MGM-51 Shillelagh
Encyclopedia
The Ford
MGM-51 Shillelagh was an American anti-tank guided missile
designed to be launched from a conventional gun
(cannon). It was originally intended to be the medium-range portion of a short, medium, long-range system for armored fighting vehicles in the 1960s and '70s to defeat future armor without an excessively large gun. Developing a system that could fire both shells and missiles reliably proved complex and largely unworkable. It served most notably as a primary weapon of the M551 Sheridan
light tank, but the missile system was deleted from units serving in Vietnam. Ultimately very few of the 88,000 rounds produced were ever fired in combat.
The Shillelagh was a disappointment compared to the later BGM-71 TOW
anti-tank guided missile first produced in 1970 by the U.S. The TOW system, which could not fire gun rounds, and was guided by a wire which directly sent commands to the missile, proved simpler and more versatile. TOW became the most widely used anti-tank guided missile in the world based on a range of light, armoured and flying vehicles. Main battle tanks of the late 20th century such as the successful M1 Abrams
tank fielded improved conventional 105mm and 120mm guns which proved effective against enemy armor threats. While the Russians are developing gun launched missiles, the US and NATO are developing guided tank shells.
The name comes from a type of wooden club associated with Ireland
.
, tanks were becoming increasingly able to survive rounds fired from even the largest of WWII-era anti-tank guns. A new generation of guns, notably the British
105 mm Royal Ordnance L7
, were able to cope with newer tanks, but it appeared that in another generation the guns needed would be too large to be practical.
Instead the US Army started concentrating on HEAT
rounds in the 1950s. HEAT penetration is not dependent on the speed of the round, allowing it to be fired at much lower velocities, and thus from a much lighter gun. They also work better at larger diameters, and a large-diameter low-velocity gun makes for an excellent assault gun
vehicle. On the downside, the low speed also means that they become increasingly hard to aim over longer distances. The US Army looked to address this problem with the use of HEAT-equipped guided missile
s for anything beyond a few hundred yards.
and Ford Aeronutronic
were asked for designs to fill the shorter range role. Ford won the contract and started work on the XM13. The first test shots occurred in 1960, and limited production started in 1964, now known as the MGM-51A.
The basic system was quite advanced for its day. The missile body consisted of a long tube with fold-out fins at the extreme rear, which was propelled from the new M81 gun with a small charge strapped on the rear. Once clear of the gun the fins popped open and the engine ignited. In order to keep it from spinning while in the gun due to the rifling, a small "key" fit into a straight groove in the rifled gun. Aiming the missile was simple; the gunner simply kept his gunsight on the target, while electronics in the sighting system tracked the missile optically and sent corrections through an IR
link (similar to a TV remote control). In general the gunners were able to achieve excellent hit ratios with the system.
Because the system was so advanced, the development of the Shillelagh was fraught with problems. Ford Aeronutronic underestimated the complexity of the task of designing a missile this advanced, and there were major problems with the propellant, igniter, tracker and infrared command link of the missile.
The M81/MGM-51 was first installed on the M551 Sheridan
, which appeared at first to prove the value of the system. The Sheridan was a light aluminum-armored AFV designed to be air transportable and provide antitank support for airborne forces
. In 1966 the US Army began pressing General Westmoreland to field the tank in South Vietnam
, but he declined, stating that with no main gun ammunition, the Sheridan was basically nothing more than a $300,000 machine gun platform. In 1968 152mm main gun ammo became available, and the M551 General Sheridan was deployed to South Vietnam for combat operations in January 1969. Shillelagh missiles did not prove to be a problem in the Vietnam War
; they weren't used.
During combat operations in Vietnam the Sheridan's 152mm main guns proved operational, but during their first deployment in country were a cause of persistent trouble. The 152mm caseless ammunition
rounds were themselves troublesome because the casings did not burn completely, requiring a complicated and slow gas-driven scavenging system. They were also liable to cook off if the vehicle were hit. Firing the gun caused such a large recoil as to result in failures in the delicate missile firing electronics on the tank. These problems, followed by the lack of suitable targets, resulted in the Sheridan's deployment to South Vietnam without the complex missile system.
