The Rheinmetall Rh-120 is a 120 mm smoothbore tank gun designed and produced in former West Germany by the Rheinmetall Waffe Munition GmbH company. It was developed in response to Soviet advances in armour technology and development of new armoured threats. Production began in 1974, with the first version of the gun, known as the L/44 as it was 44 calibres long, used on the German Leopard 2 tank and soon produced under license for the American M1A1 Abrams and other tanks. The L/44 gun has a length of , and the gun system weighs approximately .
By 1990, the L/44 was not considered powerful enough to defeat future Soviet armour, which stimulated an effort by Rheinmetall to develop a better main armament. This first involved a tank gun named Neue Panzerkanone 140 ('new tank gun 140'), but later turned into a compromise which led to the development of an advanced 120 mm gun, the L/55, based on the same internal geometry as the L/44 and installed in the same breech and mount. The L/55 is longer, generating increased muzzle velocity for rounds fired through it. As the L/55 retains the same barrel geometry, it can fire the same ammunition as the L/44.
The L/55 gun was retrofitted into German and Dutch Leopard 2s, and chosen as the main gun of the Spanish Leopard 2E and the Greek Leopard 2HEL. It was tested on the British Challenger 2 as a potential replacement for its rifled L30 120 mm cannon, ultimately leading to the Challenger 3.
A variety of ammunition has been developed for use by tanks with guns based on Rheinmetall's original L/44 design. This includes a series of kinetic energy penetrators, such as the American M829 series, and high-explosive anti-tank warheads. Recent ammunition includes a range of anti-personnel rounds and demolition munitions. The LAHAT, developed in Israel, is a gun-launched anti-tank guided missile which has received interest from Germany and other Leopard 2 users. It is designed to defeat both land armour and combat helicopters. The Israelis also introduced a new anti-personnel munition which limits collateral damage by controlling the fragmentation of the projectile.
Background
The development of the 120 mm L/44 gun started in 1965, as the Bundeswehr felt a more powerful gun was needed for its new tanks.Rheinmetall, , accessed 9 January 2009Jane's Armour & Artillery (subscription), Rheinmetall L44 smoothbore gun (Germany) , accessed 6 November 2008, claims development began in 1964. The first instance of a larger Soviet tank gun was witnessed on the chassis of a modified T-55 in 1961.Norman, p. 14 In 1965, the Soviet Union's T-62 made its first public appearance, armed with a smoothbore tank gun.Zaloga (1979), p. 20 The Soviet decision to increase the power of its tank's main armament had come when, in the early 1960s, an Iranian tank commander defected over the Soviet border in a brand-new M60 Patton tank, which was armed with the M68 gun, the US version of the British Royal Ordnance L7.Zaloga (2004), p. 5 Despite the introduction of the T-62, in 1969 their T-64 tank was rearmed with a new tank gun, while in 1972 Nizhny Tagil began production of the T-72 tank, also armed with the gun.Zaloga (2004), p. 7 At the fighting at Sultan Yakoub, during the 1982 Lebanon War, the Israeli government claimed to have destroyed nine Syrian T-72s with the Merkava main battle tank, armed with an Israeli version of the American M68 tank gun.Warford (2006), pp. 23–24 Whether true or not, the Soviets test-fired a number of Israeli M111 Hetz armor-piercing discarding sabot rounds at Kubinka, finding the round was able to perforate the sloped front section plate but not the turret armour of the T-72 tank.Warford (2006), p. 24 In response, the Soviets developed the T-72M1.Warford (2006), p. 25 This led Israel to opt for a 120 mm tank gun during the development process of the Merkava III main battle tank.Katz (1997), 38 This case is similar to the American decision to replace the M68 tank gun with Rheinmetall's 120 mm gun in 1976; the introduction of the T-64A had raised the question within the armour community of whether the new ammunition for the existing gun calibre could effectively defeat the new Soviet tank.Green (2005), 32–33
In 1963, Germany and the United States had already embarked on a joint tank program, known as the MBT-70. The new tank carried a crew of three, with the driver in the turret, an automatic loader for the main gun, a autocannon as secondary armament, an active hydropneumatic suspension and spaced armour on the glacis plate and front turret.Hilmes (2001), p. 17 The new tank concept also had improved armament, a missile-launching main gun, designed to fire the MGM-51 Shillelagh anti-tank missile.Zaloga (1982), p. 19 However, the German Army was interested in a tank gun which could fire conventional ammunition. Although there were attempts to modify the tank gun to do so, the process proved extremely difficult, and the Germans began development of the future Rheinmetall 120 mm gun instead.McNaugher (1981), p. vi
In 1967, the German ministry of defence decided to re-open a Leopard 1 improvement program, known as the Vergoldeter Leopard ('Gilded Leopard'), later renamed the Keiler ('Wild Boar'). Krauss-Maffei was chosen as the contractor, and two prototypes were developed in 1969 and 1970.Jerchel (1998), p. 5 This program grew into the Leopard 2; the first prototype of the new tank was delivered in 1972, equipped with a smoothbore main gun. Between 1972 and 1975, a total of 17 prototypes were developed.Hilmes (2001), p. 18 The new 120 mm gun's ten-year development effort ended in 1974. Ten of the seventeen turrets built were equipped with 105 mm smoothbore guns, and the other seven were equipped with larger, 120 mm, guns.Jerchel (1998), p. 6 Another program aimed to mount the missile-gun was also begun in an attempt to save components from the MBT-70, but in 1971 the program was ended for economic reasons.Jerchel (1998), pp. 6–7 Instead, the Germans opted for Rheinmetall's 120 mm L/44 smoothbore tank gun.Jerchel (1998), p. 7
Design features
Rheinmetall's L/44 tank gun has a calibre of 120 mm, a length of 44 calibres (), and a chamber volume of 10.2 liters (622.44 in3).The development work 2016-2020, edrmagazine.eu, 05-03-2021Rheinmetall Defense, L44 Tank Gun, accessed 9 November 2008; barrel length can be found by multiplying the caliber length by the caliber diameter. The gun's barrel weighs ,Maxwell (2002), p. 82 and on the M1 Abrams the gun mount weighs ,Green (2005), p. 61 while the new barrel (L/55) is 55 calibres long, longer. The bore evacuator and the gun's thermal sleeve, designed to regulate the temperature of the barrel, are made of glass-reinforced plastic, while the barrel has a chrome lining to increase barrel life. Originally the gun had an EFC barrel life of ~1,500 rounds, but with recent advances in propellant technology, the average life has increased even further. The gun's recoil mechanism is composed of two hydraulic retarders and a hydropneumatic assembly.
