The venerable M60 was standardized in March 1959 by the US
Army, and entered production as the world’s first purpose-designed production
Main Battle Tank. Some will argue that the Centurion, which was the first to
carry the L7 105mm gun, could hold the title of the first Main Battle Tank, but
it was initially designed as a cruiser tank, became a Medium Gun Tank when the
20-pdr was developed, and subsequently most were retrofitted with the 105mm gun
to become Main Battle Tanks, often five to ten years after manufacture. The M60
series were expected to serve the Main Battle Tank role right off the drawing
board.
Over 15,000 M60 series Main Battle Tanks were produced and
the type went on to serve the USA into the 1990s. It beat the Chieftain,
Leopard and AMX30 into service by five or six years and it continues in use in
many armies right up to the present day. It bore the classic features of a
lineage that stretched back to the M26 of 1944: a powerful main armament, heavy
armour and good mobility.
The M60 earned its reputation as an effective family of
combat tanks that bested the T55 and T62 in most encounters during the 1973 Yom
Kippur war. This war made Continental Europe’s tank designers re-examine their
design priorities and confirmed the importance of protection and firepower in
American tank design. Its gun proved effective against any opponent it was
called upon to fight. The M60’s excellent powertrain proved adaptable and was
widely adopted in Israeli designs to improve tanks like the Centurion and to
power their own Merkava.
The M60 program also yielded many improvements that were
then applied to the M48A3 and M48A5 to keep older vehicles in service for
decades. By any measure, the M60 was a successful tank design, one of the
finest of the Cold War era, but one seldom recognised for its overall
excellence.
The T95, the T60, and M60.
In the mid-1950s the United States Army was developing a
lighter, more powerfully armed, more mobile and better armoured successor to
the M48, itself a newly standardised medium tank. This was the T95, a visionary
design with tremendous potential, and one that incorporated a great deal of new
technology. The T60 was a modernisation of the M48A2, developed from a United
States Army requirement for a lower risk medium weight tank alternative to the
T95 program and was instituted in mid-1957. The objective of the T60 program
was to bring a universal or Main Battle Tank into service with significant
improvements over the existing M48A2 within a short time and employing
available technology (and M48 derived components) wherever possible. The Main
Battle Tank concept was intended to replace the M48 Medium Tank and M103 Heavy
Tank with one heavily armed, highly mobile battle tank in the 40 to 55-ton
range. The T60 was not originally expected to supersede the T95 program, but
rather to supplement the existing M48 fleet as a advanced T95 was still
expected to be produced and brought into service in the early 1960s.
The fundamental advantages enjoyed by the T95 over the M48A2
lay in its use of a diesel engine and in its superior fire power. The Army
Bureau of Budget saw the M48 series as costly to operate and in need of
modernisation or replacement as soon as possible. The quickest means of
improving the situation was to replace the M48A2’s gasoline engine with a
related Continental product, the AVDS-1790-2, which was simple to place in
production and was a relatively mature design. The 750 HP engine was mated to
an effective transmission, the CD-850-6, which gave the vehicle far better fuel
economy than the M48A2 and a range of nearly 500km.
In 1958 the decision was taken to develop an American
version of the Royal Ordnance L7 105mm gun, which became the T254. The British
105mm gun had been developed during the 1956-57 scare caused by the inspection
of a T54 on the British embassy grounds in Budapest during the Soviet
intervention in 1956. It had been achieved by the simplest of means-by
increasing the bore of their existing QF 20-Pounder, an 83.4mm gun of similar
dimensions to the M48’s US 90 mm M41 gun. The T254 was adopted as the M68 after
extensive testing by the US Army in 1958, and the M116 gun mounting was adapted
to the M48A2 turret casting. The M48A2C was still in production at the time and
extensive testing was accomplished on modified M48A2s to develop the new tank.
This choice of gun simplified the T60’s development considerably (although many
changes to the M48A2 turret to suit the T60 were required, including a larger
cupola ring).
Like the M48 series the T60 would employ an enclosed
commander’s cupola, albeit one much larger than the M1 cupola fitted from the
M48A1 onwards- a feature that production M60s retained right up to retirement
from American service in the 1990s. The T60 turret’s frontal armour (as per the
M48A2C) was a maximum of 180mm thick and 54 105mm rounds could be short- term
solution to getting an effective counter to the Soviet T54 into service. At the
time the T60 program started, the more carried for the main armament.