The Shillelagh was considerably larger than a conventional round, so only a small number could be carried. Typical loads consisted of only 8 missiles and twenty M409 HEAT rounds for short-range use. In addition the missile proved to have a very long minimum range due to the layout of the vehicle, the missile didn't come into the sight of the gun/tracker system until it was 800 yards (731.5 m) from the vehicle, at which point it could start to be guided. Because of its maximum range of about 2200 yards (2,011.7 m), the system was left with a fairly large "dead zone".
While the maximum range of 2200 yards (2,011.7 m) was usable, the Army felt it could use improvement. Ford received a contract to study a longer range version in 1963, and returned a slightly larger design the next year. Test shots of the new MGM-51B started the next May, and production in October 1966. Only one other change was made to the system. In testing it was found that the key slot in the gun led to cracking after firing only a few shells. After further study a version with a shallower slot and new barrel was selected, creating the M81E1/MGM-51C. The missile was about 45 inches (114.3 cm) long, about 6 inches (15.2 cm) in diameter, and weighed 60 pounds (27.2 kg). It remained in production until 1971, by which time 88,000 had been produced, probably in anticipation of use by main battle tanks (below). Nearly a half dozen missiles fired at bunkers by Sheridans during Operation Desert Storm (Iraq/Kuwait) in January and February 1991 was the only time the missile system was fired in a combat environment.
Even with these problems the system clearly proved it could be used by an airborne tank to destroy a main battle tank. The question of whether or not it could fill its original role as the main armament of all tanks was still open. The Army had originally started development of a low-profile turret with a short barrel for their existing M60
tanks in the 1960s, but didn't contract for actual delivery until 1971 once the bugs had been worked out. They entered service in 1974, but were hampered by reliability problems, and soon phased out in 1980. The final revision of the M60A3 used the same gun and turret as the M60A1.
The most ambitious project based on the system was the MBT-70
, an advanced US-German
tank design that started in 1963. It mounted a huge auto-loader turret on top of a very short chassis, so short that there was no room for a driver. Instead he was relocated into the turret with everyone else, in a rotating cupola that kept him facing forward. The gun was a new longer-barreled design, the XM-150, which extended range and performance to the point where it was useful for sabot
type rounds as well. However the project dragged on, and in 1969 the estimated unit cost had risen 5 times, and Germany pulled out of the effort. The Army proposed a "cut-down" version of the system, but Congress cancelled it in November 1971. It started the M1 Abrams
project with its funds the next month, which used a conventional gun.
The Soviet KBP Instrument Design Bureau developed the somewhat similar AT-11 Sniper
, launched by a 125 mm gun system. It utilizes a Laser Beam Rider guidance system, and a tandem warhead to defeat vehicles fitted with Explosive Reactive Armour as used on the T-80/90 Tanks.
Aeronutronic
Aeronutronic was a defense and space related division of Ford Motor Company set up in 1956. In 1961 Ford purchased Philco and merged the two companies in 1963. Aeronutronic provided major support for the development of Project Space Track...
MGM-51 Shillelagh was an American anti-tank guided missile
Anti-tank guided missile
An anti-tank missile , anti-tank guided missile , anti-tank guided weapon or anti-armor guided weapon is a guided missile primarily designed to hit and destroy heavily-armored military vehicles....
designed to be launched from a conventional gun
Gun
A gun is a muzzle or breech-loaded projectile-firing weapon. There are various definitions depending on the nation and branch of service. A "gun" may be distinguished from other firearms in being a crew-served weapon such as a howitzer or mortar, as opposed to a small arm like a rifle or pistol,...
(cannon). It was originally intended to be the medium-range portion of a short, medium, long-range system for armored fighting vehicles in the 1960s and '70s to defeat future armor without an excessively large gun. Developing a system that could fire both shells and missiles reliably proved complex and largely unworkable. It served most notably as a primary weapon of the M551 Sheridan
M551 Sheridan
The M551 Sheridan was a light tank developed by the United States and named after Civil War General Philip Sheridan. It was designed to be landed by parachute and to swim across rivers. It was armed with the technically advanced but troublesome M81/M81E1 152mm gun/launcher which fired conventional...
light tank, but the missile system was deleted from units serving in Vietnam. Ultimately very few of the 88,000 rounds produced were ever fired in combat.
