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Royal Ordnance L11

The Royal Ordnance L11A5, officially designated Gun, 120 mm, Tank L11,[i] is a 120 mm L/55 rifled tank gun design. It was the second 120 mm calibre tank gun in service with British Army. It was the first of NATO's 120 mm main battle tank guns which became the standard calibre for Western tanks in the later period of the Cold War. A total of 3,012 of the L11 guns were produced by 2005. The list price was US$227,000 in 1990.[1]

The L11 was developed by Britain's Royal Ordnance Factories to equip the Chieftain tank as the successor to the 105 mm L7 gun used in the Centurion tank and the heavy Conqueror tank. It was also used on the Challenger 1, which replaced the Chieftain in British and Jordanian service. The weapon has been superseded by the L30 series 120 mm rifled tank gun.

History

The Royal Armament Research and Development Establishment at Fort Halstead designed a new 120 mm rifled tank gun in 1957. The new gun was deemed to be necessary because the British Army specified engagement ranges greater than those of other armies, for example 2,000 m (2,200 yd), as specified by the US Army, despite studies at the time that suggested engagement ranges were below those of the US Army requirements in the great majority of cases.[2] The L11 was specifically designed to fit into the turret mountings of the Chieftain tank (FV4201). After firing trials in 1961, the L11 was accepted for service on the Chieftain in 1965 and entered service with the British Army in 1966.

The adoption of a rifled tank gun on the Challenger led to some controversy, and some experts later urged the British Army to retrofit the turret to fit the smoothbore Rheinmetall Rh-120 adopted by the German Leopard 2 and American M1A1 Abrams. This would allow the British to fire 120 mm APFSDS rounds, which were then in use by the Germans and Americans. The British Army argued the modifying the turret would be impractical and that a smoothbore gun could not fire HESH rounds. Polish-British tank historian Richard Ogorkiewicz argued that the later concern was unwarranted. In the mid 1980s the British Army adopted an "operational emergency" APFSDS round.[3]

During Operation Granby an L11 on a British Army Challenger 1 scored the longest tank-to-tank "kill" in military history, when it destroyed an Iraqi T-55 at a range of 4.7 km (2.9 miles) with an L23 "Fin" round.[4][5]

Since its introduction, the L11 has evolved into eight production versions. In June 1976, development of new ammunition for the L11A5 was begun.

Production models

The Royal Ordnance basic L11 design was developed into a series of improved production models; the L11A5 was the major production version.

Design

The breech mechanism is a downward sliding semi-automatic breechblock. The gun was equipped with a hydro-pneumatic recoil system using two buffers. The gun recoils 37 cm (15 in) in most applications. This breechblock design was based on the breechblock on the Krupp/Skoda sFH 18/43 model 18 that the British studied extensively after the Second World War and perfected for use in the 120 mm gun.[6]

Unlike most Western tank weapons which fire a single fixed round, the projectile and propellant are loaded separately. And unlike the Soviet 125-mm 2A46, the propellant is in the form of a combustible bagged charge (or later, a combustible charge case for armour-piercing rounds). This required the obturation to be provided by rings in the breech rather than the cartridge case, as in fixed rounds and 125 mm separate-loaded ones.

When first introduced, APDS (armour-piercing discarding sabot) rounds were fired using a cylindrical charge. High explosive squash head (HESH), smoke and other rounds used a hemi-cylindrical (i.e. a cylinder sliced in two lengthways) charge (the L3). Two HE charges could therefore be stowed in the same space as one AP charge. In the Chieftain and Challenger tanks, the charges were stored in 36 recesses surrounded by water jackets, so that a hit which penetrated the fighting compartment would rupture the jacket and drench the propellant, preventing a catastrophic ammunition fire (known colloquially as a "brew-up").

The barrel of the L11A5 is fitted with a bore evacuator approximately two-thirds of the way to the muzzle and a thermal sleeve.

When first introduced, a 12.7 mm (.50 in) calibre ranging gun was fitted over the barrel of the L11. The projectiles for this ballistically matched those for HESH rounds fired from the main armament out to 2,600 m (2,800 yd), at which point the tracer element burned out. Starting in 1971 a Barr & Stroud LF2 "Tank Laser Sight" (TLS) laser rangefinder replaced the ranging MG in British service, and in conjunction with the "Muzzle Reference System" (MRF)[ii] added in 1975, allowed engagements at ranges out to 5,000 meters. Further improvement in gunnery performance came with the adoption of the Marconi "Improved Fire Control System" (IFCS) fitted to the Chieftain in 1979.[iii]

Specification

Ammunition

Service ammunition

Prototypes ammunition

Operators

Map with L11A5 operators in blue with former operators in red

Current operators

Former operators

See also

Weapons of comparable role, performance and era

Notes

  1. ^ sometimes abbreviated "Tk"
  2. ^ The Muzzle Reference System uses a laser beam reflected from a mirror at the muzzle to measure minute dimensional changes in the barrel due to temperature, humidity, etc., which are then compensated for in the Fire Control System. The thermal sleeve had originally been developed to minimise such dimensional changes in the barrel which have an increasing effect on gun accuracy as ranges are increased.
  3. ^ Testing at the US Army Aberdeen Proving Ground concluded that engaging targets beyond 3 km (1.9 mi) is not practical due to round deviation.[citation needed] This is especially true against targets that are moving. However see note about 5.1km "kill" in Operation Granby.

References

  1. ^ a b Forecast International. "L11 and L30 120mm Tank Gun". Archived from the original on 10 November 2013.
  2. ^ Ogorkiewicz, p. 50.
  3. ^ Ogorkiewicz, Richard (2015). Tanks: 100 Years of History. Osprey Publishing. pp. 184–185. ISBN 9781472806703. Retrieved 16 August 2024.
  4. ^ "Desert Storm Part 22: Charge of the Heavy Brigade". British Army Official Blog. 28 February 2016. Retrieved 27 December 2016.
  5. ^ "Desert Storm Part 24: Back to Germany". British Army Official Blog. 11 March 2016. Retrieved 27 December 2016.
  6. ^ Hogg, Ian V. The Guns 1939-45. p. 51, para. 3.
  7. ^ Gander, Terry; Hogg, Ian (1 December 1993). Jane's Ammunition Handbook 1994-95. Jane's Information Group. p. 160. ISBN 978-0710611673.
  8. ^ Pengelley, Rupert (8 January 2001). "New projectile for Challenger 2". janes.com. Retrieved 10 March 2022.
  9. ^ "President's Letter 03/00: Safety Precautions for Operating with Depleted Uranium (DU) Tank Ammunition" (PDF). Bristol: Ordnance Board. 23 June 2000. Retrieved 22 March 2020 – via whatdotheyknow.com.
  10. ^ Taylor, Dick (24 September 2015). Challenger 1 Main Battle Tank 1983-2001 Fv 4030/4 Model Owners' Workshop Manual. J H Haynes & Co Ltd. p. 160. ISBN 978-0857338150.
  11. ^ "Jane's".
  12. ^ "Improved Chieftain for Iran". International Defense Review. 4 (4): 98. August 1976.
  13. ^ "120 mm BAE Systems, Global Combat Systems - Munitions, UK tank gun ammunition". 39.107.233.64:8413/zbbd/index. Retrieved 13 August 2022.
  14. ^ "Budget cuts and environmental concerns put UK depleted uranium upgrade out of the picture". bandepleteduranium.org. ICBUW. 18 January 2011. Archived from the original on 19 October 2019. Retrieved 22 March 2020.

Works cited

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