The 120 mm L11 tank gun traces its origins back td the 1950s, and the first firing trials took place during 1961. Breech obturation is obtained by the use of an expanding steel ring on the face of the breech block. The current service version is the L11A5 used on the Challenger 1 and Chieftain which is manually loaded, although trials have taken place using automatic feed devices, none of which have been produced for service.

The 120 mm L11 uses a large'.vertical sliding breech block with an integral vent tube magazine'for firing the propellant charges. The barrel is of a one-piece construction with a bore evacuator two-thirds of the way to the muzzle. Normally, a thermal sleeve is fitted around the barrel. Gun recoil is usually of the orqler of 370 mm and is controlled by two1hydraulic buffers and a hydropneumatic buffer recuperator which dissipate the recoil energy and return the gun to the run-out position J A semi-automatic cam opens the breech after firing ready for reloading. Late production versions of the L11 have provision for a muzzle reference sight over the muzzle.

In British Army service, the 120 mm L11 tank gun installed in the Challenger 1 and Chieftain was to have been replaced by the L30. These plans were abandoned some years ago and the Chieftain MBT was finally phased out of service with the British Army early in 1996. As the Challenger 2 MBT enters service with the British Army the older Challenger 1 MBTs armed with the 120 mm L11 gun will be phased out of service. Early in 1999 it was stated that Jordan would take delivery of a quantity of Challenger 1 MBTs.

• L11A1

Only 130 produced.

• L11A2

Numerous improvements introduced, including breech block interlock and obturator insert indicator.

Changes to this version included an actuating shaft stop, changes to the tube vent filling, alterations to the fire channel dimensions, an obturator sleeve protector, the introduction of a 15-vent tube magazine, and an increase in the strength of the breech ring material.

• L11 A3

Projectile stop removed and design changes to the breech ring.

• L11A4

Not issued.

• L11A5

Introduction of forged upstand for Muzzle Reference Sight and a reduced volume and diameter fume extractor of less weight. These two introductions necessitated the fitting of 7.7 kg of weights for balance purposes. This variant includes a semi-automatic plunger fitted to the vent tube loader.

• L11A6

Conversion of L11A3 using retrofit shrunk

sleeve for Muzzle Reference Sight. New lightweight

fume extractor also fitted involving 2 kg of balance

weights.

• L11A7

Proposed variant of L11A5 with an automatic

vent tube loader.

Production as required. Installed on Chieftain MBT; Challenger 1 MBT; Khalid MBT.