M60 tank

The United States entered a period of frenzied activity during the crisis atmosphere of the Korean War, when America seemed to lag behind the Soviet Union in terms of tank quality and quantity.[18] Testing and development cycles occurred simultaneously with production to ensure speedy delivery of new tanks. Such rapid production caused problems but the importance given to rapidly equipping combat units with new tanks precluded detailed testing and evaluation prior to quantity production.[18]

The M47 Patton entered production in 1951 and was used by the United States Army and Marine Corps but ongoing technical and production problems kept it from serving in the Korean War. The M48 Patton tank entered US service in 1952 but its early designs were deemed unsatisfactory by Army Field Forces (AFF). The improvements to the M48 focused on improving the 90mm main gun and fire control systems while simultaneously exploring the development of silicas glass composite armor and autoloader systems. The tank continued further development through 1955 in conjunction with its simultaneous mass production. The course of its development during the mid 1950s was the source of widespread debate among Congressional Budget Oversight committees.

The T95 program, which began in 1955 was intended to supersede the M48. It featured a host of innovative and experimental components such as its 90 mm smoothbore T208 cannon rigidly affixed to its turret, experimental X-shaped engine design using a vapour-cycle power plant fueled by hydrocarbons, composite armor and infrared rangefinder. The burden of developing them, however, slowed the overall program to a crawl. During the Hungarian Revolution of 1956, a Soviet T-54A medium tank was driven onto the grounds of the UK's embassy in Budapest by the Hungarians in November.[19] After a brief examination of this tank's armor by a British military attaché it was concluded that the 20-pounder (84mm L/66.7) was apparently incapable of consistently defeating its frontal armor with HEAT or APC ammunition. Its 100 mm gun was a significant advancement over the weapon of the T-44. Also there were rumors of an even larger 115 mm gun in the works. These events spurred the United Kingdom to begin upgrading existing tanks with a 105mm high-velocity rifled gun in 1957, the Royal Ordnance L7 to keep the Centurion viable against this new Soviet tank design. The United States responded by starting development of the XM60 tank in September 1957.[20] This new tank design incorporated many Army Combat Vehicle (ARCOVE) committee improvements to the M48A2, chiefly the use of diesel engines to increase its operational range and the use of a more powerful main gun.

The main gun was chosen after a comparative firing test of six different guns carried out on the Aberdeen Proving Grounds in 1958. The factors evaluated were accuracy, lethality of a hit, rate of fire and penetration performance.[21]

An M48A2C was fit with the 90 mm M41 and tested with the new T300E53 HEAT round. A smoothbore version of the 90 mm, the T208E9, was mounted on the T95E1 tank and tested the T320E62 APDS round. An American version of the British 105 mm gun the Royal Ordnance L7, under the US designation 105 mm T254E1, was mounted on the T95E2 and tested with British APDS ammunition. Finally, two versions of the 120 mm gun from the M103 were trialed, the existing M58 model and a lightened variant known as T123E6 which was mounted on the T95E4.[22]

The T123E6 was preferred by the Ordnance Department because its ammunition, the same as that for the M58 gun, was already at an advanced state of development.[23] However the ammunition was in two parts, shell and propellant bag, which required significant time to load. In the M103 this was addressed by adding a second loader, but a medium tank would not have the internal space needed for another crewmember and the firing rate would suffer as a result. In testing it demonstrated a maximum rate of 4 rounds per minute vs. the T254's 7 rpm.[21]

Based on these tests, the 105 mm T254E1 was selected, modified to the T254E2 and standardized as the "Cannon, 105mm Gun, M68". It used a vertical sliding breechblock instead of the T254E1's horizontal breechblock. Until American-made barrels could be obtained with comparable accuracy, British X15/L52 barrels were to be used.[22] US built XM24/L52 barrels (length 218.5 inches)[24] fitted with an eccentric bore evacuator were used for the M60-series starting in June 1959 but retained interchangeability with the British X15/L52 barrel.[25] All of the US guns and XM24 barrels were produced at the Watervliet Arsenal, NY and the gun mounts (M116 for the M60 and M140 for the M60A1/A3) manufactured at the Rock Island Arsenal, IL.[26] Because the evacuator was positioned lower on the gun's barrel US M68 guns were fitted with an eccentric bore evacuator instead of a concentric model in order to provide more clearance over the rear deck.[27] The original variant of the M60 tank was equipped with the M68 gun using the M116 mount.[28] The M60A1 and A3 variants of the M60 tank series[29] and earliest pre-production XM1 prototypes of the M1 Abrams tanks[30] are armed with the M68E1 variant of the gun. The M68E1 gun shares the same firing characteristics as the M68. It featured several design improvements including an updated gun hydraulic configuration, a stabilization upgrade for the gun, a gun elevation kill switch for the loader, improved ballistic drive and other component refinements.[29] Additionally, many M48A3s armed with a 90mm gun that were in NG-CONUS service with the Army National Guard were retrofitted with the M68 gun during the mid 1970s[31] and redesignated as the M48A5.[32] This was done to maintain training levels of Guard units as well as using a commonality in ammunition amongst tanks.

The gun is capable of using a wide range of ammunition including APDS-T (M932 and M728), APFSDS-T (M774 and M735), APFSDS-DU (M744A1 and M833), HEAT-FS (M456), APDS dummy and target practice rounds, HEP/HESH (M393), white phosphorus and canister rounds.[33] Barrels with thermal sleeves were used starting in 1973.[34]

Composite applique armor panels made with fused silica glass was intended to be fitted to the hull. This led to a redesign of the front of the hull into the shape of a flat wedge, instead of the M48's elliptical front, as it simplified the installation of this armor. It was also envisioned that the T95E6 turret was to be constructed solely with this special armor.[35] The US Army Ordnance Tank Automotive Command (OTAC) and the Carnegie Institute of Technology began development of the armor in November 1952 at Fort Belvoir VA as Project TT2-782/51 using examples of the T95 tank to conduct the ballistics testing.[36] This composite armor provides protection against HEAT, HEP/HESH and HE rounds. However, field repaired panel castings suffered a loss of kinetic energy protection.[37] Limitations in manufacturing capacity and the added cost led to this armor being dropped by November 1958[36] and all M60-series tanks were protected with conventional steel armor.[38] The M60-series was the last US main battle tank to utilize homogeneous steel armor for protection. It was also the last to feature an escape hatch under the hull. The escape hatch was provided for the driver, whose top-side hatch could easily be blocked by the main gun.[39]

There were two versions of hulls used for the M60-series. The M60 hull had a straight slope and beak compared to the earlier M48's rounded one. The hull bottom had a strong boat-like appearance with a pronounced recess between the upper tracks and external suspension arms and one shock absorber on the first roadwheel pair. The armor was improved, at 6 inches (155 mm) on the front glacis and mantle of solid rolled homogeneous armor, while it was 4.3 inches (110 mm) on the M48. The first prototype hulls did not have shock absorbers and were briefly named M68 in late 1958 before the Ordnance Department renamed it the M60 in March 1959.[40] This hull version was used only on the original M60 variant and early M728s and M60AVLBs. This hull model was in production from 1959 to 1962.

The M60A1 hull has basically the same visual characteristics, the noticeable difference was the addition of a second shock absorber at the second roadwheel pair and was also accompanied by a slight relocation of the first return roller. These modifications were needed due to the increased weight of the M60A1 turret as well as the additional hull armor. This hull model was used on the M60A1, M60A2 and M60A3 models of the M60-series as well as the M728A1 and M60A1 AVLB. It was in production from 1962 to 1983.[41]

The M60-series went through a progressive turret design scheme during its production life with four different turrets being manufactured for the M60-series. The T95E5 turret used on the M60 was hemispherically shaped and bore a strong resemblance to the M48 Patton. The M60A1 was the first version to employ the newly designed T95E7 turret with a redesigned bustle increasing the number of rounds for the main gun to 63. The M60A2 featured a specially designed turret for the M162 gun/missile launcher that greatly reduced the frontal arc in comparison to the M60A1's T95E7 turret. The M60A3's turret was similar to the A1's but with increased armor protection for the frontal arc and mantlet in an effort to provide additional protection of the turret's hydraulics system.

A redesigned full vision cupola was envisioned for the commander's station. It had 7 tiltable vision blocks arranged to give the commander a 360 degree field of view with overlapping vision between adjacent vision blocks. The front vision block could be replaced with a dual power M34 7x50 binocular day sight or an M19E1 IR periscope. A special feature was that the cupola body could be raised up to 3 1/2 inches providing the commander a direct field of vision while remaining under armor protection. Access was through a hatch cover on the roof and a .50 caliber M2HB machine gun was pedestal mounted on the forward part of the cupola. It could be aimed and fired with the cupola closed. Also there was an 11 inch long hydraulically operated port on the left side allowing spent cartridge cases to be ejected.[38] After creating a full-sized mock up of this design using the T95E6 turret, it was dropped in favor of a design based on the M1 cupola of the M48A2's turret. This T9 cupola provided the commander with more headroom than the T6 cupola of the T95 tank, carrying a new short receiver M85/T175 .50 caliber machine gun[38] and it was standardized as the Cupola, Tank Commander's Caliber .50 Machine Gun, M19.[13] The first M19 cupola (a modified T9) was ready on 27 October 1958. It has an M28C sight for the machine gun in the forward part of the cupola and eight vision blocks. The front vision block can be replaced by a M19E1 infrared periscope or an M36E1 passive periscope for night observation.[42] Initial production of the cupola was problematic. The first 300 M60s produced were armed with a .50cal M2HB machine gun in a pedestal mount welded to the left side of the commander's cupola owing to production problems with the new M85 machine gun. Of these tanks, the first 45 manufactured were made without the cupola itself, also due to production problems.[43] All of these early M60s eventually had the M19 cupola and M85 machine gun installed.

