View source for QF 2 pounder naval gun

{{about|the anti-aircraft autocannon|the World War II anti-tank gun|Ordnance QF 2 pounder}}
{{Infobox Weapon
|name= QF 2 pdr Mark VIII ("pom-pom")
|image= [[File:Pom pom on HMS Kelvin.JPG|300px]]
|caption= The quadruple 2 pdr mounting (Mk.VII) of [[HMS Kelvin (F37)|HMS ''Kelvin'']]
|origin= {{flag|United Kingdom}}
|type= [[Autocannon]]
<!-- Type selection -->
|is_ranged= yes
|is_bladed=
|is_explosive= yes
|is_artillery= yes
|is_vehicle=
|is_missile=
|is_UK= yes
<!-- Service history -->
|service=1915–1940s (Mk II)<br>1930–1940s (Mk VIII)
|used_by=British Empire,<br>{{JPN}},<br>{{RUS}},<br>{{ITA}}
|wars=[[World War I]]<br>[[World War II]]
<!-- Production history -->
|designer= [[Vickers Armstrongs]]
|design_date=1915 (Mk II)<br>1923 (Mk VIII)
|manufacturer=
|unit_cost=
|production_date=
|number= 
|variants= Low Velocity (LV) & High Velocity (HV),<br />RHI, LHI, RHO, LHO for multiple mountings,<br />Type 91 HI ''Shiki'' (Japanese)
|spec_label=Mk.VIII HV
|weight= 850 lb (385.5 kg)
|length= 102.6 in (2.61 m)
<!-- Ranged weapon specifications --> 
|cartridge= 40 × 158R
|caliber= 40 mm (1.575 in)
|barrels= 1, 4 or 8
|action= 
|rate= 115 rpm
|velocity= 701 m/s, (2,300 ft/s)worn gun
|velocity= 732 m/s, (2,400 ft/s)new gun<ref>Naval Weapons of WW2, Campbell, p71</ref> 
|range= 3,960 m A/A ceiling (13,300 ft)
|max_range= 4,572 m (5,000 yards)
|feed= 14-round steel-link belt
|sights= 
<!-- Artillery specifications -->
|breech=
|recoil=
|carriage=
|elevation=
|traverse=
<!-- Explosive specifications --> 
|filling_weight= 71 g (2.5 oz) 
}}
 

The '''2-pounder gun''', officially designated the '''QF 2-pounder''' ([[British ordnance terms#QF|QF]] denoting "quick firing") and universally known as the '''pom-pom''', was a 1.575&nbsp;inch (40&nbsp;mm) [[United Kingdom|British]] [[autocannon]], used famously as an [[Anti-aircraft warfare|anti-aircraft gun]] by the [[Royal Navy]]. The name came from the sound that the original models were reported to make when firing. Although these were 2-pounder guns, in that they fired a projectile with a weight of 2 [[pound (mass)|pounds]], they were not the same gun as that used by the [[British Army]] as an anti-tank weapon or to equip British tanks and certain [[Armored car (military)|armoured car]]s.

==Predecessors - Boer War and the Great War==
===QF 1 pounder===
{{main|QF 1 pounder pom-pom}}
The first gun to be called a pom-pom was the [[QF 1 pounder pom-pom|37 mm Nordenfelt-Maxim]] or "QF 1-pounder" introduced during the [[Second Boer War]], the smallest artillery piece of that war. It fired a shell one pound in weight accurately over a distance of {{convert|3000|yd|m|sigfig=3}}. The barrel was water cooled and the shells were belt-fed from a 25 round fabric belt. The [[Boer]]s used them against the British, who, seeing their utility, had the design copied by [[Vickers]], who were already producing [[Maxim gun]]s.

In [[World War I]] it was used in the trenches of the [[Western Front]] against aircraft. It was common British practice at this time to refer to artillery by the weight of the projectile rather than the bore of the barrel, e.g. a 3-pounder gun had a calibre of 47&nbsp;mm, a 6-pounder was 57&nbsp;mm etc.

===QF 1½ pounder===
The first naval pom-pom was the QF 1.5-pdr Mark I, a piece with a calibre of 37&nbsp;mm (1.46&nbsp;in) and a barrel 43 [[Caliber_(artillery)|calibre]]s long. This was trialed in the [[Arethusa class cruiser (1913)|''Arethusa'' class]] [[light cruiser]]s [[HMS Arethusa (1913)|HMS ''Arethusa'']] and [[HMS Undaunted (1914)|HMS ''Undaunted'']], but did not enter full service, being replaced instead by a larger weapon, the QF 2-pdr Mark II (see below).