The Shillelagh was a disappointment compared to the later BGM-71 TOW
BGM-71 TOW
The BGM-71 TOW is an anti-tank missile. "BGM" is a weapon classification that stands for "Multiple Environment , Surface-Attack , Missile ". "TOW" is an acronym that stands for "Tube-launched, Optically-tracked, Wire command data link, guided missile"...
anti-tank guided missile first produced in 1970 by the U.S. The TOW system, which could not fire gun rounds, and was guided by a wire which directly sent commands to the missile, proved simpler and more versatile. TOW became the most widely used anti-tank guided missile in the world based on a range of light, armoured and flying vehicles. Main battle tanks of the late 20th century such as the successful M1 Abrams
M1 Abrams
The M1 Abrams is a third-generation main battle tank produced in the United States. It is named after General Creighton Abrams, former Army Chief of Staff and Commander of US military forces in Vietnam from 1968 to 1972. The M1 is a well armed, heavily armored, and highly mobile tank designed for...
tank fielded improved conventional 105mm and 120mm guns which proved effective against enemy armor threats. While the Russians are developing gun launched missiles, the US and NATO are developing guided tank shells.
The name comes from a type of wooden club associated with Ireland
Ireland
Ireland is an island to the northwest of continental Europe. It is the third-largest island in Europe and the twentieth-largest island on Earth...
.
Background
With the rapid increase in armor during World War IIWorld War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...
, tanks were becoming increasingly able to survive rounds fired from even the largest of WWII-era anti-tank guns. A new generation of guns, notably the British
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...
105 mm Royal Ordnance L7
Royal Ordnance L7
The Royal Ordnance L7 is the basic model of Britain's most successful tank gun. The L7 was a 105 mm L/52 rifled design intended for use in armoured fighting vehicles...
, were able to cope with newer tanks, but it appeared that in another generation the guns needed would be too large to be practical.
Instead the US Army started concentrating on HEAT
Heat
In physics and thermodynamics, heat is energy transferred from one body, region, or thermodynamic system to another due to thermal contact or thermal radiation when the systems are at different temperatures. It is often described as one of the fundamental processes of energy transfer between...
rounds in the 1950s. HEAT penetration is not dependent on the speed of the round, allowing it to be fired at much lower velocities, and thus from a much lighter gun. They also work better at larger diameters, and a large-diameter low-velocity gun makes for an excellent assault gun
Assault gun
An assault gun is a gun or howitzer mounted on a motor vehicle or armored chassis, designed for use in the direct fire role in support of infantry when attacking other infantry or fortified positions....
vehicle. On the downside, the low speed also means that they become increasingly hard to aim over longer distances. The US Army looked to address this problem with the use of HEAT-equipped guided missile
Guided Missile
Guided Missile is a London based independent record label set up by Paul Kearney in 1994.Guided Missile has always focused on 'the underground', preferring to put out a steady flow of releases and developing the numerous GM events around London and beyond....
s for anything beyond a few hundred yards.
Development
In 1958 they felt the state of the art had progressed enough to start work on such designs, and in June 1959 SperrySperry
-Persons:*Armstrong Sperry , American author and illustrator*Brett Sperry , American video game designer*Carlos A. Sperry, Democratic President of the West Virginia Senate from Greenbrier County, served 1872-1872...
and Ford Aeronutronic
Aeronutronic
Aeronutronic was a defense and space related division of Ford Motor Company set up in 1956. In 1961 Ford purchased Philco and merged the two companies in 1963. Aeronutronic provided major support for the development of Project Space Track...
were asked for designs to fill the shorter range role. Ford won the contract and started work on the XM13. The first test shots occurred in 1960, and limited production started in 1964, now known as the MGM-51A.
The basic system was quite advanced for its day. The missile body consisted of a long tube with fold-out fins at the extreme rear, which was propelled from the new M81 gun with a small charge strapped on the rear. Once clear of the gun the fins popped open and the engine ignited. In order to keep it from spinning while in the gun due to the rifling, a small "key" fit into a straight groove in the rifled gun. Aiming the missile was simple; the gunner simply kept his gunsight on the target, while electronics in the sighting system tracked the missile optically and sent corrections through an IR
Infrared
Infrared light is electromagnetic radiation with a wavelength longer than that of visible light, measured from the nominal edge of visible red light at 0.74 micrometres , and extending conventionally to 300 µm...
link (similar to a TV remote control). In general the gunners were able to achieve excellent hit ratios with the system.
