76 mm/45 QF 3in 20cwt (76 mm)

Description

The OQF 3in 20cwt is a British anti-aircraft cannon. Originally seeing use in the Royal Navy prior World War I, the cannon would continue to serve on RN vessels in World War II, as well as a ground-mount on converted Churchill tanks.

Vehicles equipped with this weapon

Ground vehicles

• Gun Carrier (3-in)

Naval vessels

• SGB Grey Fox
• SGB Grey Goose
• ORP Garland
• HMS Valhalla

General info

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Available ammunition

Ground vehicles

Penetration statistics
Ammunition	Type of warhead	Penetration @ 0° Angle of Attack (mm)
		10 m	100 m	500 m	1,000 m	1,500 m	2,000 m
Shot Mk.2	AP	111	109	97	84	73	64
Shell HE	HE	9	9	9	9	9	9

Shell details
Ammunition	Type of warhead	Velocity (m/s)	Projectile Mass (kg)	Fuse delay (m)	Fuse sensitivity (mm)	Explosive Mass (TNT equivalent) (g)	Ricochet
							0%	50%	100%
Shot Mk.2	AP	762	5.67	N/A	N/A	N/A	47°	60°	65°
Shell HE	HE	609	7.26	0	0.1	530	79°	80°	81°

Naval vessels

Penetration statistics
Ammunition	Type of warhead	Penetration @ 0° Angle of Attack (mm)
		100 m	1,000 m	2,000 m	3,000 m	4,000 m	5,000 m
76 mm HE shell	HE	6	6	6	6	6	6
76 mm Mk.I shrapnel	Shrapnel	5	5	5	5	5	5

Shell details
Ammunition	Type of warhead	Velocity (m/s)	Projectile mass (kg)	Fuse delay (mm)	Fuse sensitivity (mm)	Explosive mass (TNT equivalent) (g)	Ricochet
							0%	50%	100%
76 mm HE shell	HE	762	7.26	0	0.1	320	79°	80°	81°
76 mm Mk.I shrapnel	Shrapnel	617	7.94	0	0.1	180	62°	69°	73°

Comparison with analogues

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Usage in battles

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Pros and cons

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History

The Ordnance Quick-Firing 3-inch, 20 centum weight, was the first dedicated anti-aircraft weapon for both the British Army and Royal Navy and saw service during both World Wars. When World War I began in 1914, the British Army had no anti-aircraft guns. This was a mistake as they soon realized, but an understandable one. At the time, aviation was still in its early stages and the field of air defense was still in its infancy. In addition, the British had long relied on the English Channel as a natural barrier to defend their home from enemy forces in Mainland Europe. However, in August 1914, Germany was in control of Belgium and northeastern France, giving them a staging ground to launch air attacks at England. For an interim measure, the Royal Naval Volunteer Reserve manned Vickers 3-inch guns previously mounted on warships. However, the War Office requested a dedicated anti-aircraft weapon based on the 3-inch Vickers, but with a semi-automatic breech for a higher rate of fire. The guns began delivery the same year and were transferred to the Royal Garrison Artillery.

The guns would have their design evolve as the British Army learned more about the new concept of air defense. The original 12-pound rounds were found to be unstable in flight and caused excessive barrel wear so they were replaced with a more accurate 16-pound shell in 1916 which was ideal for use against German Zeppelins and bombers. The guns had to use a two-piece Wilson-Dalby "predictor" to lead their targets accurately along with a properly set detonation fuse. The fuse was a source of trouble for the British as they were slower to develop clockwork fuses like the Germans and instead used powder-burning fuses for airburst rounds with a backup percussion detonator triggered by direct hits. The source of the trouble was the powder-burning fuse which was never intended to be used in a vertically launched round and the burn changed with the air pressure. They also later removed the percussion fuses after it was found that the rounds would injure or kill British soldiers or civilians if they missed the target and returned to the ground.

The British would make other improvements in the design in different marks. The Mark I* had different rifling, the Mark II ditched the semi-automatic action due to problems at higher elevations, and replaced it with a Vickers straight-pull breech. The Mark III switched to a 2-motion screw, the Mark IV had a one-piece barrel with a Welin single-motion breech block instead of an Asbury breech block. The gun was mounted on a two-wheel travelling platform.

By the end of World War I, 257 guns, both mounted in fixed positions or on the beds of British Army trucks such as the American Pierce lorry, were used to defend England from German air raids. 102 guns were deployed on the Western Front beginning in September 1916 on Peerless 4-ton trucks as self-propelled anti-aircraft vehicles. In the 1930s, the carriage design was updated to a four-wheeled sprung trailer platform to replace the obsolete truck mounts and was given newer barrels and gun predictors that could track targets going 400 mph at 25,000 feet. During the inter-war period, the new QF 3.7-inch anti-aircraft gun began production in 1938. However, when World War II started in September 1939, the 3-inch AA still armed the majority of the British Expeditionary Forces instead of the 3.7-inch gun. 500 were still in service at the time the war started and alongside the BEF, they would serve in the RAF regiment, formed to defend British airfields after the disastrous Battle of Crete in 1941, until they got replaced by the Bofors L/60. In 1941, about 100 guns were converted to anti-tank use due to the loss of equipment at the evacuation from Dunkirk, and attempts to mount them on the chassis of the Churchill tank began, creating the Gun Carrier (3-in). Deployed mostly for defending the British Isles from a potential German invasion, the Gun Carrier and QF 3-inch were superseded by the introduction of the QF 17-pounder.

The QF 3-inch was also in service with the Royal Navy during World War I. The first ship to be fitted with this gun was HMS Iron Duke in 1914. It soon became the main anti-aircraft armament for Royal Navy ships through World War I such as the V-class destroyer HMS Valhalla and until 1945 when it began being replaced by the 4 in QF Mark V. However, it would still see service in World War I like its army counterparts. For the Royal Navy, it was mostly mounted on submarines of the S, V, and U-classes and retrofitted on older destroyers of the A-class and I-class. They would also be used to arm smaller boats in the Royal Navy's arsenal such as the steam gunboats (SGB) including SGB Grey Fox and SGB Grey Goose which were designed for coastal forces.

Media

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See also

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External links

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Britain tank cannons
30 mm	L21A1
40 mm	QF 2-pounder
47 mm	Ordnance QF 3-pounder
57 mm	6pdr OQF Mk.III · 6pdr OQF Mk.V
75 mm	OQF Mk.V
76 mm	OQF 3-inch Howitzer Mk I · OQF 3in 20cwt · QF 17-pounder
77 mm	OQF Mk.II
84 mm	20pdr OQF Mk.I
94 mm	28pdr OQF · 32pdr OQF · OQF Mk.II
95 mm	Howitzer, Tank No.1, Mk.I
105 mm	LRF · Royal Ordnance L7A1
120 mm	Ordnance QF Tk. L1A2 · Ordnance BL Tk. L11 · L11A5 · L30A1
165 mm	ORD BL 6.5in L9A1
183 mm	QF L4A1
	Foreign:
25 mm	M242 (USA)
37 mm	M5 (USA) · M6 (USA)
75 mm	M2 (USA) · M3 (USA)
84 mm	kan Strv 81 (Sweden)
105 mm	Sharir (Israel)
120 mm	Rh120 L/55 A1 (Germany)
125 mm	2A46M-5 (Russia)
155 mm	M185 (USA)
	South Africa
20 mm	GI-2
76 mm	GT-4
90 mm	GT-2
105 mm	GT-3 · GT-7 · GT-8
155 mm	G6 L/45