Compared to a conventional pintle mount, the remote-controlled M85 machine gun was relatively ineffective in the anti-aircraft role for which it was designed. Removing the cupola lowered the vehicle's relatively high silhouette. The cupola's hatch also opened toward the rear of the vehicle and was dangerous to close if under small-arms fire owing to a lock-open mechanism that required the user to apply leverage to unlock it prior to closing. The commander was able to observe the battlefield using the x4 binocular M34D daylight vision block or the M19E1 IR or M36 Passive periscopes while remaining under armor protection with a 360 degree traverse independent of the turret,[44] was stabilized in azimuth and elevation[45] and carried 600 rounds of ammunition.[46] All M60s in US service retained the M19 cupola until the tank was phased out of service. The few M60A3s in Army service as training vehicles had their commander's cupola removed as it was deemed unnecessary for training and to better mimic the profile of Soviet tanks. Some M48A5s were retrofitted with the M19 cupola to maintain training levels of National Guard units.

The concept of the medium tank gradually evolved into the Main Battle Tank (MBT) in the 1960s. The MBT was to combine the firepower and protection sufficient for the assault role with the mobility to perform as a medium tank.[47] The main battle tank thus took on the role the British had once called the "universal tank", exemplified by the British Centurion, filling almost all battlefield roles. Typical main battle tanks were as well armed as any other vehicle on the battlefield, highly mobile, and well armored. Yet they were cheap enough to be built in large numbers. The first generation consists of the medium tanks designed and produced directly after World War II that were later redefined as main battle tanks. These were exemplified by the M47 and M48 Pattons armed with a 90mm main gun already in widespread US service. The original variant of the M60 series also fulfilled the definition of a late first generation MBT sometimes being referred to as an intermediate second generation design. The Soviet T-54 and T-55 as well as the original configuration of the T-62A tank designs are also regarded as first generation MBTs. The second generation had enhanced night-fighting capabilities and in most cases NBC protection. Most western tanks of this generation were armed with the 105 mm Royal Ordnance L7 tank gun or derivatives of it. Notable are the British Chieftain and German Leopard 1. The United States fully committed to the main battle tank doctrine in 1963 when the Marine Corps deactivated its last M103 Heavy Tank battalion.[48] The first American nomenclature-designated second generation MBT was the M60A1 version of the M60 series. The term MBT is used in strategic doctrine and the composition of force as determined by the United States Army. The M60 series tanks fulfilled the MBT role on a strategic and tactical level. It was never referred to as such in any official training or technical manuals. The first Soviet second generation main battle tank designs were the T-64 and T-72.[49]

By May 1957 it became clear that the T95 Medium Tank would not have a significant advantage over the M48A2. The X-shaped motor and electro-optical rangefinder were both discarded due to performance, and the accuracy of the smoothbore gun and its HVAP-DS ammunition continued to be unsatisfactory. The T95E6 turret was to be made with the advanced silicas armor but was never constructed. All this led to the closure of the T95 project on July 7, 1960. But the T95E7 turret design using conventional hardened steel armor was carried forward, becoming the M60A1's turret.[47] The course of the M48 Patton's tank production was the source of widespread Congressional debate. The Bureau of the Budget believed that the Army was not progressing with sufficient speed in its tank modernization program and recommended the immediate replacement of the M48A2. Correctly predicting that Congress would not approve the procurement of the M48A2 after the fiscal year 1959, the Deputy Chief of Staff, Logistics (DCSLOG) proposed a tank based on the M48A2 featuring improved firepower and the AVDS-1790 engine. Since the main gun had not yet been specified, four XM60 weapons systems were submitted in September 1957.

Concept design #1 of the XM60 mounting the T123E6 main gun and British styled gun barrel, the newly designed full-vision cupola using the T95E6 turret as preferred by the Ordnance Department.

The first concept was armed with the 120mm gun T123E6 in the long nosed T95E6 turret. This was the design preferred by the Ordnance Department. It was fitted with a mock-up of the new designed full-vision commander's cupola. A full sized prototype of this turret was constructed before this concept was dropped, mainly due to its slow rate of fire. The second carried the 105mm rifled T254E2 main gun in the T95E5 type turret and the T9 cupola style of the M48A2. The T254 guns used British X15/L52 barrels with a concentric bore evacuator on the barrel.[50] The Army Ordnance Technical Committee chose this design for production in August 1958. The third concept was to mount the 90mm T208 smooth-bore main gun and the T95E6 turret with the T6 cupola of the T95 tank. It never progressed beyond design drawings. The fourth used the T95E1 turret and the T208 main gun. A mock-up was built using the new vision cupola. All of these conceptual designs were referred to as the XM60. A contract was awarded to Chrysler Engineering in September 1958 for the advanced production engineering (APE) of the XM60 concept #2.[51] The T95 hull was considered however its one-piece front casting was too difficult and expensive to produce in quantity. Some existing T95 hulls were re-fitted with the AVDS-1790 engine and used from 1960 to 1964 to develop the T118E1 prototyping of the M728 Combat Engineer Vehicle.[52] Instead the decision was made to use modified M48A2 hulls. The hulls had 3 return rollers and 6 steel roadwheel pairs per side with no shock absorbers, using only bumper springs on the first and sixth roadwheel arms, along with a widened turret well and ring, and a flat wedge-shaped glacis. The T254E2 gun was chosen to be the main weapon of the tank in August 1958 being standardized as the M68 105mm gun. After a briefing on 11 December 1958, General Maxwell Taylor ordered the XM60 into production because of the improvements it offered in firepower, protection, and cruising range.[51] Since the tank had not yet received its official designation these prototype hulls were briefly referred to as the M68 in December 1958 until they were officially named the M60 in March 1959.[40] Fulfilling this requirement was an interim tank design that resulted in the M60-series,[25] which largely resembles the M48A2 Patton it was based on, but has significant differences. The visual similarity of these designs as well as their overlapping period of service has caused some sources to incorrectly label the M60 as a Patton tank.

M60 production pilot number 1 after completion by Chrysler on 2 July 1959. Note the use of a pedestal mounted M2HB machine gun on the cupola. The turret is traversed to the rear of the tank.

The OTCM (Ordnance Technical Committee Minutes) #37002 officially standardized the type as the Tank, Combat, Full Tracked: 105-mm Gun, M60 on 16 March 1959.[53] The production contract was approved April 1959 with the low rate initial production starting in June at the Chrysler Corporation Delaware Defense Plant in Newark Delaware.[25] Production pilot 1 was completed at Chrysler Defense Engineering on 2 July and sent to the Aberdeen Proving Ground with an initial production total of 45 tanks in July 1959. Production pilot 2 was finished on 4 August and used to develop technical publications and an additional 47 tanks produced to complete the first low rate production buy. In August 1959, an engineering bid package was awarded for the second low rate production buy of M60s to be built at the Delaware Plant. Production pilot 3 was completed 2 September and went to the Detroit Arsenal Test Center for maintenance evaluations, it was then sent to Fort Knox for user trials. The fourth pilot was completed on 26 October and was used as the master hull to verify production standards at the Detroit Tank Plant with a low-rate initial production total of 180 M60s built in 1959.[42] Subsequent production, starting with the October 1960 batch were built at the Detroit Arsenal Tank Plant, in Warren Michigan. It reached operational capability with fielding to Army units in Europe beginning in December 1960.[16]

Features

The original variant of the M60 series ultimately was produced as a quick fix engineering (QFE) upgrade of the M48 due to the Soviet Union's tank advancements of the late 1950s and the delays from developing the silicas armor and an improved turret design. The M60 mounted a 105 mm M68 main gun with the bore evacuator mounted towards the middle of the tube carrying 57 rounds in the clamshell shaped turret style of the M48. Nine rounds were stowed in the left side of the turret bustle behind the loader.[54] The remaining rounds were stored inside safe containers on the hull floor.[40] A new short receiver coaxial machine gun was designed for the M60 tank. This was the 7.62mm M73/T197E2 which replaced the .30 caliber M37 used on the M48A2. It had 2,000 rounds of ammunition.[46] They had a reputation for jamming. After working to correct this, they were redesignated as the M73A1 in 1970.