The T60’s cast hull was also based on the general layout
employed on the M48A2, with some significant alterations. The most noticeable
feature was the adoption of a flat glacis slope, compared to the rounded hull
front seen on tanks like the M103 and M48 series. The T60’s hull’s frontal
armour layout was roughly 100mm thick, and to save weight aluminium was used
extensively for the road wheels. The driver, located in the middle of the front
of the hull, enjoyed the same ease driving the T60 as its predecessor the M48.
A floor escape hatch was provided immediately behind his seat.
The T60 was intended to be able to move and fight at night
and was built with night driving in mind right from the start. The driver was
provided with three periscopes, the middle of which could be replaced with a
M24 infrared vision device. It carried a large Xenon light projector on the gun
mantlet in a similar installation to the Crouse Hinds searchlight carried on
the M48A2 and infrared sights were provided for the gunner and commander.
The T60 designation was changed to XM60 during the last
months of 1958, and was standardised as the M60 in March 1959. It was ordered
into production by the end of the year, carrying the Patton nickname used on
the M47 and M48 forward, but was never officially to bear that name. The first 360
M60s were built in Delaware at the Chrysler Newark plant, and nearly 1700 more
were manufactured at the Detroit Tank Plant.
M60A1
The first M60s entered service at the end of 1960. With the
M60 in production, the next two years were spent adapting the best features of
the T95’s turret to the M60 design, which resulted in the M60A1, first produced
in mid-1962. An estimated 12,000 M60A1s were built and the type remained in
production for about two decades (the monthly deliveries increasing after 1973
in response to the need to have a reserve of vehicles in case of crisis or
war). The new turret had a maximum frontal armour thickness of 250mm, and was
longer, with more crew space. There was increased stowage for 58 rounds of
105mm ammunition. The M60A1 introduced a 120mm thick glacis, an improved
powertrain, improved crew positions and an improved suspension. Last of all,
the M60A1 introduced new fire controls and improved combination (day and
infrared) sights for the commander and gunner. This was the definitive version
of the M60 family, which retained the optical rangefinder system of the M60 in
improved form, but it still lacked an effective gun stabilisation system.
At around the same time that the M60 entered production, the
T95 program was sidelined and eventually cancelled. The M60’s introduction also
speeded the M103 heavy tank into retirement, except in the United States Marine
Corps (where it was adopted with the significant substitution of the M60’s
AVDS-1790 engine and cross-drive transmission). The M48A3 was largely improved
as a result of the M60’s component and drivetrain development. It was improved
subsequently in the 1970s into the M48A5 as the M60A1 underwent
modernisations.
The adoption of the L7 gun in the UK and its modification
for American use as the M68 was a fundamentally important event, because it
caused nearly every army that benefitted from American generosity in ammunition
production to adopt compatible L7 or M68 based weapons either produced by the
British, in the USA or under license from either nation. This influenced the
adoption of this type of 105mm gun across nearly all the NATO nations for tanks
introduced in the 1960s (with the exception of the French, although the British
ironically retired their 105mm armed Centurions between 1967 and 1972 in favour
of the Chieftain armed with an L11 120mm rifled gun). The M60 series was
adopted in Italy, Israel, Spain, Greece, Turkey and many other friendly
nations. The 1970s saw many incremental improvements added during the M60A1
production run and to vehicles which were rebuilt. The most significant came in
1972, a gun stabilisation system to give the M60A1 a fire on the move
capability at long last. Besides the add-on gun stabiliser other improvements
included new tracks and top-loading air cleaners.
M60A2
The M60A2 was the problem child of the M60 family, with an
exceptionally long development time complicated by the fact that its main
armament was beset with teething problems. The T95 was succeeded in the US
developmental pipeline by the MBT70 concept and here American-West German
co-production and co- development proved extremely difficult to coordinate. The
MBT70 pursued between 1963 and 1971 was based on innovative, high risk
technology and the armament system chosen to arm the American version spilled
over into both the air-transportable tank concept (M551)and into the M60
program.
The Ford MGM51 Shillelagh Guided Missile Gun system chosen
to arm the US MBT70 was adapted to a special turret designed to be mounted on a
standard M60A1 hull in 1964 as the M60A1E1. The MGM51 employed an infrared
guidance system, which proved difficult to perfect and difficult to adapt to an
MBT fire control system. It also had tactical limitations in an armoured
battle. The Shillelagh missile was a weapon that required line of sight control
throughout its flight onto its target, which required the gunner’s full
concentration at the expense of any sudden threat or any subsequent target
acquisition. Other problems were encountered in the combustion of the 152mm
conventional round’s cases intended for use when not engaging enemy MBT
targets. The cost of the war in Vietnam impacted many weapon systems in the
late 1960s. It also highlighted many problems with the 152mm/ Shillelagh system
deployed with the M551s. The system’s reputation was sullied- and missile
launching tanks came to be viewed with derision by armored corps officers as
technical problems piled up. Full resolution of the issues associated with the
Shillelagh were never achieved to a satisfactory level.
