Royal Ordnance L7

Royal Ordnance L7
M68 (American-licenced L7) 105-millimetre (4.1 in) mounted on an M1 Abrams
Type	Tank gun
Production history
Manufacturer	Royal Ordnance Factories
Specifications
Mass	1,282 kg (2,826 lb)
Length	5.89 m (19.3 ft)
Barrel length	52 calibres
Calibre	105 mm
Rate of fire	10 rounds per minute (maximum)

The Royal Ordnance L7 is the basic model of Britain's most successful tank gun. The L7 was a 105 mm L/52 rifled design intended for use in armoured fighting vehicles. It was so successful that it armed not only British post-war designs, but was used almost universally in "the West" as the main armament of almost every main battle tank of the period.

The L7 was developed by Britain's Royal Ordnance Factories to equip British tanks of the postwar (Cold War) period as the successor to the 20 pounder (84 mm) used on Britain's postwar tank—the Centurion.

The L7 was a popular weapon and continued in use even after it was superseded by the L11 series 120 mm rifled tank gun, for some Centurion tanks operating as Artillery Forward Observation and Armoured Vehicle, Royal Engineers (AVRE) vehicles. The L7, and adaptations of it, can be found today as standard or retrofitted equipment on a wide variety of tanks developed during the Cold War. It is also being used as the main armament of the U.S. Army's Stryker-based Mobile Gun System.

History

L7 105 mm tank gun cut model on display at the Deutsches Panzermuseum.

Work on what became the L7 began in the "early 1950s" under Armament Research and Development Establishment at Fort Halstead with the first gun trials in mid-1956. During the Hungarian Revolution of 1956, a Soviet T-54A medium tank was driven onto the grounds of the British embassy in Budapest by the Hungarians. After a brief examination of this tank's armour and 100 mm gun, British officials decided that the 20 pounder was apparently incapable of defeating it. Hence there was a need to adopt a 105 mm gun.

The L7 was specifically designed to fit into the turret mountings of the 20 pounder. This would enable the Centurions to be upgunned with minimum modifications, hence the fleet could be upgraded in a shorter time and at a lower cost.

User trials of the weapon began in 1959. The first tank to be equipped with the L7 was a single uparmoured Centurion Mark 7 in 1959 which was to prove the viability of up-armouring and up-gunning the Centurion. From 1959 onwards existing Centurions were given upgrades with the L7 gun and armour and new builds incorporated the L7 at production. The gun was subsequently adopted by several other nations for their own MBTs, most notably the German Leopard 1 (for which the L7A3 variant was developed), the Japanese Type 74 (produced under license by Japan Steel Works), the Swedish Stridsvagn 103 (as the L74, with a longer barrel and automatic loader), India for its upgraded T-55A, the U.S. M60 series and earliest versions of the M1 Abrams (with the M68), and the Israeli Merkava. In addition, several countries have used the gun to improve the firepower of existing main battle tanks. Derivatives have even been mounted in Warsaw Pact-built T-54 and T-55 tanks in Israel, Egypt and Iraq, and Type 79 tanks in China.

Design

The breech uses a Horizontally-sliding breechblock for loading the fixed cartridge cases. The gun recoils approximately 29 cm (in most applications), automatically opening the breech and ejecting the empty cartridge case as the gun returns to battery from full recoil. The barrel of the L7 is fitted with a bore evacuator approximately halfway down its length. It is eccentrically mounted, which is a key recognition feature.

Specification

• Calibre: 105 mm (4.13 in)
• Cartridge: 105×607 mm R, 105×617 mm R
• Barrel length: 52 calibres
• Weight: 1,282 kg (2,826 lb)
• Length: 5.89 m (19 ft 4 in)
• Rate of fire: 10 rounds per minute (maximum)

Ammunition Available

• APDS
• APERS-T ("Anti-personnel-tracer")
• APFSDS: 1,475 m/s
• Canister
• Dummy
• HE: 1,174 m/s
• HEAT
• HESH: 737 m/s
• Smoke-White phosphorus incendiary
• Target Practice
• Target Practice Discarding Sabot

Variants

U.S. license-built M68A1E4 being fired as part of a Stryker Mobile Gun System

• L7A1

Standard British production variant.

• L7A3

Variant for the (West) German Leopard 1 MBT. The upper rear corner of the breech block reduced in size so gun can be depressed without hitting the turret roof.

• L74

Swedish variant license-built by Bofors with a 62 calibre (6.51 m) barrel used only for the Stridsvagn 103 MBT.

• M68

U.S. built variant for M60 Patton. Uses a round breech with a vertically-sliding breechblock, and a different design of bore evacuator. Also used on the M1 Abrams up until its replacement by the M256 on the M1A1. Used on Israeli tanks up until the Merkava III. Turkish license built versions by MKEK under the designation of M68T for the 90mm armed M48 took place in the 1980s.

• M68A1E4

Variant of the U.S. M68 designed for use on the Stryker MGS, fitted with an automatic loader.

• KM68A1

Republic of Korea Army's licence-produced variant of the American M68 gun. Used on M48A3K, M48A5K and K1 tanks.

• Type 79/81/83

Chinese copies of an L7 supplied by Austria.

• FM K.4 Modelo 1L

Argentine Army's license produced by Fabricaciones Militares in Argentina. Used on the TAM medium tank.

Usage

• Centurion

and derivatives such as Olifant

• EE-T1 Osório
• Leopard 1
• M1 Abrams in early models (the M1 and M1IP models)
• M47 Patton in some upgraded variants (examples: Spanish M47E1 and M47E2)
• M48 Patton in some upgraded variants (M48A5, Israeli-rebuilt M48s, etc.)
• M60 Patton Tank
• M1128 Mobile Gun System
• K1 Type 88
• Merkava I and II
• OF-40
• CM11 Brave Tiger
• Pz-61 & Pz-68
• Stingray light tank
• Stridsvagn 103
• T-54 in several upgraded variants (for example Israeli Tiran-4Sh)
• T-55 in several upgraded variants (for example Egyptian modified T-55s)
• TAM medium tank
• Type 74
• Vickers MBT
• Vijayanta
• Ramses II
• Chinese Type 88 tank.

References

• Zaloga, Steven J. and Hugh Johnson (2004). T-54 and T-55 Main Battle Tanks 1944–2004. Oxford: Osprey. ISBN 1-84176-792-1.
• Starry, Donn A., General. "Mounted Combat In Vietnam." Vietnam Studies. Department of the Army. First printing 1978.
• Hunnicutt, R. P. "Patton: A History of the American Main Battle Tank." 1984; Presidio Press. ISBN 0-89141-230-1.