M60 with AN/VSS-1(V)1 IR searchlight on display at Mississippi Armed Forces Museum, Camp Shelby, Mississippi

The electronics package on the M60 was essentially the same as used on the M48A2C including an improved turret control system and an all-metric measurement M16 Fire Control System (FCS), The M16 FCS consists of a new M10 ballistic drive and mechanical M16E1 gun data computer which integrated barrel temperature data[55] with an M17 coincidence range finder.[45] The rangefinder is a double image coincidence image instrument used as the ranging device of the gunner's primary direct sighting and fire control system. The gunner is provided with an M31E1 day periscope with a magnification of x8 and an M105D day telescopic sight with a magnification of x8 and a field of view of 7.5 degrees.[42] Range information from the rangefinder is fed into the ballistic computer through a shaft. The ballistic computer is a mechanically driven unit that permits ammunition selection, range correction, and superelevation correction by the gunner. The ballistic drive receives the range input and, through the use of cams and gears, provides superelevation information to the superelevation actuator. The superelevation actuator adds sufficient hydraulic fluid to the elevating mechanism to correctly position the gun.[55]

In late 1962 a kit was fielded that allowed the use of the AN/VSS-1(V)1 IR searchlight. The searchlight has both infrared and visible light capabilities and was positioned over the gun. Along with an M32 IR periscope for the gunner, M19 IR periscope and M18 IR binoculars for the commander provided first generation night vision capability to the M60 and M60A1 tanks. This kit was also compatible with the M48A3/A5.[56]

The hull bottom had a strong boat-like appearance with a pronounced recess between the upper tracks and external suspension arms with cast aluminum roadwheels and return rollers along with a single shock absorber on the first roadwheel pair. Cast aluminum road wheels were used to save weight. The armor was improved, at 6 inches (155 mm) on the front glacis and mantle of solid rolled homogeneous armor, while it was 4.3 inches (110 mm) on the M48. Power was provided by the AVDS-1790-2A engine, CD-850-5 cross drive transmission and the T97E2 track assembly as used on the M48A3.[57] The drive sprocket is located at the rear of the hull. The vehicle also provides full NBC protection for the crew using the M13A1 protection system creating a positive atmospheric pressure in the crew compartment. The positive pressure keeps contaminated air out and forces the smoke produced from firing the main or coax guns out of the vehicle. Access between the driver's compartment and the turret fighting compartment was also restricted, requiring that the turret be traversed to the rear.

The M60 was deployed to West Germany to counter the threat presented from the T-54s and T-55s of the Soviet Union and Warsaw Pact as well as to South Korea but was never sent to South Vietnam mainly due to unfavorable terrain and the general lack of significant numbers of North Vietnamese armor. In May 1961 Army Chief-of-Staff General George Decker announced that the European Command had been receiving the M60 to replace older tank inventory.[58] By October the Seventh Army was outfitted with many of the tanks. A total of 2,205 M60s were built between June 1959 and August 1962.[51] Some M60/E60 tanks were later transferred to Israel and participated in the Yom Kippur War. Some were repurposed as AVLBs.

M60E1 pilot number 1 during preliminary tests at the Detroit Arsenal Test Center 19 May 1961. The machine guns are not installed.

Development

The program to develop the M60A1 was approved in early 1960 in conjunction with abandoning further development of the advanced composite armor and the closure of the T95 Medium Tank project.[59] The first proof of concept attempt to mate a modified M60 hull with the T95E7 turret took place in March 1960. The turret, even without the siliceous cored armor, provided improved ballistic protection. Additional space for the turret crew was also made available by using the M140 mount thus moving the cannon 5 inches forward.[59] The first two prototypes (Pilot 1 and 2) were ready in May 1961 and the third (Pilot 3) in June 1961, when the vehicle also received its official prototype designation as the M60E1.[60] These vehicles were built by Chrysler Defense. Pilot 1 was sent for evaluation at the Eglin Air Force Base climatic hangar, while Pilot 2 was tested at the Yuma Test Station,[61] and Pilot 3 underwent field trials at Fort Knox.[16] On 22 October 1961, the M60E1 was officially accepted in service under the designation of Tank, Combat, Full Tracked: 105-mm Gun, M60A1.[62] Production began on 13 October 1962 when the Army placed an initial order for 720 of the tanks for 61.2 million dollars.[63]

M60A1 tank on display at Fort Knox KY in 2011

Features

In addition to the new turret design, the hull was upgraded. The hull's upper glacis armor was increased from 3.67 inches to 4.29 inches at 65 degrees while the turret sides went from 1.9 inches to 2.9 inches at their apex.[64] This brought the frontal armor up to the same 10" line of sight armor standard of the M103 heavy tank. A mushroom-shaped fume extractor was placed at the rear left of the turret bustle to vent smoke produced from firing the main or coax guns out of the vehicle. The addition of a shock absorber on the second roadwheel pair was also accompanied by a slight relocation of the first return roller. These modifications were needed due to the increased weight of the M60A1 turret as well as the additional hull armor.[65] The ammunition load for the main gun was increased to 63 rounds. Round storage was distributed between the turret bustle, with 15 ready rounds of various types were stowed and accessible for the loader, and the rest are stored inside safe containers on the hull floor.[40] The uncomfortable wire mesh seats for the loader and gunner were replaced with padded ones. The brake and accelerator pedal and gauges were also rearranged for more efficient and comfortable operation while the steering wheel was replaced by a T bar steering control.[66] The engine and power train were supplied by the Continental AVDS-1790-2A engine and the CD-850-5 cross drive transmission and using the T97 track assembly.

Improvements to the electronics package for this version included an improved electro-mechanical traverse assembly and an AN/VSS-1(V)1 IR searchlight above the gun shield.[67] The M19 FCS consisted of the M17A1 coincidence rangefinder, M10A1 ballistic drive and the mechanical M19E1 ballistic computer for the gunner.[45] The M60A1 tank uses the M68E1 variant of the gun carried in the M140 mount.[28] The M68E1 gun shares the same firing characteristics as the M68. It featured several design improvements including an updated gun hydraulic configuration, a stabilization upgrade for the gun, a gun elevation kill switch for the loader, improved ballistic drive and other component refinements.[29]

Upgrades

As the development of a new main battle tank stalled with problems and cost escalating quickly, the M60A1 was forced to serve longer than originally intended with production lasting almost 20 years. In that time span, numerous product improvement programs were put forward. As the major changes were incorporated into the production line, the vehicle model designations were changed. The first of which was Top Loading Air Cleaner (TLAC) in 1971. This reduced dirt and dust ingestion, which increased engine life as well as allowing for easier servicing of the engine.[68] Early TLAC panels were made from aluminum and were vulnerable to damage from small arms fire.[55] Next came Add-On Stabilization (AOS) that was introduced in late 1972.[68] This was an add-on kit made to fit with minimum modifications to the existing hydraulic gun control system. The add-on-stabilization system provides stabilization control for both gun elevation and turret traverse. It provides the gunner with the capability of aiming and target tracking and also improved surveillance of the battlefield terrain by the gunner while the tank is moving.[55] It may be used in any one of three modes of control: (1) power-with-stabilization-on, (2) power-with-stabilization-off, and (3) manual. In the power-with-stabilization-on mode, the gunner's aim on target is automatically retained while the vehicle is in motion. This mode provides a fire-on the-move capability. The power-with-stabilization-off option eliminates needless exercise of the stabilization system and provides a backup power mode. The manual back up system permits the crew to aim and fire the weapons should the electrical/hydraulic subsystems fail.[55] At a range of 2000 meters, hit probabilities of better than 70% from a moving M60A1 were obtained in Aberdeen[55] test results while without a stabilizer it was essentially zero. M60A1s with this upgrade were designated as the M60A1(AOS). The T142 track was fielded in 1974 which had replaceable rubber pads, better end connectors and improved service life.[69] M60A1(AOS)+ was the denotation for M60A1s equipped with the TLAC, AOS and the T142 track.[55]

Introduced in 1975 the Reliability Improved Selected Equipment (RISE) was a comprehensive upgrade of the M60A1 hull as well as integrating the previous TLAC and AOS upgrades. It included the upgraded AVDS-1790-2C RISE diesel engine and CD-850-6 transmission that featured several changes in order to improve service life and reliability. A new 650 ampere oil-cooled alternator, a solid state regulator and new wiring harness with more accessible disconnectors was also incorporated into the hull's electrical system[69] as well as armored steel TLAC panels and the return to the use of steel roadwheels and return rollers. They were denoted as M60A1(RISE).[55] The 1977 fielding of the passive M32E1 sight for the gunner and M36E1 periscope for the commander as well as the M24E1 IR night vision block for the driver provided second generation night vision capabilities for M60A1 and RISE tanks. These new passive gunner's sight and commander's periscope provide recognition capability at longer ranges and at relatively low night light levels (1/2 moonlight). Under starlight conditions, they will provide recognition beyond 500 meters with the use of an IR searchlight.[55] During 1978 kits for the mounting of the M239 smoke grenade launchers and the mounting of the M240 as the coaxial machine gun was fielded. The development of the M735 APFSDS ammunition required a cam update to the gun's mechanical ballistic drive for accurate firing. M60A1s configured to this standard were denoted as M60A1(RISE)+.

A US Army M60A1 RISE Passive tank maneuvers through a narrow German village street while participating in REFORGER 1982.

The M60A1(RISE) Passive featured the implementation of all previous updates plus Kevlar spall liners for the turret, AN/VVS-2 passive night vision block for the driver, a deep water fording kit, the capability to mount Explosive Reactive Armor (ERA)[70][62] and the AVDS-1790-2D RISE engine with CD-850-6A transmission and a Vehicle Engine Exhaust Smoke System (VEESS) that visually obscured the area around the vehicle. The VEESS smokescreen system does not provide protection against infrared, thermal or laser detection. The two six-barreled, electronically fired M239 smoke grenade launchers, one on each side of the main gun and replacement of the coax machine gun with the M240C were implemented in late 1978. The smoke grenades contain a phosphor compound that masks the thermal signature of the vehicle to the enemy. They were denoted as M60A1(RISE) Passive.[55]

Over the period of M60A1 tank production, several essential engineering changes were incorporated. Many of these miscellaneous changes are to improve the system safety, reliability, maintainability and increase mission performance. The M60A1 tank Hull/Turret PIP Update Kit includes those items that could not be readily identified with basic major product improvements and to incorporate essential engineering changes that had occurred during M60A1 tank production. The update program included engineering changes and minor product improvements which were not part of specific product improvements, but were required to upgrade early vintage M60A1 tanks up to the current M60A1(RISE) production configuration.[55] Additionally the Hull PIP Update Kit was applied to the M48A5.

