Vickers 40 mm Class S gun: Difference between revisions

|caption= 1942. A [[Hawker Hurricane]] fitted with two Vickers S, at [[Heliopolis, Cairo|Shandur]], Egypt.

The '''Vickers 40&nbsp;mm Class S gun''',<ref>{{cite web |title=Vickers Class S |url=http://www.airwar.ru/weapon/guns/class_s.html |website=airwar.ru |access-date=2022-12-20}}</ref>{{efn|The name of the gun is spelled differently throughout sources. Compare with the [[QF 6pdr Class M Mark I with Auto Loader Mk III]].<ref>{{Cite web |title=The 6 pdr 7 cwt and the Molins Gun |first=Anthony G |last=Williams |date= 7 January 2016 |url=https://www.quarryhs.co.uk/Molins.htm |url-status=livedead |access-date=2021-08-14 |website=quarryhs.co.uk |archive-date=21 February 2021 |archive-url=https://web.archive.org/web/20210221185618/https://www.quarryhs.co.uk/Molins.htm }}</ref>|group=Note}} oftenalso shortenedknown simply as the '''Vickers S''' toor '''"S" gun''',<ref name=Goodrum>{{cite book |first= Alastair |last=Goodrum |title= They Spread Their Wings: Six Courageous Airmen in Combat in the Second World War |url=https://books.google.com/books?id=Ps8TDQAAQBAJ&pg=PT23 |page=23 |publisher= The History Press |date=2013|isbn=9780752492179 }}</ref> was a 40&nbsp;mm (1.57&nbsp;in) airborne [[autocannon]] designed by [[Vickers-Armstrongs]] for use as aircraft armament.

It was primarily used during [[World War II]] by British aircraft to attack ground targets.<ref>{{Cite web |first=Anthony G |last=Williams |title=The Vickers 40 mm Class S Gun With Littlejohn Adaptor|url=https://www.quarryhs.co.uk/sgun.htm|url-status=live|access-date=2021-08-14|website=quarryhs.co.uk}}</ref> It was largely replaced by the [[RP-3]] rocket from 1943 on.

The Vickers 40 mm Class S gun was developed in the late 1930s as defensive weapon for bomber aircraft. The [[ammunition]] was based on the 40x158R cartridge case of the 40 mm [[QF 2-pounder naval gun|naval QF 2-pounder anti-aircraft gun]] (known as the "pom-pom"). The gun itself was derived from the [[COW 37 mm gun|Coventry Ordnance Works 37 mm gun]] which used a [[Long recoil#Long recoil operation|long-recoil operation]] to fire a {{convert|1.5|lb|abbr=on}} projectile.

In March 1941, researchers with the [[Fighter Interception Unit]] at [[RAF Tangmere]] fitted the fourth prototype Mk I [[Bristol Beaufighter]] night fighter{{efn|military serial number ''R2055''}} with the Vickers S, installed asymmetrically, in the place of one of the standard 20 mm cannon. In August, the [[Rolls-Royce 40 mm cannon]] ("R" model) was also trialled in the same Beaufighter. Both cannons were assessed when fired in the air and on the ground. In October, the Vickers S was recommended for any future service use, although it was never incorporated into production Beaufighters. The reasons for this have remained unclear, although it may have reflected the perception that a single 40 mm cannon lacked advantages over the 2x204x20 mm configuration. In addition,

[[Hawker Hurricane]]s, fitted with two Vickers S were trialled virtuallythough simultaneouslynot initially adopted in [[North African campaign|North Africa, incampaign]] theas anti-tank role and this concept was also rejectedarmament.{{cn|date=October 2022}}

Early operations by the [[Desert Air Force]] in the North Africa campaign demonstrated that existing weapons were ineffective against newer German vehicles like the [[Panzer III]] medium tank. In April 1941 a group formed to study the issue, considered a series of 37 and 40&nbsp;mm weapons including the "S", the Rolls-Royce cannon ("BF"belt fed variant), and the US-built [[M4 autocannon]], all firing [[armour-piercing]] ammunition.<ref name="Wallace,1972">{{cite book|last=Wallace|first=G.F.|title=The Guns of the Royal Air Force 1939-1945|publisher=William Kimber|location=London|year=1972|isbn=0-7183-0362-8|chapter=10, The 40mm Guns}}</ref>{{page needed|date=October 2022}} The Rolls-Royce "BF" was initially selected, although it used drum-fed ammunition rather than the "S" belt system that was considered more reliable. About 200 BF guns were produced, but after a series of misfires and ammunition explosions,<ref name=Goodrum/>{{page needed|date=October 2022}} the decision was made to introduce [[ground attack]] variants of the Hawker Hurricane]] (designated [[Hawker Hurricane variants#Hurricane IID|Mark IID]]) with the "S". This had the added advantage that it carried 15 rounds of ammunition, compared to the "BF"'s 12.

The weapon was cleared for service on the Hurricane in April 1942 and formed up with [[No. 6 Squadron RAF]] at RAF [[RAFHeliopolis, Cairo|Shandur]] in [[Egypt]] in May. The weapon's champion, Wing Commander [[Stephen 'Dru' Drury]], trained the pilots on using the weapon, as it had so much recoil that the aircraft slowed significantly when fired. This caused the nose to drop, and while flying at a typical altitude of {{convert|50|ft|abbr=on}} during the approach, firing without first re-adjusting the flight path was dangerous. The pilots eventually concluded that the guns could be fired twice before the aircraft flew past the target, although on rare occasions a third shot was possible.<ref name=Goodrum/>{{page needed|date=October 2022}}

Assessments carried out in South East Asia showed a relatively high level of accuracy: an average of 25% of shots fired at tanks hit their target. By comparison, "60 lb" RP-3 rocket projectiles only hit 5% against tank-sized targets. However, 40 mm HE rounds were twice as accurate as AP rounds, possibly because the lower weight and higher velocity of the HE round gave it ballistics similar to that of the .303 in (7.7 mm) [[M1919 Browning machine gun|Browning machine gun]]s that were used for sighting.

== AircraftComparable weapons of comparable role and era ==

;{{flag|Nazi Germany}}

* [[MK 101 cannon|30 mm [[MK 103101]] – automatic anti-tank/anti-bomber gun

*50 [[BK 3,7|37 mm [[BK 53,7]] – automatic anti-tank/anti-bomber gun

*Anthony G Williams, [http://www.quarryhs.co.uk/37-40mm.htm 37MM AND 40MM GUNS IN BRITISH SERVICE] {{Webarchive|url=https://web.archive.org/web/20200203213225/http://quarryhs.co.uk/37-40mm.htm |date=3 February 2020 }}

[[Category:Aircraft gunsartillery]]