3.7 cm SK C/30

The 3.7 cm SK C/30^{[Note 1]} was the German Kriegsmarine's primary 3.7 cm (1.5 in) anti-aircraft gun during the Second World War. It was superseded by the fully automatic 3.7 cm FlaK 43 late in the war.

3.7 cm SK C/30
3.7 cm SK C/30 on a Dopp L C/30 stabilized mount
Type	Anti-aircraft cannon
Place of origin	Nazi Germany
Service history
In service	1935–1966
Used by	Nazi Germany Spain
Wars	Second World War
Production history
Designer	Rheinmetall
Designed	1930–1935
Manufacturer	Rheinmetall
Produced	1935–1943
Variants	3.7 cm SK C/30U
Specifications
Mass	243 kilograms (536 lb)
Length	3.074 metres (10 ft 1 in)
Barrel length	2.962 metres (9 ft 9 in) L/83
Shell	fixed, cased charge
Shell weight	0.68 kilograms (1 lb 8 oz)
Caliber	37 x 380 mm R
Action	single-shot
Breech	semi-automatic, vertical sliding-block
Elevation	depends on the mount
Traverse	360°
Rate of fire	30 rpm (practical)
Muzzle velocity	1,000 m/s (3,300 ft/s)
Effective firing range	2,000 m (6,600 ft) (effective ceiling)
Maximum firing range	8,500 m (9,300 yd) at 37.5°

Description

The C/30 was a semi-automatic anti-aircraft gun (ie; after firing each round, the breech opened and the spent cartridge casing was automatically expelled, ready for the next round to be loaded), and it was hand-loaded one round at a time. This mechanism gave the weapon an effective, sustained, firing rate of 30 rounds per minute. Whilst not uncompetitive with contemporary and earlier designs of semi-automatic light gun, it was far inferior to the 120 rpm cyclic firing rate of its (slightly later-designed) wartime contemporary, the fully automatic Bofors 40 mm anti-aircraft gun. The C/30's muzzle velocity was, on the other hand, about 12-15% higher than the Bofors; this slightly eased the aiming. The SK C/30U gun was modified for use by submarines. All mountings were suitable for use against both air and soft surface targets.^[1]

Ship classes that carried the 3.7 cm SK C/30 include:

• Admiral Hipper-class cruisers
• Bismarck-class battleships
• Chamois-class minesweeping sloops
• Deutschland-class battleships
• Deutschland-class cruisers
• Elbing-class torpedo boats
• F-class escort ships
• German Type IXA submarines
• German Type XIV submarines
• Graf Zeppelin-class aircraft carriers
• Königsberg-class cruisers
• Leipzig-class cruisers
• M-class minesweepers
• PA-class patrol ships
• R boats
• Sperrbrecher
• Scharnhorst-class battleships
• Type 1934A-class destroyers
• Type 1936-class destroyers
• Type 1936A-class destroyers
• Type 1936B destroyers
• Type 35 torpedo boats
• Type 37 torpedo boats

Mountings

SK C/30U on a type IX U-Boat (U-103) in 1939

The Doppellafette C/30 (Dopp L C/30) was a twin mount with each gun in a separate cradle. It had a six-man crew on the mount itself plus additional ammunition handlers. The mounting was manually traversed and elevated and was gyro-stabilized up to a limit of 19.5° degrees to counteract the roll and pitch of the ship. Most German ships, fleet torpedo boat or larger, carried at least one Dopp L C/30 mounting. The Einheitslafette C/34 (Einh L C/34, universal mounting model 34) was a single gun mounted on a pedestal with a two-man crew. Some mounts were fitted with a 8-millimetre (0.31 in) gun shield. It was used on the smaller Kriegsmarine ships like the Schnellboot. A number were used on land to supplement the anti-aircraft defenses of ports. The Ubts L C/39 submarine mount used the SK C/30U gun. It was a simple pedestal mount with a two-man crew, one of whom trained the gun with the shoulder stirrup; the other used gears to elevate the gun.^[2]

Mounting	weight	elevation
Dopp L C/30	3,670 kg (8,090 lb)	-9° to +85°
Einh L C/34	1,860–2,020 kg (4,100–4,450 lb)	-10° to +80°
Ubts L C/39	1,450 kg (3,200 lb)	-10° to +90°

Ammunition

The SK C/30 used two types of tracer rounds. The 3.7 cm Br Sprgr Patr 40 L/4.1 Lh 37M was a high-explosive round with an incendiary filling while the 3.7 cm Sprgr Patr 40 L/4.1 Lh 37 lacked the incendiary fill, but was otherwise identical. Tracers were available in red, yellow or white and were marked on the shell by a painted band of the appropriate color. A complete round weighed 1.78 kilograms (3.9 lb).^[3]

Comparison of anti-aircraft guns

Country	Gun Model	RPM	Projectile Weight	Weight of fire
Nazi Germany	3.7 cm SK C/30	30	.74 kg (1.6 lb)[4]	22.2 kg (49 lb)
France	Canon de 37 mm Modèle 1925	15–21	.72 kg (1.6 lb)[5]	10.8–15.12 kg (23.8–33.3 lb)
Italy	Cannone-Mitragliera da 37/54 (Breda)	60–120	.82 kg (1.8 lb)[6]	49.2–98.4 kg (108–217 lb)
United States	37 mm Gun M1	120	.87 kg (1.9 lb)	104.4 kg (230 lb)
Nazi Germany	3.7 cm Flak 18/36/37/43	150	.64 kg (1.4 lb)[7]	96 kg (212 lb)
Soviet Union	37 mm automatic air defense gun M1939 (61-K)	80[8]	.73 kg (1.6 lb)[9]	58.4 kg (129 lb)
United Kingdom	QF 2-pounder naval gun	115	.91 kg (2.0 lb)[10]	104.6 kg (231 lb)
Sweden	Bofors 40 mm gun	120	.9 kg (2.0 lb)[11]	108 kg (238 lb)

Footnotes

1. SK - Schnelladekanone (quick loading cannon); C - Construktionsjahr (year of design)