The M60A1 was in production from October 1962 until May 1980[16] and was extensively used by the US Army and Marine Corps as well as being widely exported to foreign governments. A total of 7,948 M60A1s (all variants including E60A) were built.[71] Many of them were later converted to the A3 standard.

During the early 1960s there was some debate regarding the future of main tank weaponry, largely focusing on conventional kinetic energy rounds versus missiles. In the early 1960s it was generally accepted that the maximum effective range of the M68 gun was between 1800 and 2000 meters. The XM-13 missile system had proven itself viable, obtaining over 90% first round accuracy up to 4000 meters. But the development of a main-battle tank variant was bogged down by having too many design proposals. In response, studies were made in August 1961 to retrofit existing M60 tanks with a weapon capable of firing both conventional HEAT (High-Explosive Anti-Tank) rounds and launching ATGMs (Anti-Tank Guided-Missiles).[72] Three M60E1 tanks with T95 turrets were modified to permit the installation of the 152mm XM81 gun-launcher. Mounted on former M60 hulls, they were to provide test beds for the evaluation of the Shillelagh weapon system. Although this system was the preferred armament for the MBT-70, by late 1961 problems with the XM13 missile required that the program be reorganized. The missile was reclassified as an applied research project and it was obvious that there would be some delay before it would be available for service.[73] On 10 January 1962, representatives from various ordnance organizations met at the Ordnance Tank-Automotive Center (OTAC) to review armament systems that might be suitable replacements, if the Shillelagh missile could not be developed in a timely manner. Time was particularly critical for the AR/AAV (the XM551 Sheridan) which required a decision on the armament by April 1962. The possible delay was not as serious for the MBT-70 since the program was limited to conceptual design and component development. The requirements also differed for the tank because of its ability to carry a much heavier weapon system. Several backup weapons were also under consideration and concept studies were prepared showing their application to the MBT-70 concepts. The 152mm gun-launcher XM81 also was considered without the missile depending only on the combustible case conventional ammunition. It was expected that the Shillelagh or some other missile then could be introduced at a later date. The 105mm gun M68 as standardized for the M60 tank was considered as an alternate armament system. It had the advantage of being immediately available and its ammunition was already in production. Of the several turrets drafted, one of the earliest was the driver-in-turret integrated fighting compartment. This design was further developed using the MBT-70. Another proposal was a more compact turret design of the T95E7.[74]

Development

Conceptual drawing of the XM66 with Type C turret

During the development of the M60A2, three different turret types were considered, the Type A, Type B and Type C. The Type A turret would be constructed based on the T95E7 turret and then further modified and produced as the Type B standard. The Type C turret was essentially a larger M551 Sheridan-style turret. A mock-up of this turret was built, but the design was never seriously considered and soon abandoned. All of these conceptual variants were referred to as the XM66. On 10 January 1964, the Army reviewed all three variants and selected the Type A variant for further development. Initially two Type A turrets were built in 1964.[75] The M60A1 hull was used starting in 1966 to develop the new compact turret design using the 152mm M162/XM81E13 rifled barrel main gun. These developmental tanks were designated as the M60A1E series.[76]

The M60A1E1 referred to vehicles based on the modified T95E7 Type A turrets with M60 hulls used through 1965. The M60A1E1 variant was used to evaluate the XM81 dual purpose gun and its compatibility with the XM13 Guided Missile, Armor Defeating together with the XMTM51 training round. They used a modified M60A1/T95E7 turret. During the early testing of the XM81 main gun it was noted that misfires and premature detonations of the M409 conventional case ammunition were caused by unburnt propellant in the bore and breech. This flaw was often catastrophic as it set off the projectile in the barrel as it was fired.[77] To remedy this the guns were equipped with a traditional fume extractor on the barrel.[78] The XM81 Gun/Launcher also experienced frequent faulty breaches, often not closing correctly during a missile firing, allowing the exhaust of the launching Shillelagh to vent hot noxious gasses into the crew compartment.[72]

M60A1E2 tank prototype with Type B turret.

As the M60A1 hull became available in 1966, it was decided to upgrade these prototype vehicles to the M60A1 hull standard. Vehicles using the M60A1 hull and chassis received the M60A1E2 designation, and were used to develop the Type B compact turret and the XM81E13 gun variant.[79] The M60A1E2 finalized the turret design with the use of a compact turret which reduced exposed frontal area by 40% compared to the M60A1 and continued development of the M51 Missile Guidance System (M51MGS).[77] These were later standardized as the M60A2. Initial plans called to retrofit the turret of every M60 with the new A2 turret, and use them in the mobile anti-armor role alongside the M60A1 tanks. But the continual technical and reliability difficulties with the dual purpose gun caused this to be abandoned. The M60A1E3 variant was a prototype mounting the M68 105 mm rifled gun to the turret of the M60A1E2. This was evaluated due to several earlier faults noted in the M60A1E1's main gun. Compared to the Shillelagh system, the use of the 105mm gun increased the overall tank weight by about 1700 pounds.[80] The M60A1E4 was a conceptual variant that explored the use of various remote controlled weapons, including a 20mm gun as secondary armament. A mock-up of this design using the Type C turret was constructed. All variants of this series underwent evaluations and trials at the Aberdeen Proving Grounds.[4] The M60A1E2 was finally accepted by the Army in 1970 and given the designation Tank, Combat, Full Tracked: 152-mm Gun/Launcher, M60A2.[81] Initial orders were submitted by the Army in 1971 however production did not start until 1973 and continued until 1975. All were built at the Chrysler Tank Plant in Warren, Michigan with a total of 540 M60A2s produced.[4] The M60A2 was intended to serve as the stop-gap solution until its projected replacement, the MBT-70 completed its development.[82] The M60A2 was deployed to Army units in Europe starting in June 1975 when B Company, 1-32 Armor Battalion received its first M60A2 tanks.[83]

Early version of the M60A2 at AAF Museum

Features

The M60A2 featured a unique low profile turret, mounting the M162 Gun/Launcher that drastically reduced the turret's frontal arc in comparison to the A1's. It consisted of a large disk with a narrow channel in the center with each crew member in the turret having their own hatch. The gunner and loader were located to the right and left of the gun, respectively, and the commander was in a turret basket up and behind the main gun. As a result, each crew member was effectively isolated from one another with the gunner and loader separated by Shillelagh missiles in their storage position. The commander was in the rear compartment under a large redesigned cupola, which somewhat negated the low profile silhouette of the turret.[72] The M162 gun was fully stabilized in both turret traverse and gun elevation using the same upgrade kit as the M60A1 AOS, allowing the gunner to effectively scan the battlefield while the tank was in motion. This system could be used by the gunner to engage targets with unguided M409 rounds while the vehicle was in motion, but the tank had to remain stationary when firing and tracking an MGM-51 missile.[72] The turret interior also received Kevlar spall liners. Four M226 smoke grenade launchers were mounted on each side of the turret bustle.[77] Additionally there was a mounting point to the left of the turret for an AN/VSS-1(V)1 Infrared Spotlight and M19E1 IR periscope providing first generation night vision for night operations. A basket was fitted to the rear of the turret to stow the spotlight when not in use. Late production versions replaced the bore evacuator with the Closed-Bore Scavenger System (CBSS), a compressed air system that pushed the fumes and gasses out of the muzzle when the breach was opened.[84] Initial production M60A2s used the M60A1 hull powered by an AVDS-1790-2A TLAC engine, CD-850-5 cross-drive transmission and the T97 track assembly. Many of these hulls were later upgraded to the RISE standard.[72]

The M51 Missile Guidance System (MGS) for the Shillelagh missiles was designed by Ford's Aerospace Division. The M51 MGS consisted of an infrared (IR) direct beam guidance and control system to track the missile mounted to the turret over the mantel of the gun[85] with a telescopic sight and a Raytheon AN/WG-1 Flashlamp Pumped, Ruby Laser range finder,[86][87] accurate to 4,000 meters,[83] for the gunner. The gunner aimed the cross-hairs in his direct telescopic sight at the target and fired the missile. After acquiring a target a small charge would propel the missile out of the barrel, the missile's solid-fueled sustainer rocket then ignited and launched the Shillelagh. For the time of flight of the missile, the gunner had to keep the cross-hairs pointed at the target. A direct infrared beam missile tracker in the gunner's sight detected any deviation of the flight path from the line-of-sight to the target, and transmitted corrective commands to the missile via an infrared command link. The MGM-51A was stabilized by flip-out fins, and controlled by hot gas jet reaction controls.[88] The gunner also employed an M219 (later replaced with a M240C) to the gun mantle's right with 2,000 rounds.[89] The commanders cupola was redesigned causing the M85 to be mounted in the inverted position in order to provide access to its feed cover and mounted a single M34 periscope carrying 600 rounds.[84] The M60A2's combat load for the M162 main gun consisted of 33 M409 rounds and 13 MGM-51 Shillelagh missiles.[77]

Flaws

This weapon system had several drawbacks. First the gunner had to keep the target in the crosshairs of the sight during the entire flight time of the missile.[90] This meant that only one target could be tracked and engaged at a time. Furthermore, the M60A2 could not fire or track a missile while moving.[77] Secondly was the high minimum range of about 730 m (2,400 ft). Until the missile reached this range it flew beneath the tracking system's infrared beam and could therefore not be guided by the infrared command link. Also minimum range was slightly above the maximum effective range of the M60A2's conventional unguided munition, this created a dangerous gap area that could not be adequately covered by fire known as a "dead zone". It was also discovered that structural cracks in the barrel occurred after several missile firings. This defect was traced to a flaw in the longitudinal key, which fitted into a keyway inside the gun barrel. It was determined that a less deep key would significantly extend the service life of the barrel. The Missile Control System was also very fragile owing to its dependence on vacuum tubes which often broke when firing the gun. Finally a Shillelagh missile was considerably more expensive than the M409 round. The vehicle was one of the most technologically complex of its era, eventually garnering an unofficial nickname of "Starship".[77] This also contributed to its failure, largely due to difficulties with maintenance, training, and complicated operation.