== QF 2-pounder Mark II ==
[[File:2pounderVickersCrewMesopotamia1918Front.jpg|thumb|left|<center>Posed photo of Mk II guarding a train against air attack, [[Mesopotamia Campaign|Mesopotamia]], 1918</center>]]
The '''QF 2-pounder Mark II''' was essentially a scaled-up version of the [[QF 1 pounder pom-pom|QF 1 pounder]] Maxim gun produced by [[Vickers]]. It was a 40&nbsp;mm calibre gun with a water-cooled barrel and a Vickers-Maxim mechanism. It was ordered in 1915 by the [[Royal Navy]] as an anti-aircraft weapon for ships of cruiser size and below. The original models fired from hand-loaded fabric belts, although these were later replaced by steel-link belts. This 'scaling-up' process was not entirely successful, as it left the mechanism rather light and prone to faults such as rounds falling out of the belts.

Surviving weapons were brought out of storage to see service in [[World War II]], mainly on board second-rate ships such as [[naval trawler]]s, Motor Boats and "armed yachts". It was used almost exclusively in the single barrel, unpowered pedestal mountings P Mark II (Royal Navy nomenclature gave mountings and guns their own distinct Mark numbers) except for a small number of weapons on the mounting Mark XV which was a twin-barreled, powered mount. These were too heavy to be of any use at sea and were therefore mounted ashore. All were scrapped by 1944.

* Calibre: 40&nbsp;mm L/39
* Total length: 96&nbsp;inches.<ref name=Hogg&Thurston1972Page28/>
* Length of bore: 62&nbsp;inches<ref name=Hogg&Thurston1972Page28>I.V. Hogg & L.F. Thurston, British Artillery Weapons & Ammunition 1914-1918. London: Ian Allan, 1972, Page 28.</ref>
* Rifling: Polygroove, plain section, 54.84&nbsp;inches, uniform twist 1 in 30&nbsp;inch, 12 grooves.<ref name=Hogg&Thurston1972Page28/>
* Weight of gun & breech assembly: 527&nbsp;lb<ref name=Hogg&Thurston1972Page28/>
* Shell Weight: 2&nbsp;lb (980 g). HE.
* Rate of Fire: 200 rpm
* Effective Range: 1,200 yd (1,000 m)
* Muzzle Velocity: 1920&nbsp;ft/s (585 m/s)

Some 7,000 guns were made. The gun was also used by the [[Japan]]ese as the 40&nbsp;mm/62 "HI" Shiki.

== QF 2-pounder Mark VIII ==
[[File:MkVIIIpompomsHMSRodney1940.jpg|thumb|left|<center>8-barrelled "Chicago piano" on [[HMS Rodney (29)|HMS ''Rodney'']], viewed from below</center>]]
The [[Royal Navy]] had identified the need for a rapid-firing, multi-barrelled close-range anti-aircraft weapon at an early stage. Design work for such a weapon began in 1923 based on the earlier Mark II, undoubtedly to utilise the enormous stocks of 2-pounder ammunition left over from World War I. Lack of funding led to a convoluted and drawn-out design and trials history, and it was not until 1930 that these weapons began to enter service. Known as the '''QF 2-pounder Mark VIII''', it is usually referred to as the ''multiple pom-pom''. The initial mounting was the 11.8 to 17.35 ton<ref>Raven and Roberts, ''British Cruisers of WW2'', p224. The first 8 barrel mounting weighed 11.8 tons while a Remote Power Control mount along with 1.6 tons (1200 rounds) of ammunition weighed 17.35 tons.</ref><ref>Campbell, ''Naval Weapons of WW2'', p67 and p149. Campbell notes that a quad USN Bofors mount weighed 11.12 to 11.88 tons and only carried a maximum of 10 rounds per gun on the mount.</ref>, eight-barrelled mounting Mark V (later Mark VI), suitable for ships of [[cruiser]] and [[aircraft carrier]] size upwards. From 1935 the quadruple mounting Mark VII, essentially half a Mark V or VI, entered service for ships of [[destroyer]] and [[cruiser]] size. These multiple gun mounts required four different guns and were nicknamed the "Chicago Piano"<ref name=Hogg&Thurston1972Page28/>. The mount had 2 rows each of 2 or 4 weapons. Guns were produced in both right and left hand and "inner" and "outer" so that the feed and ejector mechanisms matched. Single barrelled mounts, the Mark VIII (manual) and Mark XVI (power operated), were also widely used, mainly in small escorts (such as the [[Flower class corvette|'Flower' Class corvettes]]) and coastal craft (especially early Fairmile 'D' [[Motor Gun Boat|motor gunboat]]s). The Mark XVI mounting was related to the twin mounting Mark V for the [[Oerlikon 20 mm cannon]] and the "Boffin" mounting for the [[Bofors 40 mm gun]]. An interesting feature was the very large magazine, from 140 rounds per gun for the 8 barrelled mount, to 56 rounds for the single mounts<ref>Campbell, Naval Weapons of WW2, P72</ref>. This large ammunition capacity gave the 8 barrelled mount the ability to fire continuously for 73 seconds without reloading.