The Shillelagh-armed version of the M60 was tested over the
course of several years and was ordered in 1971 (at around the same time that
the MBT70 was cancelled). The turrets had been approved for production and paid
for in 1966 and the hulls the following year, so it is unclear if the M60A2s
were assembled from 243 existing stored turrets and hulls in 1971 or built from
scratch. The M60A2 was a complex vehicle but it was eventually made to work.
The Shillelagh missile, if successfully guided to its target, could defeat any
tank of its generation, and the system could fire a range of powerful 152mm low
velocity rounds when operating in the gun role. Additionally, the M60A2
suffered from a low rate of fire due to the need to purge the gun after each conventional
round or the need to remove an obturator plate after each missile was fired. A
standard stowage included 13 missiles and 33 rounds of 152mm ammunition of up
to three different types.
Overshadowed by advances in gun development in the mid-1970s
and by the success of simpler antitank missile systems like the TOW, the M60A2
was withdrawn from service in 1980. It only served in armored regiments for
about six years, and it disappeared as soon as the M1 came on line in quantity
in 1980. Its crews remember it as a vehicle that absorbed many man hours in
maintenance, trouble shooting training and system checks to keep operational.
Next to the new M1 Abrams, it might have seemed that the guided missile MBT was
a technological dead end. Nearly all of the M60A2s were remanufactured and put
to good use after retirement, some becoming bridgelayers, and others becoming
M60A3s.
M60A1 RISE
The M60 and M60A1 were adopted throughout the United States
Army’s armoured divisions in the early 1960s, and the M48 was supplemented and
gradually replaced, except in the USMC and in Army armored units outside of
Europe. It saw no action in the Viet Nam conflict, but was instead blooded
against some of the best weapons the Soviets had developed in the 1973 Yom
Kippur War in Israeli service. The M60A1 underwent a major upgrades from 1975
and 1977 onwards to improve key features, under the acronym RISE (Reliability
Improved Selected Equipment). The original RISE program
was oriented towards the improvement of the powertrain, introducing the
AVDS-1790- 2C engine and improvements to the electrical system. The program was
expanded in 1977 to improve turret systems, introducing passive night vision
sights for the gunner and commander and new passive driving optics for the
driver (these tanks being designated M60A1 RISE PASSIVE). The M60A1 RISE
PASSIVE also introduced a fording kit to rival those in use in the Leopard 1
and the AMX30, which allowed the M60A1 to perform river crossings completely
submerged.
M60A3
The last production version of the M60 gun tank was
introduced in 1978, as the M60A3. This vehicle incorporated fire controls based
on new ballistic computer and a new laser rangefinder. These were linked to a
new gun stabiliser. The M60A3 thus brought the basic M60A1 configuration up to
date for the 1980s, a decade where the arrival of new tanks like the M1,
Leopard II and Challenger introduced advances like Chobham armour, hunter
killer fire controls and 120mm main armaments. If the M60A3 was overshadowed by
the technological marvel that the M1 represented, it honorably held the line
with the M60A1 while enough M1s were built. When the Cold War ended the M60A1
and M60A3 disappeared rapidly from the US inventory. Some 5000 M60A1s were
remanufactured as M60A3s by that time and the type was very well regarded by
its crews.
Conclusion
Over the years some have derided the M60 series because the
M68 gun wasn’t quite as powerful as the Chieftain’s L11 120mm, or because it
wasn’t as agile as the Leopard or AMX30. It has been criticized for its high
silhouette and for its 51- ton weight in some quarters. It cannot be argued
that it proved to be a fine combat vehicle and one that earned its spurs the
hard way-on the battlefield. The M60
continues to defy its detractors and is still in service in many countries.
Modern upgrades for the venerable M60A1 and M60A3 range from 120mm main
armament kits to extensive passive and active armour upgrades, as well as a
whole range of improved optics and fire controls in keeping with modern
electronic advances. As such, the M60 soldiers on, a remarkable feat of
longevity and a tribute to its sound design.