The M60A2 proved a disappointment, though its technical advancements would pave the way for future tanks. Its intended successor, the MBT-70, was canceled in 1971 and its funding diverted into the conceptual development of the XM1 Abrams.[91] The Shillelagh/M60A2 system was phased out from active units by 1981, and the turrets scrapped. The main replacement for the Shillelagh missile in the mobile anti-armor role was the more versatile BGM-71 TOW.[85] Most of the M60A2 tanks were rebuilt as M60A3s, or the hulls converted to armored vehicle-launched bridge (AVLB) vehicles[84] and M728 Combat Engineer Vehicles with a few M60A2s retained as museum pieces.[92]

US M60A3 on Display in Lake Charles, Louisiana in April 2005

Development

Due to the rapidly developing advancements in anti-armor capabilities and solid state electronics of the 1970s, along with the general dissatisfaction of the M60A2, an upgrade of the M60A1 was needed. In 1976 work began on the M60A3 variant which featured a number of technological enhancements and increasing the turret armor.

Features

Two M60A3TTSs of the US Army near Giessen, West Germany 1985

The M60A3 version of the M60-series had the same mobility, performance, and weapons systems as the M60A1 RISE and RISE Passive tanks and incorporated all of their engineering upgrades, improvements and capabilities. In addition, the armor protection for the turret was increased to 330 mm on the gun mantle and to 276 mm on the turret face.[11] The electronics and fire control systems were greatly improved. The turret's hydraulic fluid was replaced with a non-flammable one. This updated turret configuration was mated to the M60A1 RISE hull using the AVDS-1790-2D RISE engine and CD-850-6A transmission along with a Halon fire suppression system.[93] It was designated as the Tank, Combat, Full Tracked: 105-mm Gun, M60A3.

The M60A3 tank was built in two configurations. The earlier version, sometimes referred to as the M60A3 Passive,[55] uses the same passive gunner's sight as the A1 RISE Passive and the latest version has a Tank Thermal Sight (TTS). The M60A1, RISE, and RISE Passive tanks used a coincidence rangefinder and the mechanical M19 ballistic computer. The M60A3 uses a laser based rangefinder and the solid state M21 ballistic computer. The M21 FCS for the M60A3 was made up of a Raytheon AN/WG-2 flash-lamp pumped ruby-laser based range finder, accurate up to 5000 meters for both the commander and gunner,[94] a solid-state M21E1 gun data computer incorporating a muzzle reference sensor and crosswind sensor, ammunition selection, range correction and superelevation correction were inputted by the gunner, an improved turret stabilization system along with an upgraded turret electrical system and solid-state analog data card bus. The M10A2E3 ballistic drive is an electro-mechanical unit. The commander had an M36E1 passive periscope and the gunner an M32E1 passive sight.[55] The TTS configuration replaced the gunner's sight with the Raytheon AN/VSG2 Tank Thermal Sight (TTS), a Mercury-Cadmium-Telluride (HgCdTe) IR detector. This sight allows the gunner to see through fog, smoke and under starlight conditions without the aid of an IR searchlight. This system provided improved first round hit capabilities.[55]

US Army crew aims its M60A3TTS during NATO Exercise Certain Sentinel 1986. Note the TTS IR detector over the gun and the opening for the laser range finder in lower gunner's periscope.

The first M60A3s were assembled at the Detroit Arsenal Tank Plant in February 1978[55] where the first of a low-rate of initial production quantity of 296 M60A3s were produced through October[94] with fielding to Army units in Europe starting in May 1979.[55] The M60A3 was seen by the US Army as a stop-gap measure as the development of the XM1 Abrams MBT was already well advanced with fielding to Europe planned to start in 1981 and notified FMS customers of its near-term plans to discontinue M60-series tank production.[55] In March 1982 General Dynamics Land Systems Division purchased Chrysler Defense. The procurement of M60A3 and M60A3 TTS tanks for the Army concluded and hull production ceased in May 1983[55] with a total of 1,052 M60A3 and TTS tanks built as new vehicles. However the conversion of earlier models to M60A3/E60B tanks continued for Foreign Military Sales (FMS) with the last tanks delivered to Israel in May 1986[95] and a conversion total of 3,268 E60Bs. These late-production examples were upgraded from existing surplus inventories of M60A1 RISE tanks. The Army also increased its M60A3 TTS fleet through the M60A1 tank conversion program and the M60A3 tank field retrofit program conducted by the Anniston Army Depot and the Mainz Army Depot (MZAD). Depot field teams retrofitted all of the Army's 748 M60A3 tanks to the TTS configuration by the end of 1984. In addition, both depots converted a total of 1,391 M60A1 RISE tanks to the M60A3 TTS.[95] These M60A1 Hull/Turret PIP conversion programs concluded in 1990. Italy, Austria, Greece, Morocco, Taiwan and other countries upgraded their existing fleets with various E60B component upgrades under several FMS defense contracts with Raytheon and General Dynamics during the mid to late 1980s.[93] In 1990, M60A3/E60Bs from Army surpluses were sold to Oman, Bahrain, and Saudi Arabia.[5] The M60A3 replaced the M60A1 in Army and any remaining M48A5s in National Guard service on a one-for-one basis but the Marine Corps continued to use the M60A1 RISE Passive until they were withdrawn from combat use in 1991.[96] They were phased from National Guard service between 1994 and 1997, being replaced with the M1 MBT. Additionally the Detroit Tank Plant was closed in 1996 with production of the M1A1 Abrams continuing at the Lima Tank Plant in Ohio.

M60s for use in foreign military service were designated as the E60 series by the US Foreign Military Sales (FMS). These were essentially M60s with minor modifications requested by approved foreign purchasers. Some of the modifications included removal of the M19 cupola, different models of machine guns, electronics, fire control systems or radios, external armor plates, smoke launchers and power packs.[97] Israel purchased many of these tanks forming the basis for the Magach 6 series.

This series included the following designations:

• E60: modified M60 variant for non-US service
• E60A: modified M60A1 variant for non-US service
• E60B: modified M60A3 variant for non-US service

The M60A2 was never approved for foreign sales.

A US Congressional Report in November 1993 stated that there were 5,522 serviceable M60A1 and M60A3 tanks in the US Army's inventory available for sale or transfer to US allies or foreign nations. Of these 111 were in Korea, 1,435 were in Europe, and 3,976 located in CONUS. The average age of these tanks was 16 years and an expected peacetime service life of 20 years. The average price was US$212,898 per tank as is, without radios or machine guns and they were not mechanically overhauled. Tanks located in Korea were inspected and sold to Bahrain and Taiwan. Of the 1,435 tanks in Europe, 1,311 have been cascaded to other NATO countries under the terms of the Conventional Forces Europe Agreement (CFE), 18 reserved for non-combat use and 106 returned to CONUS. Egypt inspected 411 tanks at Fort Hood and 91 at Fort Knox and tentatively selected 299 of those. An additional inventory of tanks from the CONUS M60 fleet were available at the same unit price for other approved purchasers.[98]

The United States chose not to pursue further upgrades to the M60 tank series after 1978. Its near-term replacement by the Army with the M1 MBT being scheduled to start production 1980. M60 series tanks were phased out of US service by 1997 and OPFOR(S) training use in 2005. Together with the large number of M60MBTs still in foreign service and a large US Army surplus inventory, several upgrades for the tank were offered starting in 1985. There are three basic approaches to upgrade decisions for the M60MBT. Some countries, such as Taiwan and Jordan, have sought to modernize the M60 as a frontline main battle tank. Turkey is seeking a middle-ground, keeping it useful as it develops more modern designs. Other countries, such as Egypt, Saudi Arabia and Thailand are modernizing their M60 fleets for counter-insurgency type operations. While the market for M60 modernization is somewhat limited, because the tank is generally operated by poorer countries or has been relegated to secondary tasks, other companies have come up with more advanced SLEP upgrade solutions. Additionally, several countries also funded their own design upgrades, notable examples are the Magach, Sabra and Phoenix variants. In 2005, M60 variants were in service with Egypt, Greece, Israel, Jordan, Turkey, Taiwan and some 20 other nations to varying degrees.