An advanced weapon when introduced, by the outbreak of World War II advances in aircraft would have made it obsolete but for the introduction of a high velocity round and new Director designs. It was intended that the curtain of fire it threw up would be sufficient to deter attacking aircraft, which it did but was hampered by the ineffective [[Pom-Pom_Director#The_Pom-Pom_Director_Mark_I_-_III|Mk III director]]<ref name="Campbell p20">Campbell, Naval Weapons of WW2, p20</ref>. The [[Pom-Pom Director|MK IV Director]] with a [[Gyro Rate Unit]] and [[Radar_Type_282#Type_282|Type 282 radar]]<ref>The Gunnery Pocket book, p164</ref> was a great advance and was introduced on the [[King George V class battleship (1939)|KGV class battleship]]s. In January 1941, [[HMS Illustrious (87)|HMS ''Illustrious'']]'s Mk VIII (HV) mountings performed flawlessly firing 30,000 rounds with very few stoppages<ref name="Campbell p20"/>.   When [[HMS Prince of Wales (1939)|HMS ''Prince of Wales'']] was attacked and sunk by [[Japan]]ese aircraft near Singapore the subsequent report judged that a single [[Bofors 40 mm gun|40 mm Bofors]] gun firing tracer was a more effective anti-aircraft weapon<ref>Middlebrook, ''Battleship'', p340. The report does not note any 40mm Bofors kills or even hits from the Prince of Wales' Bofors gun, while hits from pom-pom fire were recorded by the crew of the Prince of Wales.</ref><ref>Middlebrook, ''Battleship'', p340: "''It is considered that a Bofors with tracer ammunition in local control is a more valuable weapon than an 8 barrelled pom-pom in director control without tracer...''"</ref> than a multiple pom-pom in Director control, as the pom-poms did not have tracer ammunition and the pom-pom ammunition had deteriorated badly in their ready use lockers, while the Type 282 radar units also failed in the equatorial heat<ref>Brown, ''A radar history of World War II: technical and military imperatives'', p220. Brown notes that 3 out of 4 type 282 radars were out of service when Prince of Wales departed Singapore.</ref><ref>Garzke and Dulin, ''Allied Battleships'', p204, notes that the remaining type 282 and two type 285 radars failed after the first torpedo hit.</ref>. In the same action, the Commissioned Gunner of [[HMS Repulse (1916)|HMS ''Repulse'']] spent the whole action running from one pom-pom mount to another trying to keep them operational due to the faulty ammunition. The pom-poms on Repulse shot down 2 of the four confirmed kills made by Force Z<ref>Middlebrook, ''Battleship'', p224</ref>, while Prince of Wales' pom-poms did record hits on enemy aircraft<ref>Middlebrook, ''Battleship'', p340</ref>. The Royal Navy judged the pom-pom's effectiveness to range from about half that of the Bofors, per gun, against torpedo planes to about equal against Kamikaze attackers.<ref>Campbell, ''Naval Weapons of WW2'', P67: "''...if control and mountings were of equal efficiency, the Bofors was reckoned to be twice as effective as the pom-pom against torpedo planes but not much better against very close range targets such as Kamikazes.''"</ref>  It was a ubiquitous weapon that was never entirely displaced by the Bofors gun during World War II and shot down many Axis aircraft. Later innovations such as remote power control (RPC) coupled to a radar-equipped tachymetric (speed predicting) director increased the accuracy enormously and problems with the fuses and reliability were also remedied. The single mountings received a reprieve towards the end of the war as the 20&nbsp;mm Oerlikon guns had insufficient [[stopping power]] to counter Japanese [[Kamikaze]] aircraft and there were insufficient numbers of Bofors guns to go round.

