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QF 13 pounder 9 cwt anti-aircraft gun
Australians watching a 13 pdr 9 cwt anti-aircraft gun, Morbecque, Third Battle of Ypres, August 29, 1917. The neck in the cartridge is visible.
Type Anti-aircraft gun
Place of origin  United Kingdom
Service history
In service 1915 - 1920s[1]
Used by British Empire
Wars World War I
Weight 7.5 tons[2]
Barrel length Bore: 7 feet 9 inches (2.36 m);
Total: 8 feet 1 inch (2.46 m)[2]

Shell 12.5 pounds (5.67 kg) Shrapnel; later HE
Calibre 3-inch (76.2 mm)
Recoil Hydro-spring, constant
24 inches (610 mm) (Mk III mount); 35 inches (889 mm) (Mk IV mount)[2]
Carriage high-angle mounting on lorry
Elevation 0° - 80°[2]
Traverse 360°[2]
Rate of fire 8 rds/min
Muzzle velocity 2,150 ft/s (660 m/s)[3]
Maximum range 19,000 ft (5,800 m)[4]

The 13 pounder 9 cwt anti-aircraft gun became the standard mobile British anti-aircraft gun of the World War I era, especially in theatres outside Britain. 13 pounder referred to the weight of the shell, 9 cwt referred to the weight of the barrel and breech (9 x 112 lb = 1008 lb), to differentiate it from other varieties of "13 pounder".


Earlier anti-aircraft guns based on 13 pounder and 18 pounder guns proved unsatisfactory, primarily due to their low muzzle velocities. On 18 February 1915 Sir John French, commander of the British Expeditionary Force in France, asked for an anti-aircraft gun with a muzzle velocity of 2,000 feet per second (610 m/s).[5] On 19 August 1915 the Army Council proposed adapting existing 18-pounder guns (3.3-inch bore) to use 13-pounder (3-inch) shells, thus meeting the requirement for higher velocity.[6]

This weapon combined an 18 pounder breech and barrel with a liner (sleeve) inserted to reduce the bore from 3.3-inch (84 mm) to 3-inch (76 mm) so that it could fire the slightly smaller 13 pounder shell but still use the larger cartridge and propellant charge of the 18 pounder resulting in a much higher velocity. A slight neck was introduced in the 18 pounder cartridge to hold the slightly narrower 13 pounder shell in place.

The initial Mk III mounting was based on the 13 pounder Mk II anti-aircraft mounting, but proved to be not strong enough for the extra power of the 18 pounder cartridge.

The Mk IV mounting which followed raised the height by 9 inches (230 mm) and increased recoil from 24 to 35 inches (890 mm) and hence relieved the strain on the mounting.[7]

Several guns are known to have been mounted on 2-wheeled high-angle field carriages and deployed on the Italian front. Hogg & Thurston state that they could theoretically be used as anti-aircraft guns, field guns or howitzers, but they were not officially introduced and may have been of an experimental nature.[8] Routledge states that the carriage was improvised because some of 4th AA Group's guns had arrived in Italy without mountings.[9]

Combat use

Gun on Mk IV mount in action at Cambrai, 13 March 1918

As World War I progressed, it was replaced in the home air defence of England (against German heavy bombers) by the more powerful QF 3 inch 20 cwt gun, but continued in all other theatres. It was usually deployed mounted on medium lorries such as the Thornycroft Type J with a speed of 18 miles per hour, in sections of 2 guns.

On the Western Front they were typically used to protect troop columns, airfields, bases, supply dumps and observation balloons.[10]

As important as the raw performance of the gun itself was the new technology being developed to allow fast calculation of aircraft height and predict where it would be when the shell arrived near it. Modern aircraft could fly at over 100 miles per hour and to 20,000 ft (much lower over the battlefield) by 1918, which made the old reliable artillery shooting techniques obsolete. The shell took 10.1 seconds to reach 5,000 ft (1,500 m) fired at 25° above horizontal, 15.5 seconds to reach 10,000 ft (3,000 m) at 40°, 22.1 seconds to reach 15,000 ft (4,600 m) at 55°.[11] Hence the aircraft position had be calculated 10 – 22 seconds in advance and fuzes needed to be set to explode at the correct height.