General Dynamics Super M60 prototype, 1985

The High Performance M60, also called Super M60, was a comprehensive update package for the M60A1 and A3 tanks, first offered in 1985 by Teledyne Continental. The vehicle was developed as a private venture for the export market and was never evaluated for US military service. Unofficially called the M60AX, the upgrade offered to increase the protection, firepower and mobility for the M60A1 and A3 tanks.[99]

Although the US Army chose not to adopt the installation of a new power pack or suspension system in the M60 series, General Dynamics formed a co-operative private venture with Teledyne Continental to develop a comprehensive upgrade package. The Super M60 prototype was based on an M60A1 leased from the US Army. It featured the AVCR-1790-1B engine producing 1200 hp coupled to a Renk RK-304 transmission with 4 forward and 4 reverse gears.[100] The torsion bar suspension system of the M60 was replaced with a hydropneumatic suspension system (HSS) developed by the National Waterlift Company as seen on the HIMAG, General Motors XM1, and the Jordanian Centurion (Tariq). Over the M60A1, the Super M60's top speed increased to 45 mph and power/weight ratio increased to 23.1 hp/t, despite the 9500 lb increase in weight. Survivability was enhanced with a layer of Chobham spaced applique armor built around the turret and frontal arc of the hull that noticeably changed its appearance. The applique armor comprised of an outer layer of high-hardness steel armor panels and an inner layer of ceramic inserts covering the base M60A1 vehicle. Track skirts comprised of Sitall and high-hardness steel for the hull sides as well as Kevlar spall liners for the fighting compartment were added.[101] Like the vehicle it is based on, it retained a crew of 4: the commander, loader and gunner positioned in the turret and the driver in the front of the hull.

Magach 7C in Yad la-Shiryon museum, Latrun.

The weapons of the Super M60 are similar to those of the M60A3. The main gun is the rifled 105 mm/L55 M68A1E2 with a longer XM24 tube and a thermal sleeve, the same weapon used on the M1 and M1IP versions of the M1 Abrams with 63 rounds. The 7.62 mm M73 coaxial machine gun used on the M60A1 was replaced with a 7.62 mm M240C, with the same number of rounds. The M19 cupola was replaced with a low silhouette model with a pop-up hatch for the commander and a 12.7 mm M2HB machine gun on a pintle mount with 600 rounds. The Fire Control System (FCS) used was designated the Advanced Laser Tank Fire Control System (LTFCS). The FCS configuration was largely similar to that used on the M60A3, but instead of replacing the optical rangefinder with an AN/VVG-2 laser rangefinder, a Nd:YAG laser emitter was installed on the roof and the M35 gunner's sight was modified to include a laser visual unit.[101] Also, the stabilization configuration was changed to that of the M1 Abrams where the sight itself was fully stabilized and the gun followed the sight. The prototype did not have an optical range finder but one could have been easily installed.

After initial tests with only the new engine and suspension, additional modifications such as the armor upgrade intended to increase protection from shaped charged projectiles were applied.[102] Testing conducted not only showed that the new suspension system smoothened the off-road ride, but also allowed the Super M60 to handle well in spite of its considerable weight increase over the original M60A1. As one of the first upgrade packages offered for the M60 series, the Super M60 prototype demonstrated the potential for upgrading the M60A1/A3 and was offered by Teledyne Continental as one of their many possible upgrade packages. Even though this update package offered M60 users an opportunity to dramatically increase the combat capabilities of their tank fleets, no country ever bought the update and the program effectively ceased by the end of the Cold War. Only one prototype was built. The overall failure of the Super M60 program was likely due to the lack of immediate necessity for such a vehicle.[102] This design was similarly developed independently by Israel in their Magach 7 series. Additionally the German company Krauss-Maffei Wegmann offered the Super M48 MOLF, applying this design to the M48A2/A3.[103]

M60-2000/120S MBT prototype

The General Dynamics Land Systems (GDLS) M60-2000 or 120S was an upgrade of the M60A1 tank. The development of the M60-2000 was primarily due to the large number of M60 Main Battle Tanks in service with many Middle Eastern nations unable to afford a sufficient force of more modern main battle tanks. The upgrade was marketed at those M60 users with the industrial capability to convert the tanks themselves. The M60-2000/120S was a GDLS supplied conversion kit that married the M1A1 turret of the M1 Abrams to the M60A1 RISE hull, offering many features of the M1A1 Abrams to existing M60 users at a reduced cost.

It was first referred to the M60-2000 Program and design work began in late 1999 by General Dynamics Land Systems as a private venture for the export market and was never evaluated for US military service. Later the M60 designation was dropped because of the extensive changes and to highlight this as a new vehicle to potential customers thus changing the name to the 120S Project. The M60-2000 was test-marketed during 2000 and a number of countries in NATO and the Middle East were briefed on the vehicle. Following customer feedback, detailed engineering work was carried out and in December GDLS decided to build a functional prototype.[104] In August 2001 the company rolled out the fully functional prototype of the 120S MBT at their Detroit, Michigan, facility. The prototype was shown at the IDEF Exhibition held in Turkey in October 2001.

The 120S was initially aimed at the Turkish Land Forces Command (TLFC) M60 upgrade requirement but this competition was subsequently won by IMI Military Industries with their Sabra II upgrade. The Egyptian Army was considering this offer until it was finally rejected in favor of a licensed contract to build M1s in Egypt.[105] Only one prototype was made. As of early 2009 there were no sales of the 120S MBT and was no longer mentioned in General Dynamics marketing literature. The prototype was disassembled and the hull and turret returned to the US Army in 2003.[106]

The M60 Phoenix Project was Jordan's modular upgrade of the M60A3TTS to better address both immediate and emerging threats to the M60MBT.[107] The tank is armed with a RUAG Land Systems L50 120 mm smoothbore Compact Tank Gun (CTG) with a firing rate of 6-10 rounds per minute. 20 ready rounds are stored in the turret bustle.[108] The M21 FCS is replaced with Raytheon's Integrated Fire Control System (IFCS). The system consists of an eye safe laser rangefinder, second generation night sight, digital ballistic computer, cant sensors and a MIL-STD 1553 data bus. The M10 ballistic drive is upgraded with a fully electrical superelevation resolver.[107] The maneuverability and acceleration of the Phoenix is improved with the use of the General Dynamics AVCR-1790-2C engine producing 950 hp increasing available power by 20%, an upgraded CD-850-B1 transmission, new air cleaner and air induction systems, improved suspension and new and improved final drives. Survivability is improved through the addition of various modular armor protection schemes for both the M60's turret and hull. The upgrades include armor protection with STANAG 4569 Level 6 protection plates to the frontal arc, passive and reactive armor panels and side skirts and slat armor added to the bustle, protecting the rear of the turret from RPG attack. The protection scheme can be reconfigured to changing threat conditions. It also has a 12 tube High Speed Directed Launcher (HSDL) smoke screen system using a multi-spectral smoke hardxill providing protection against thermal detection.[109] On 15 April 2004 Raytheon Company was awarded a $64.8 million contract by the Jordan armed forces to upgrade 3 tank battalions.[110]

Raytheon has been working with Jordan's King Abdullah II Design and Development Bureau (KADDB) on its Phoenix Level 1 Independent Fire Control System (IFCS) upgrade and Level 2 Lethality upgrade efforts for the M60 main battle tank. Some of the upgrades included passive spaced armor packages, IR jammers and an ammunition containment system for the turret bustle. A $46.6M contract with the Jordan Armed Forces was authorized in 2012 to upgrade one battalion of their Phoenix main battle tanks.[111]

Raytheon in conjunction with other partners offered the M60 Service Life Extension Program (SLEP) for the M60A3 in May 2016.[112] It has been marketed for export to nations that need the performance improvements to take on modern armor threats. The SLEP is offered as a collection of modular upgrades for the tank's firepower, mobility, and protection. This allows for SLEP customization to each user's needs. Its firepower improvements features the 120-mm M256/L44 smoothbore main gun as used on the M1A1 Abrams. It is fitted with a load assist system allowing for a firing rate of 6 to 10 rounds per minute and 20 ready-rounds in the turret bustle. The Raytheon Integrated Fire Control System (IFCS) integrating an eye safe laser rangefinder, second generation gunner's night sight, digital ballistic computer, cant sensors, a fully electrical superelevation resolver and a MIL-STD 1553 data bus, giving the system capabilities similar to the M1AD standard. Other turret upgrades offered are the Curtis-Wright Gun Turret Drive and replacing the M19 cupola with a Hitrole remote controlled weapon system, that enables 360° panoramic surveillance from a secure position inside the tank armed with a M2HB .50cal machine gun.[113]

Suspension and mobility upgrades include an upgraded AVCR-1790-2C engine producing 950 hp and improved hydropneumatic suspension. The installation of an Automatic Fire and Explosion Sensing and Suppressing system (AFSS) that improves soldier survivability and protects the engine compartment as standard. Upgraded armor protection with STANAG 4569 Level 6 protection plates to the frontal arc and side skirts and slat armor added to the bustle, protecting the rear of the turret from RPG attack. These changes increased the vehicle weight to 62-63 tons.[114]

Leonardo M60A3 prototype, 2017

The Leonardo M60A3 is a modular SLEP upgrade for the M60MBT offered in 2017 by the defense company Leonardo DRS. The upgrade is intended to offer nations already operating the M60 a modular upgrade solution for their vehicles to offer capabilities more in line with third-generation main battle tanks. It was unveiled 17 October 2017 at the Bahrain International Defense Exhibition and Conference (BIDEC). It has been marketed as an alternative upgrade to the Raytheon SLEP upgrade for M60MBT modernization.