* Calibre: 40&nbsp;mm L/39
* Shell Weight: 2&nbsp;lb. (980 g) or 1.8&nbsp;lb. (820 g) for High-Velocity ('''HV''') round
* Rate of Fire: 115 rpm fully automatic
* Effective Range: 3,800 yards (3,475 m) or 5,000 yards (4,572 m) HV
* Effective Ceiling (HV): 13,300 feet (3,960 m)
* Muzzle Velocity: 1,920&nbsp;ft/s (585 m/s) or 2,300 feet/s (worn gun) (701 m/s)(new gun MV = 2400&nbsp;ft/s) for HV <ref>Campbell,''Naval Weapons of WW2'', p71</ref>

For more extensive technical data see [http://www.navweaps.com/Weapons/WNBR_2pounder_m8.htm 2-pdr Mark VIII at Navweaps.com]

== QF 2-pounder Mark XIV ==

The '''QF 2-pounder Mark XIV''', or '''Rolls 2 pounder''', was developed by [[Rolls-Royce Limited|Rolls-Royce]] as a competitor to the [[Vickers S|40 mm "Vickers S" gun]] as an aircraft weapon. The latter was the more successful design, and found some use as an anti-tank weapon. A reworked version was adopted by the Royal Navy as a weapon for [[Motor Gun Boat]]s, being adopted in the [[Fairmile C motor gun boat|Fairmile C]] type. It had a semi-automatic horizontally sliding [[breech-loading weapon|breech block]], and was shipped on a manually trained pedestal  mount.  The weapon was not a success, and of the 1,200 ordered only some 600 were delivered. It was replaced by the [[Ordnance QF 6-pounder|Molins 6-pounder gun]], the [[British Army]]'s Ordnance QF 6 pounder gun (57&nbsp;mm) with an auto-loader.

==See also==
*[[QF 1 pounder pom-pom]]
*[[List of anti-aircraft guns]]

==Notes and references==
{{reflist}}

==External links==
{{Commonscat|QF 2 pounder pom-pom}}
* [http://hnsa.org/doc/br224/part4.htm#par473 THE 2-PDR. MARK VIII GUN ON THE MARK VII MOUNTING. in The Gunnery Pocket Book, B.R. 224/45, 1945] placed online courtesy of Historic Naval Ships Association
*Tony DiGiulian, [http://www.navweaps.com/Weapons/WNBR_2pounder_m2.htm British 2-pdr (4 cm/39 (1.575")) Mark II]
*Tony DiGiulian, [http://www.navweaps.com/Weapons/WNBR_2pounder_m8.htm Britain 2-pdr (4 cm/39 (1.575")) Mark VIII]
*Tony DiGiulian, [http://www.navweaps.com/Weapons/WNJAP_40mm-62_HI.htm Japanese 40 mm/62 (1.575") "HI" Type 91]
*Anthony G Williams, [http://www.quarry.nildram.co.uk/37-40mm.htm 37MM AND 40MM GUNS IN BRITISH SERVICE]
* [http://www.britishpathe.com/record.php?id=81593 Convoy to Malta; video footage of the pom pom in action.]
* [http://www.britishpathe.com/record.php?id=23061 Malta Convoy; more video and audio footage of the pom-pom in action.]
*[http://www.britishpathe.com/record.php?id=23105 Newsreel video of HMS Scylla's quad pom-pom fighting the Luftwaffe while protecting convoy PQ18]

{{GreatWarBritishWeapons}}
{{GreatWarBritishNavalWeapons}}
{{WWIIBritishCommNavalWeapons}}

[[Category:World War II anti-aircraft guns]]
[[Category:Naval anti-aircraft guns]]
[[Category:World War I anti-aircraft guns]]
[[Category:World War I artillery of the United Kingdom]]
[[Category:40 mm artillery]]
[[Category:Vickers]]
[[Category:Naval guns of the United Kingdom]]
[[Category:Automatic cannons]]

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