Rheinmetall 120 mm gun The Rheinmetall 120 mm gun is a smoothbore tank gun designed and produced by the West German Rheinmetall - DeTec AG company , developed in response to Soviet advances in armor technology and development of new armored threats . Production began in 1974 , with the first version of the gun , known as the L / 44 as it was 44 calibers long , used on the German Leopard 2 tank and soon produced under license for the American M1A1 Abrams and other tanks . The American version , the M256 , uses a coil spring recoil system instead of a hydraulic system . The gun has also been exported to South Korea and Japan for their indigenous tank designs , as well as other nations that have procured the Leopard 2 and the M1 Abrams . The gun has a length of , and the gun system weighs approximately . By 1990 the L / 44 was not considered powerful enough to deal with the future Soviet armour , which stimulated an effort by Rheinmetall to develop a better main armament . This first revolved around 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 , giving an increased muzzle velocity to ammunition fired through it . As the L / 55 retains the same barrel geometry , it can fire the same ammunition as the L / 44 . This gun was retrofitted into German and Dutch Leopard 2s , and chosen as the main gun of the Spanish Leopard 2E , the Greek Leopard 2HEL , and South Korean K2 Black Panther battle tank . It has been tested on the British Challenger 2 as a potential replacement for its current weapon , the rifled L30 120 mm cannon . This test however has been stopped due to the characteristics of the Challenger 2 . 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 chemical energy anti - tank warheads . Recent ammunition includes a wide range of new anti - personnel rounds and demolition munitions , giving tanks armed with the L / 44 and its derivatives greater versatility on the modern battlefield . The LAHAT , developed in Israel , is a gun - launched missile which has received interest from Germany and other Leopard 2 users , and 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 . Worried about the inability of the L7 tank gun then in use across NATO forces to penetrate new Soviet armor , Rheinmetall began development of a new tank gun in 1965 . The first instance of a larger Soviet tank gun was witnessed on the chassis of a modified T - 55 in 1961 . In 1965 , the Soviet Union ' s T - 62 made its first public appearance , armed with a smoothbore tank gun . 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 British Royal Ordnance L7 . 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 . For example , 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 production version of the American M68 tank gun ( which in turn was based on the British L7 ) . Whether or not true , 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 T - 72 ' s sloped front section plate but not its turret armor . In response , the Soviets developed the T - 72M1 . This led Israel to opt for a 120 mm tank gun during the development process of the Merkava III main battle tank . 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 armor community whether the new ammunition for the existing gun caliber could effectively deal with the new Soviet tank . 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 three - man crew , 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 the front turret . The new tank concept also had improved armament , a missile - launching main gun , designed to fire the MGM - 51 Shillelagh anti - tank missile . 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 . In 1967 the German Ministry of Defense 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 . 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 . The new 120 mm gun ' s ten - year development effort , which had begun in 1964 , ended in 1974 . Ten of the 17 turrets built were equipped with the 105 mm smoothbore gun , and the other seven were equipped with the larger 120 mm gun . Another program aimed to mount the missile - gun was also developed in an attempt to save components from the MBT - 70 , but in 1971 the program was ended for economic reasons . Instead , the Germans opted for Rheinmetall ' s 120 mm L / 44 smoothbore tank gun . Design features . Rheinmetall ' s L / 44 tank gun has a caliber of 120 mm , and a length of 44 calibers ( ) . The gun ' s barrel weighs , and on the M1 Abrams the gun mount weighs , while the new barrel ( L / 55 ) is 55 calibers 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 a barrel life of between 400 and 500 rounds , but with recent advances in propellant technology the average life decreased to 260 rounds . In some cases , barrels have had to be replaced after firing only 50 projectiles . The gun ' s recoil mechanism is composed of two hydraulic retarders and a hydropneumatic assembly . Rheinmetall L44 120mm . Production of the German Leopard 2 and the new 120 mm tank gun began in 1979 , fulfilling an order for the German Army . Although the American M1 Abrams was originally armed with the M68A1 105 mm gun ( a version of the L7 ) , the United States Army had planned to fit the tank with a larger main gun at a later date , 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 1985 The gun , known as the M256 , was based on the L / 44 tank gun , although manufactured at Watervliet Arsenal and modified to increase the resistance of the barrels to fracture and fatigue . Tanks armed with versions of Rheinmetall ' s gun produced under licence include Japan ' s Type 90 and South Korea ' s K1A1 . The gun had made a huge turn in technological history . Rheinmetall L55 120mm . The appearance of new Soviet tanks such as the T - 80B during the late 1970s and early 1980s demanded the development of new technologies and weapons to counter the threat posed to Western armor . The T - 80B had increased firepower and a new composite ceramic armor . 