Upgrades offered in this package include a new 120/45 gun from the Centauro II that offers a weight saving of 500 kg over the older 120/44 gun due to a redesigned light alloy cradle and muzzle brake. The old commander's cupola is completely removed and replaced instead with an armored circular ballistic plate protected with slat armor. This also offers a weight reduction compared to the original M19 cupola as used on the M60A3. For close defense, the turret is also fitted with the HITROLE-L 12.7mm remotely operated weapons system.[115] The turret has been refitted with a new set of hydraulic and servo control improving performance. The rest of the vehicle is completely overhauled including the torsion bars, brakes, fuel supply, electric system, wheels, seals, paint, and smoke grenades. The vehicle has also been retrofitted with the Automatic Fire and Explosion Sensing and Suppression System (AFSS). It is equipped with the LOTHAR gun sight, DNVS-4 Driver's Night Vision Sight and TURMS digital fire control system. a daytime TV camera, and an eye-safe Laser range finder. IED jamming systems and a laser warning receiver systems developed by Leonardo are optionally offered.[116]

Armor improvements include a whole new passive protection suite fitted around the M60's existing cast armor turret and hull that is claimed to meet STANAG Level 6 standards. Protection for the turret is optimized for protection against kinetic energy (KE) weapons and artillery across the frontal arc. The hull to is upgraded to the same standard with the protection covering the hull sides extending to the third roadwheel. For the rear of the turret, slat armor is provided with an emphasis on protecting against the RPGs.[117]

Mobility is improved via either a full refurbishment of the existing power packs or an upgrade. The new powertrain offered is stated to deliver up to 20% more power without high costs and avoiding the need for any modifications to the existing hull. This AVDS-1790-5T 908 hp engine replaces the 750 hp engine and is connected to an upgraded CD-850-B1 transmission.[117] It was unveiled at the Bahrain International Defense Exhibition and Conference (BIDEC) at Manama, Bahrain in 2017.[118]

• M60 AVLB: armored vehicle-launched bridge with 60-foot (18 m) scissors bridge mated to the M60 hull.
  • M60 AVLM: M60 Armored Vehicle Launched Bridge (AVLB) with up to 2 vehicle mounted M58 MICLICs. To employ the system, the vehicle cannot be carrying a bridge. The system consists of an M147 firing kit, an M58A3 line charge and a 5-inch MK22 Mod 4 rocket.[148] The line charge is 350 feet long and contains 5 pounds per linear foot of C-4 explosive.[149] In the event a MICLIC fails to detonate normally, it can be manually activated by time-delay fuses every few feet along the length of it.
• M60VLPD 26/70E: Spanish Army bridgelayer based on the M60 with "Leguan bridge system". 12 converted from M60A1 hulls.
• M60 Tagash AVLB: Israeli variant of the M60AVLB. Upgraded with Merkava- based track and suspension, upgraded engine and 2 Tzmed tandem bridge sections.[150]

XM1060 ROBAT circa 1982

• XM1060 ROBAT (Robotic Obstacle Breaching Assault Tank): A former M60A3 tank without its turret configured to clear mine fields and mark cleared lanes and also to detect chemical, biological, and nuclear agents. It was fitted with a M1 MRCS mine roller and 2 M147 Line Charge Firing Kits.[151] The crew may operate the vehicle via remote control by a fiber-optic video link, or the commander and driver sit in tandem in two armored pods fitted with an NBC protection system.[152] The ROBAT fires an M58 MICLIC line charge filled with explosive over a minefield and then proofs the lane with a M1 MCRS. A Cleared Lane Marking System (CLAMS) dispenses day or chem-illuminescent light sticks from the rear to mark the cleared lane.[153] Developed during the early 1980s and was canceled by 1988.[154]

A Panther MDCV equipped with an M1 MCRS prepares to lead a column of vehicles down a road near McGovern Base, in Bosnia and Herzegovina on May 16, 1996, during Operation Joint Endeavor.

• M60 Panther MDCV (Mine Detection and Clearing Vehicle): M60 without a turret fitted with countermine systems used by US forces during operations Joint Endeavor and Joint Task Force Eagle. The Panther can have a 2-man crew or be used as a remotely controlled vehicle.[155] It is used to proof lanes and assembly areas.[156] The system consists of a turretless M60 tank, Israeli Pearson mine rollers, an antimagnetic actuating device, and a Standardized Teleoperation System (STS) that is mounted in a separate vehicle. Additionally, a remote video camera allows the operator to see the road ahead.[157][60] Only 6 built from former M60A3s, withdrawn from use by 2000 and superseded in role by IPM1 Panther 2.[155]
• M88 ARV (Armored Recovery Vehicle): Armored recovery vehicle based on M60 chassis.
• Al-Monjed M60 ARV (Armored Recovery Vehicle): Jordanian M60 ARV variant. Starting in 1996, the King Abdullah II Design and Development Bureau (KADDB) began the conversion of 82 M60A1 RISE hulls into ARVs. The vehicle is based on the M60A1 RISE hull with an upgraded AVDS-1790-2DR engine. The turret has been replaced with a welded armored superstructure that provides protection from small arms and shell fragments. For recovery operations a turntable mounted hydraulically-operated crane fitted with a telescopic jib is mounted on the front right side of the chassis. Additionally a hydraulically-operated winch is located in the lower forward part of the chassis and leads out through the front of the vehicle. It has a front-mounted blade that can be used for vehicle stabilization or as a dozer blade.The vehicle is armed with a M2HB machine gun.[158]
• M728 Combat Engineer Vehicle: Combat Engineer Vehicle fitted with a folding A-frame crane and winch attached to the front of the turret, and an M135 165mm demolition gun mated to the M60 hull.
• M60CZ-10/25E Alacran: Spanish Army combat engineer variant. The main gun was replaced with a back hoe and is armed with a machine gun. Based on the M60A1 RISE hull.[159]

Additional equipment

• M9 Bulldozer Kit for the M60 series: (LIN B45390):[lower-alpha 3] The M9 bulldozer installed on the M60-series tank will increase the vehicle weight by 4.45 tons (4.04 metric tons). It is used to clear obstacles, leveling ground, filling depressions and to construct fighting positions. It is not to be used for demining activities. It is controlled by the driver.
• M1 Mine Clearing Roller System (MCRS) (LIN M18157): The MCRS is installed on the front of the tank through a removable adapter, and provides the capability for neutralization of Anti-Tank (AT) land mines, which are buried or laid on the surface, in the track path of the vehicle. The MCRS consists of two roller banks with two push arm assemblies. Each roller bank has four rollers, which apply ground pressure higher than that exerted by the tank. This principle ensures the explosion of pressure fused anti tank mines, which would otherwise explode under the track itself. Additionally a Magnetic Actuating Device (MAD) is connected between the two roller banks. The system weighs 10 short tons (9.07 metric tons).[131]
• Vehicle Magnetic Signature Duplicator (VEMSID): (LIN V53112) The VEMSID increases the effectiveness and survivability of countermine equipment by causing the stand-off detonation of magnetic influence mines at a safe distance ahead of the tank. It generates a multi-axial magnetic signature optimized for passively fused magnetic influence fused mines. The system comprises four emitter coils, two associated power boxes and a MSD Control Unit (MSDCU).[160]
• Pearson D7 Surface Mine Plow (SMP) (LIN B71620): It is a track-width plow designed to skim the surface of a flat roadway or trail, not to defeat buried mines. It is controlled by the driver.
• Track Width Mine Plow (TWMP) (LIN B71621): The Track Width Mine Plough (TWMP) uses a raking action to clear a safe path by bringing concealed or buried mines and improvised explosive devices (IEDs) to the surface and moving them wide and clear of the vehicle. It can be fitted with a MAD to counter magnetic influence fused mines.[161]

An M60A1 tank with a Track Width Mine Plow, Desert Storm February 1991

• Full Width Mine Rake (FWMR) (LIN B51986): A rake assembly for unearthing and disposing of buried and surface laid mines in sand and loose earth.[162] It was specifically designed and fabricated for use Operations Desert Shield and Desert Storm. It consists of a V-shaped tined plough that performs countermine activities by lifting buried mines with its tines and pushing them to the side as the vehicle moves forward. The FWMR also uses an aluminum skid shoe which protrudes from the front of the tines to allow the rake to maintain a consistent plowing depth.[163] It can be attached to any M728 CEV's D7 Surface Mine Plow or to a M60 series tank via a M9 Dozer Blade Assembly. It clears a path measuring 180 inches wide, accommodating heavy tanks and other armored vehicles. Additional features are that it weighs 4000 pounds and is easily assembled and installed.

• E60 series: Foreign Military Sales designation for the M60 series
  • E60: modified M60 variant for non-US service.
  • E60A: modified M60A1 variant for non-US service.
  • E60B: modified M60A3 variant for non-US service. Late conversion E60B tanks sold to Israel omitted the commander's cupola.[145]
• Iranian variants: All Iranian M60A1s were modified and given different local names.
  • Zulfiqar (the legendary sword of Ali): Iranian M60A1 variant. Armed with a Russian 2A46 125mm smoothbore main gun.[164]
  • 