By the end of World War I, a 13 pounder AA Section was accompanied by 2 Wilson-Dalby Trackers with a rudimentary electronic computer to provide tachymetric prediction, a UB2 rangefinder, a Height/Fuze Indicator (HFI) and an Identification telescope. German fighters countered by attacking at low level - a few hundred feet. AA guns would continue to fire but the shells would then explode over the heads of those they were defending. But it brought attacking aircraft within range of defensive machine guns. Few aircraft were actually directly shot down, each requiring an average 4,000 - 4,500 shells,[12] but guns were often employed in aerial barrages to deny an airspace to aircraft rather than to simply shoot down individually targeted aircraft. Brigadier Routledge notes that "in the BEF [i.e. on the Western Front] stress was laid on long-range deterrent fire; indeed in Fourth Army this was the BRA's stated policy. 'Kills' were therefore less common. Moreover, gun and fighter zones were not separated, as in Britain, and this made set plans for action less workable".[13]

Routledge further comments that in World War I British cooperation between infantry and anti-aircraft sections was generally rudimentary. However, he points out a successful integration in the Allied advance on the Piave in Italy in late 1918, where S and V Batteries of 4th AA group used their 13 pdr 9 cwt guns to provide mobile air and ground fire in close support of infantry. This tactic later became common in World War II.[9]

At the end of World War I, a total of 306 were in service worldwide, 232 of these on the Western Front (out of a total 348 AA guns there).[14]


The following table[15] compares the gun's performance with the other British World War I anti-aircraft guns:-

Gun muzzle velocity (ft/s) Shell (lb) Time to 5,000 ft (1,500 m) at 25° (seconds) Time to 10,000 ft (3,000 m) at 40° (seconds) Time to 15,000 ft (4,600 m) at 55° (seconds) Max. height (ft)[16]
QF 13 pounder Mk III 1600 12.5 ? ? ? 17,000
QF 13 pounder 9 cwt 1990[3] 12.5 10.1 15.5 22.1 19,000
QF 12 pdr 12 cwt 2200 12.5 9.1 14.1 19.1 20,000
QF 3 inch 20 cwt 1914 2500 12.5 8.3 12.6 16.3 23,500
QF 3 inch 20 cwt 1916 2000 16 9.2 13.7 18.8 22,000[17]
QF 4 inch Mk V WWI 2350 31 (3 c.r.h.) 4.4?? 9.6 12.3 28,750
QF 4 inch Mk V WWII[18] 2350 31 (4.38/6 c.r.h.) ? ? ? 31,000

See also

Surviving examples

Restored gun on Mk III mount on Thornycroft lorry, at Imperial War Museum Duxford

Notes and references

  1. Hogg & Thurston state it was declared obsolete in British service in 1921 but continued in service with the Canadian and Dutch armies for several more years
  2. 2.0 2.1 2.2 2.3 2.4 Hogg & Thurston 1972, page 65
  3. 3.0 3.1 Routledge 1994, page 9 quotes muzzle velocity 1,990 feet per second (610 m/s). Hogg & Thurston 1972, page 65 quote 2150 ft/second
  4. Farndale 1986, page 132, 364
  5. History of the Ministry of Munitions, page 26
  6. History of the Ministry of Munitions, page 27
  7. Hogg & Thurston 1972, page 64
  8. Hogg & Thurston 1972, page 66-67
  9. 9.0 9.1 Routledge 1994, page 33
  10. Routledge 1994, page 32
  11. Routledge 1994, page 9
  12. Routledge 1994, page 20, 24, 23
  13. Routledge 1994, page 21
  14. Routledge 1994, page 27
  15. Routledge 1994, Page 9
  16. Hogg & Thurston 1972, Page 234-235
  17. Routledge 1994, Page 13
  18. WWII details from Tony DiGiulian's website
  19. Imperial War Museum (2013). "13 pdr 9 cwt Anti-Aircraft Gun (ORD 103)". IWM Collections Search. Retrieved 10 March 2013. 


  • Official History of The Ministry of Munitions, 1922. Volume X The Supply of Munitions. Part VI Anti-Aircraft Supplies. Facsimile reprint by Imperial War Museum and Naval & Military Press 2007. ISBN 1-84734-884-X
  • General Sir Martin Farndale, History of the Royal Regiment of Artillery. Western Front 1914-18. London: Royal Artillery Institution, 1986. ISBN 1-870114-00-0.
  • General Sir Martin Farndale, History of the Royal Regiment of Artillery : Forgotten Fronts and the Home Base 1914-18. London:The Royal Artillery Institution, 1988. ISBN 1-870114-05-1
  • I.V. Hogg & L.F. Thurston, British Artillery Weapons & Ammunition 1914-1918. London:Ian Allan, 1972. ISBN 978-0-7110-0381-1
  • Brigadier NW Routledge, History of the Royal Regiment of Artillery. Anti-Aircraft Artillery, 1914-55. London: Brassey's, 1994. ISBN 1-85753-099-3

External links

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