explosive mass (TNT equivalent) (g)	Ricochet
Ammunition	Type of warhead	Velocity (m/s)	Projectile mass (kg)	Fuse delay	Fuse sensitivity (mm)	Explosive mass (TNT equivalent) (g)	0%	50%	100%
OR-73A HET	HE	760	1.41	0	0.1	56.98	79°	80°	81°
O-240 HE	HE	335	2.14	0	0.1	181.72	79°	80°	81°
BR-240	APHE	760	1.42	1 m	1.5	27.72	47°	60°	65°
F-73	HE	760	1.41	0.015 s	0.1	113.96	79°	80°	81°

Comparison with analogues

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Usage in battles

Much like in real life, the 21-K is horrible at its intended role, anti-aircraft. Its low rate of fire means it is only effective at hitting aircraft when massed, like on Maxim Gorky. On ships with few mounts like Frunze, the 21-K is essentially useless at shooting down aircraft, but it can be used as a weapon against small boats, where its HE shells can be effective at destroying them.

Pros and cons

Pros:

Can destroy aircraft in one hit
Somewhat effective at fighting small boats with HE and base-fused HE shells

Cons:

Terrible anti-aircraft ability due to low rate of fire

History

The 21-K is a naval derivative of the Soviet 20-K tank cannon. More specifically, both guns share the same progenitor, the 19-K 45 mm anti-tank gun model 1942, a scaled-up variant of a gun from Rheinmetall. The modification for use as a naval anti-aircraft gun was a simple matter of replacing the carriage with a pedestal mount and giving the gun a semi-automatic breech, though when production began in 1934, only a quarter of the guns had this breech. The early guns were older built-up gun designs, but they would be replaced with monobloc barrels later in production. Because it was semi-automatic, the gun struggled compared to the autocannons used by other nations. It also suffered from not having a time fuse, meaning it could only destroy aircraft with a direct hit. In 1936-37, a new mount for the 21-K was created for use on river monitors called the 40-K along with the 41-K which was a twin-mount. 42 of both mounts were ultimately built. 2,799 guns were built in total from 1934 until 1947, though by 1941 it was largely superseded by the smaller, automatic 70-K as the Soviet Navy's main anti-aircraft gun. In 1942, production was switched to the upgraded 21-KM.

Media

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External links

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topic on the official game forum;
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USSR naval cannons
20 mm	ShVAK
25 mm	2M-3
30 mm	AK-230 · 30 mm/54 AK-630 · 30 mm/54 AK-630M · BP "Plamya"
37 mm	37 mm/67 70-K · V-11
45 mm	45 mm/46 21-K · 45 mm/68 21-KM · 45 mm/89 SM-20-ZIF · 45 mm/89 SM-21-ZIF
57 mm	AK-725
75 mm	75 mm/50 Canet patt.1892
76 mm	34-K · 39-K · 76 mm/60 AK-176M · AK-726 · D-56TS · F-34 · Lender AA gun, pattern 1914/15
85 mm	85 mm/52 92-K · 85 mm/54.6 ZIS-C-53 · 90-K
100 mm	100 mm/56 B-34 · 100 mm/70 SM-5-1 · Minizini
102 mm	Pattern 1911
120 mm	120 mm/50 pattern 1905
130 mm	130 mm/55 pattern 1913 · 130 mm/58 SM-2-1 · B-13
152 mm	152 mm/57 B-38
180 mm	180 mm/57 B-1-P · 180 mm/60 B-1-K
305 mm	12-inch/52 pattern 1907 · 305 mm/54 B-50
356 mm	14-inch/52 pattern 1913 (356 mm)
	Foreign:
40 mm	2pdr QF Mk.IIc ^(Britain) · Skoda ^{(Czechoslovakia)}
47 mm	3 pdr QF Hotchkiss ^(Britain)
76 mm	76 mm/40 Ansaldo mod.1917 ^(Italy)
88 mm	SK C/30 ^(Germany)
120 mm	120 mm/50 Mk.4 Bofors M1924 ^(Sweden) · 120 mm/50 O.T.O. Mod.1933 ^(Italy)
152 mm	152/53 mm O.T.O. Mod.1929 ^(Italy)
320 mm	320 mm/44 Ansaldo model 1934 ^(Italy)