    Turkish M60A1 tank upgraded by Israel Military Industries to M60T Sabra II, in Rishon LeZion, Israel, 2008
    Samsam (Sword): Iranian upgraded version of M60A1 tank, fitted with reactive armor (presumably Kontakt-5), EFCS-3 Fire Control system, Laser warning system and IR jammers.[165]
• Israeli variants: Many of the Israeli M60s have been upgraded with additional reactive or passive armor, drastically improving their armor protection. These up-armored versions are referred to as the Magach series.
  • Magach 6: Modernized M60/M60A1/M60A3. Fitted with the Urdan low profile cupola and Blazer ERA. Different configurations exist.
  • Magach 7: M60A1/A3 with 908 hp AVCR-1790-5A engine, additional passive armor, new fire control and Merkava-based tracks. Different configurations exist.
  • Pereh or Onager: an Israeli guided missile carrier, disguised as a tank. Based on the M60A1/A3 hull and Magach 7 component upgrades.
• Turkish variants: As a member of NATO, Turkey acquired a large fleet of M60A1 and A3 tanks. Many of them have been upgraded to the Sabra variant.
  • M60T Sabra Mk I: Turkish modernized M60A1/E60A variant with upgraded AVCR-1790 900 hp engine and suspension. Armed with M68T 105mm gun. Some retained the M19 cupola and were fitted with ERA packages and steel side skirts.[166]
  • M60T Sabra Mk II: Turkish M60A3/E60B upgrade of the Sabra M60MBT carried out in 2008. It features a MG251-LR 120mm main gun carrying 43 rounds, Elbit Knight fire control system, hybrid electrohydraulic turret drive, Orlite modular passive and ERA armor packages, SLAT armor for the turret, external armor plating to the hull front. Fitted with M19 style cupola. The power pack consisted of a 1,000 hp German RENK MTU 881 diesel engine coupled to a RENK 304S transmission and the same suspension and track assembly as the Merkava IV MBT.[166] Most upgraded to the Mk III configuration. Last 170 delivered in April 2010.[167]
  • M60T Sabra Mk III: same as the Mk II featuring improved modular armor. Cupola replaced with a Commanders Remote Operated Weapons System (CROWS).[166]
    • FIRAT-M60T or M60TM: Turkish local enhancement of the M60T Mk III Sabra main battle tank unveiled in 2019.[168] Fitted with a commander's independent thermal viewer (CITV), an RWR/IR warning system and with an active protection system.[166]
• Ramses II: Locally produced hybrid vehicle for the Egyptian Army, mating the T-55 turret to the M60A1 RISE hull.[169] Very few still in service.
• High Performance/Super M60: Teledyne Continental upgrade package for the M60A1/A3 offered in 1985. Features 105-mm M68A1 gun, new engine and suspension system, Chobham spaced applique armor for the turret, and other component improvements. One prototype built.
• M60-2000/120S: M60/Abrams hybrid vehicle developed by General Dynamics Land Division in 2001. One prototype built.
• M60 Phoenix: Jordanian upgrade, carried out in 2004 by the King Abdullah II Design And Development Bureau.[170] Upgrade features increased firepower (with a RUAG 120 mm smoothbore gun), IR jammers and modular armor protection scheme upgrade.
• Raytheon M60A3 SLEP: Raytheon modular update package for the M60A1/A3 first offered in 2016. Features RUAG 120-mm gun with autoloader, digital fire control system, STANAG level 6 armor plates for the hull, SLAT armor for the turret bustle, upgraded engine, and other component improvements.[171]
• RTA M60 MBT: Elbit Systems 2016 upgrade of the M60MBT for the Royal Thai Army. Upgrades for this package include upgraded AVDS-1790-2 engine, RENK304S transmission, new tracks and suspension systems. A 120mm MG253 cannon with M932 APAM (Anti-Personnel, Anti-Material) and LAHAT munitions, Iron Fist active protection system, new turret drives and Urdan cupola. Some have been fitted with a metal framework along the side of the vehicle filled with logs.[172]
  

  RTA M60A3 fitted with a steel side rack for holding logs
• Leonardo M60A3 SLEP: M60A3 SLEP modular upgrade package offered by Leonardo DRS in 2017.
• M60A3 Chariot: Taiwanese 2019 SLEP modular update of the M60A3 in conjunction with Elbit Systems.[173] Upgrades includes MG251/L44 120-mm gun with a semi-automatic load assist, Elbit Knight Independent Fire Control System (IFCS) with an independent thermal commander's sight, laser range finder, an RWR/IR warning system and Curtis-Wright electric turret drive. Improved hull suspension, improved NBC protection system and modular active and reactive armor packages.[174]

•  Afghanistan: 63 M60A3TTS were donated in 2009 from Greece to replace the ANA's aging Soviet era tanks. All are kept in reserve.[176]
•  Bosnia and Herzegovina: 45 M60A3s transferred from US in 1996 under Train and Equip Program[177] with all in service as of 2008.[178]
•  Bahrain: 180 M60A3 TTS excess US Forces Korea stocks. Last 54 were delivered in 1992 and as of 2014 60 were in service and the rest in reserve.[179]
•  Brazil: 91 M60A3s purchased from United States. 28 still in service as of 2012, others have been scrapped.[180]
•  Egypt: Purchased 1,600 M60A3s and 700 M60A1RISE from 1986 to 2002 from the United States and other countries. About half are in storage.[181]
•  Iran: 460 M60A1s were transferred from the US before 1979[182] with 150 in service as of 2010.[183] Many were given different names.
•  Israel: 111 Magach 7Cs in reserve storage.[184] Some M60A1 (Tagesh) AVLBs still in service. All M60/E60 series and Magach 6 series tanks retired in 2014 and to be scrapped or sold.[185] Superseded by the Merkava MBT.
•  Jordan: 82 M60A1s have been converted into Al-Monjed M60 Armored Recovery Vehicles. 240 M60A3TTS, former US Army National Guard, 182 were upgraded to M60 Phoenix.[186]
•  Lebanon: 56 M60A3s transferred from Jordan in 2008.[187] First 10 tanks received in May 2009 were rejected for service by Lebanese government.[188]
•  Morocco: 108 M60A1s transferred from US in 1981.[189] 300 former US Marine Corps M60A1s were purchased from 1991 to 1994, 120 M60A3TTS and 7 M60A1 in 1997. M60A1 tanks purchased in the 1990s were upgraded to A3s and 140 upgraded to M60A3TTS in 2009.[190] As of 2015 they were still in service.
•  Oman: 93 M60A3s Last 39 acquired in 1990 from inventories at Fort Knox.[5] As of 2015 they are still in service.
•  Saudi Arabia: 910 M60A1RISE (250 transferred to North Yemen).[129] Many of these were upgraded to M60A3s during the 1990s.[191] 390 M60A3s purchased in 1990.[5]
•  Spain: 400 M60A3TTSs received in 1991 and 1992 from Conventional Forces in Europe (CFE) Treaty. Some transferred to Greece, others scrapped. Superseded by the Leopard 2.As of 2020, there are 34 M60CZ-10/25E engineer vehicles, 12 M60VLPD-26/70E bridge layers and 4 M60 AVLB bridge layers in service with the Spanish Army.[159]
•  Sudan: 20 M60A1s received in 1979 from United States. They remain in service as of 2014.[192][193]
•  Taiwan: 400 M60A3TTS and 400 CM-11 Brave Tiger in service as of 2018.[194]
•  Thailand: 53 M60A1RISE Passive and 125 M60A3TTS from US Army. Still in service as of 2015.[195]
•  Tunisia: 59 M60A3 TTS and 30 M60A1 RISE Passive received from the US in 1985. As of 2012 they are still in service.[196]
•  Turkey: Received 104 M60A1 RISE Passive and 658 M60A3TTS. 170 were converted to M60T Sabra II. As of 2018 170 M60T, 610 M60A3TTS and 752 M60A3 in service.[197]
•  United States: As of 2015 QM60s are in limited use as target vehicles for weapons and radar testing. The M60 series was retired from combat use in 1991, the Army National Guard in 1997, and as a training aid in 2005. The M728 Combat Engineer Vehicle was retired from combat use in 2000. 262 M728s in service with the US Army Reserve and Army National Guard[198] as of 2007. Phased replacement with the M1150 Assault Breacher Vehicle starting 2018.[199] 37 M60 AVLB vehicles in service with US Marine Corps as of 2009.[200] To be replaced with the M1074 Joint Assault Bridge starting in 2019.[201]
•  Yemen: 250 M60A1 RISE Passive in 1990. As of 2015 approx. 50 were still in service[202]

•  Argentina: One M60A1 acquired in the early 1970s from United States. Never placed in service. As of March 2014 it is displayed as a monument in the Army NCOs School, in Campo de Mayo, outside Buenos Aires.[203]
•  Austria: 170 M60A1s purchased from USAEUR excesses 1982. Later converted to A3 standard. They were replaced in 1997 by the Leopard 2 and sold to Egypt.[204]
• Ethiopia: 180 M60A1s received from the US from 1974 to 1977. Replaced with the T-72 in 1978 and 1979.[205]
•  Greece: 357 M60A1RISE and 312 M60A3TTS were received under the Conventional Forces in Europe (CFE) Treaty in 1991 and 1992.[206] 63 donated to Afghanistan in 2009. Retired from service 2015 and remaining M60s to be scrapped.[41]
•  Iraq: Limited ad hoc use of Iranian tanks during Iran–Iraq War.[207] Six Iranian M60A1s were captured in 1980 and transferred to Jordan.[208] Any remaining tanks were destroyed after the war. It was never officially in Iraqi service.
•  Italy: 200 M60A1s produced in Italy and 100 from excess USAEUR stocks in the late 1970s. Phased out of service by 2008.[209]
•  Portugal: 96 M60A3 tanks from redundant US Army inventory in Europe in 1991 and 1992 as a result of the CFE Treaty. Were formally phased out in 2018 and replaced by the Leopard 2 A6.[210]

• AMX-30: French main battle tank
• Chieftain: British main battle tank
• Leopard 1: German main battle tank
• Stridsvagn 103: Swedish turret-less main battle tank
• T-62: Soviet main battle tank
• T-64: Soviet main battle tank
• T-72: Soviet main battle tank
• TR-85: Romanian main battle tank
• Type 69/79: Chinese main battle tank
• Type 74: Japanese main battle tank
• Vijayanta: Indian main battle tank