Variants
Rh-120 L/44 120mm Production of the German Leopard 2 and the new 120 mm tank gun began in 1979, fulfilling an order for the German Army.Jerchel (1998), p. 11 The L/44 Extreme Service Condition Pressure (ESCP) is , the Permissible Maximum Pressure (PMP) , and the Design Pressure from .New 120 mm gun and ammunition; a 20% performance increase in the coming years, edrmagazine.eu, 05-03-2021 Although the American M1 Abrams was originally armed with the M68A1 105 mm gun (a version of the L7),Green (1992), p. 56 the United States Army had planned to fit the tank with a larger main gun at a later date,Chait (2005), p. 12 and the tank's turret had been designed to accommodate a larger 120 mm gun. The larger gun was integrated into the M1A1 Abrams, with the first vehicle coming off the production line in 1985Green (2005), pp. 24–29 The gun, known as the M256, was based on the L/44 tank gun, although manufactured at Watervliet Arsenal. Tanks armed with versions of Rheinmetall's gun produced under licence include Japan's Type 90Bolté (1997), p. 25 and South Korea's K1A1.Clemens (1999), p. 15; based on the United States' M256 gun. The M256 based on the L/44 when firing M829A1 Armor Piercing, Fin Stabilized, Discarding Sabot - Tracer (APFSDS-T) ammunition can attain a Peak Chamber Pressure of at and at .M256 120mm Smoothbore Gun
Rh-120 L/55 120mm
The appearance of new Soviet tanks such as the T-80B during the late 1970s and early 1980s led to the development of new technologies and weapons to counter the threat posed to Western armour.Jerchel (1998), p. 24 The T-80B had increased firepowerBaryatinskiy (2006), pp. 23–25 and new composite ceramic armour.Baryatinskiy (2006), p. 14 The T-72 also went through a modernization program in an attempt to bring it up to the standards of the T-80B. In 1985 the new T-72B version entered production, with a new laminate armour protection system; its turret armour, designed mainly to defeat anti-tank missiles, surpassed the T-80B's in protection.Zaloga (1993), p. 10
The German government began developing the Leopard 3, although this was canceled after the fall of the Soviet Union.Jerchel (1998), pp. 33–34 On 29 October 1991, the governments of Switzerland, the Netherlands and Germany agreed to cooperate in the development of a modernization program for the Leopard 2. Part of this program included the introduction of a longer 120 mm tank gun,Jerchel (1998), p. 34 a cheaper alternative to a new tank gun,Hilmes (2004), p. 76 increasing the maximum range of the gun by an estimated . Although the gun is longer, allowing for longer and a higher peak pressure from the propellant, the geometry remains the same, allowing the gun to fire the same ammunition as that fired from the shorter version.Jane's Armour & Artillery Upgrades (subscription), Rheinmetall L55 smoothbore gun (Germany), accessed 2008 The longer barrel allows ammunition to attain higher velocities; for example, with new kinetic energy penetrators ammunition can reach velocities of around .Rheinmetall Defence, L55 Tank Gun , accessed 2008 The new barrel weighs .
The longer tank gun has been retrofitted into the Leopard 2, creating a model known as the Leopard 2A6. The Spanish Leopard 2E, the Greek Leopard 2HEL, and derivatives of the Leopard 2A6, use 55 calibre-long tank guns.Candil (2007), p. 66
Rh-120 L/55 A1 120mm The Rh-120-55 A1 is similar to earlier Rh-120 L/55 model. Compared to the L/44 and L/55, the L/55 A1 Extreme Service Condition Pressure (ESCP) is raised from , the Permissible Maximum Pressure (PMP) from , and the Design Pressure from . It is also known as the L/55A1 and entered service in 2018.
Rh-130 L/52 130mm
Russia introduced a new generation of armoured vehicles like the T-14 Armata tank in 2015. In response, Rheinmetall started the development of a larger 130 mm tank gun, financed entirely using internal funding. The first technical demonstrator (TD) was completed in May 2016 and presented at Eurosatory 2016 in June 2016.What future for tank guns? The Rheinmetall view, edrmagazine.eu, 05-03-2021