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 armor protection system ; its turret armor , designed primarily to defeat anti - tank missiles , surpassed the T - 80B ' s in protection . The German government began the development of the Leopard 3 , although this was canceled after the fall of the Soviet Union . On 1991 , the governments of Switzerland , 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 , a cheaper alternative to a brand new tank gun , increasing the maximum range of the gun by an estimated . Although the gun is longer , allowing for 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 . The longer barrel allows ammunition to attain higher velocities ; for example , with new kinetic energy penetrators ammunition can reach velocities of around . The new barrel weighs . The longer tank gun has been retrofitted into the Leopard 2 , creating a model known as the Leopard 2A6 . Both the Spanish Leopard 2E and the Greek Leopard 2HEL , as derivatives of the Leopard 2A6 , use the 55 caliber - long tank gun . Ammunition . A variety of rounds have been developed for Rheinmetall ' s tank gun . For example , a long line of armor - piercing discarding sabots was developed by Rheinmetall . Originally , the Leopard 2 was outfitted with the DM23 kinetic energy penetrator , based on the Israeli M111 " Hetz " . The DM23 was eventually replaced by the DM33 , which was also adopted by Japan , Italy , Netherlands and Switzerland . The DM33 has a three - part aluminum sabot and a two - part tungsten penetrator , and is said to be able to penetrate of steel armor at a range of . The DM43 is a further development of this round , co - developed between Germany and France . The introduction of the longer barrel came hand in hand with the introduction of a new kinetic energy penetrator , the DM53 . Weighing in at 8 . 35 kilograms with a 38 : 1 length to diameter ratio and with a muzzle velocity of , the projectile has an effective engagement range of up to . A further development , called the DM63 , improved upon the round by introducing a new temperature - independent propellant , which allows the propellant to have a constant pattern of expansion between ambient temperatures inside the gun barrel from to . The new propellant powders , known as surface - coated double - base ( SCDB ) propellants , allow the DM63 to be used in many climates with consistent results . The new ammunition has been accepted into service with the Dutch and Swiss , as well as German , armies . The United States developed its own kinetic energy round using a depleted uranium penetrator known as the M829 , followed by improved versions . An immediate improvement , known as the M829A1 , was called the " Silver Bullet " after good combat performance during the Gulf War against Iraqi T - 55s , T - 62 s and T - 72s . The M829 series centers around the depleted uranium penetrator , designed to penetrate enemy armor through kinetic energy and to shatter inside the turret , doing much damage within the tank . In 1998 the United States military introduced the M829A2 , which has an improved depleted uranium penetrator and composite sabot petals . In 2002 , production of the M829A3 began , which is said to be able to defeat the latest versions of Russian explosive reactive armor . Both Germany and the United States have developed several other rounds . These include the German DM12 multi - purpose anti - tank projectile ( MPAT ) , based on the technology in a high explosive anti - tank ( HEAT ) warhead . However , it has been found that the DM12 ' s armor - killing abilities are limited by the lack of blast and fragmentation effects , and that the round is less valuable against lightly armored targets . The United States also has a MPAT type projectile , known as the M830 . This was later developed into the M830A1 , which allows the M1 Abrams to use the round against helicopters . The M1 Abrams can use the M1028 canister round , which is an antipersonnel munition , packed with over 1 , 000 tungsten balls . The United States Armed Forces accepted a new demolition round , called the M908 Obstacle Defeating Round , based on the M830A1 MPAT , but with the proximity fuse replaced by a hardened nose cap . The cap allows the round to impact and embed itself in concrete , then exploding inside the target and causing more damage . The Israeli Army introduced a new round known as the Laser Homing Anti - Tank ( LAHAT ) projectile . Using a semi - active laser homing guidance method , the LAHAT can be guided by the tank ' s crew or by teams on the ground , while the missile ' s trajectory can be selected to either attack from the top ( to defeat enemy armor ) or direct attack ( to engage enemy helicopters ) . Furthermore , the missile can be fired by both and 120 mm tank guns . The LAHAT has been offered as an option for the Leopard 2 , and has been marketed by both Israel Military Industries and Rheinmetall to Leopard 2 users . Israeli Merkavas make use of a round known as the APAM , which is an anti - personnel munition designed to release fragmentation at controlled intervals to limit the extent of damage . Fragments are shaped to have enough kinetic energy to penetrate body armor . Poland has introduced a series of projectiles for Rheinmetall ' s tank gun , including an armor - piercing penetrator target practice round ( APFSDS - T - TP ) , a high - explosive round , and a high - explosive target practice ( HE - TP ) projectile . The ammunition is manufactured by " Zakłady Produkcji Specjalnej Sp . " Operators . Due to tank sales , Rheinmetall ' s L / 44 tank gun has been manufactured for other nations . For example , the Leopard 2 armed with the 44 caliber long gun , has been sold to the Netherlands , Switzerland , Sweden , Spain , Austria , Denmark , and other countries . Egypt had manufactured 700 – 800 M1A1 Abrams by 2005 , and in 2008 requested permission to build another 125 tanks ; their M256 main guns ( the US version of the L / 44 ) were manufactured by Watervliet Arsenal . The M1A1 has also been exported to Australia , while the M1A2 Abrams has been exported to Saudi Arabia and Kuwait . The Leopard 2A6 and its longer L / 55 main gun have been exported for use by the Canadian Army , and the Netherlands upgraded part of its original fleet of Leopard 2s with the more powerful armament . The British Army has tested Rheinmetall ' s longer gun , possibly looking to replace the current L30 A1 120 mm L / 55 rifled main gun on the Challenger 2 . Two Challenger 2s were modified to undergo firing trials . World Industries Ace Corporation is also producing the L / 55 under license for the K2 Black Panther .