Because the system was so advanced, the development of the Shillelagh was fraught with problems. Ford Aeronutronic underestimated the complexity of the task of designing a missile this advanced, and there were major problems with the propellant, igniter, tracker and infrared command link of the missile.
The Sheridan
M551 Sheridan
The M551 Sheridan was a light tank developed by the United States and named after Civil War General Philip Sheridan. It was designed to be landed by parachute and to swim across rivers. It was armed with the technically advanced but troublesome M81/M81E1 152mm gun/launcher which fired conventional...
, which appeared at first to prove the value of the system. The Sheridan was a light aluminum-armored AFV designed to be air transportable and provide antitank support for airborne forces
Airborne forces
Airborne forces are military units, usually light infantry, set up to be moved by aircraft and 'dropped' into battle. Thus they can be placed behind enemy lines, and have an ability to deploy almost anywhere with little warning...
. In 1966 the US Army began pressing General Westmoreland to field the tank in South Vietnam
South Vietnam
South Vietnam was a state which governed southern Vietnam until 1975. It received international recognition in 1950 as the "State of Vietnam" and later as the "Republic of Vietnam" . Its capital was Saigon...
, but he declined, stating that with no main gun ammunition, the Sheridan was basically nothing more than a $300,000 machine gun platform. In 1968 152mm main gun ammo became available, and the M551 General Sheridan was deployed to South Vietnam for combat operations in January 1969. Shillelagh missiles did not prove to be a problem in the Vietnam War
Vietnam War
The Vietnam War was a Cold War-era military conflict that occurred in Vietnam, Laos, and Cambodia from 1 November 1955 to the fall of Saigon on 30 April 1975. This war followed the First Indochina War and was fought between North Vietnam, supported by its communist allies, and the government of...
; they weren't used.
During combat operations in Vietnam the Sheridan's 152mm main guns proved operational, but during their first deployment in country were a cause of persistent trouble. The 152mm caseless ammunition
Caseless ammunition
Caseless ammunition is a type of small arms ammunition that eliminates the cartridge case that typically holds the primer, propellant, and projectile together as a unit...
rounds were themselves troublesome because the casings did not burn completely, requiring a complicated and slow gas-driven scavenging system. They were also liable to cook off if the vehicle were hit. Firing the gun caused such a large recoil as to result in failures in the delicate missile firing electronics on the tank. These problems, followed by the lack of suitable targets, resulted in the Sheridan's deployment to South Vietnam without the complex missile system.
The Shillelagh was considerably larger than a conventional round, so only a small number could be carried. Typical loads consisted of only 8 missiles and twenty M409 HEAT rounds for short-range use. In addition the missile proved to have a very long minimum range due to the layout of the vehicle, the missile didn't come into the sight of the gun/tracker system until it was 800 yards (731.5 m) from the vehicle, at which point it could start to be guided. Because of its maximum range of about 2200 yards (2,011.7 m), the system was left with a fairly large "dead zone".
While the maximum range of 2200 yards (2,011.7 m) was usable, the Army felt it could use improvement. Ford received a contract to study a longer range version in 1963, and returned a slightly larger design the next year. Test shots of the new MGM-51B started the next May, and production in October 1966. Only one other change was made to the system. In testing it was found that the key slot in the gun led to cracking after firing only a few shells. After further study a version with a shallower slot and new barrel was selected, creating the M81E1/MGM-51C. The missile was about 45 inches (114.3 cm) long, about 6 inches (15.2 cm) in diameter, and weighed 60 pounds (27.2 kg). It remained in production until 1971, by which time 88,000 had been produced, probably in anticipation of use by main battle tanks (below). Nearly a half dozen missiles fired at bunkers by Sheridans during Operation Desert Storm (Iraq/Kuwait) in January and February 1991 was the only time the missile system was fired in a combat environment.
M60 "Starship"
M60 Patton
The 105 mm Gun Full Tracked Combat Tank, M60, also known unofficially as the M60 Patton, is a first-generation main battle tank introduced in December 1960. It was widely used by the U.S. and its Cold War allies, especially those in NATO, and remains in service throughout the world today...
tanks in the 1960s, but didn't contract for actual delivery until 1971 once the bugs had been worked out. They entered service in 1974, but were hampered by reliability problems, and soon phased out in 1980. The final revision of the M60A3 used the same gun and turret as the M60A1.
MBT-70
MBT-70
The MBT-70 was a 1960s German-U.S. joint project to develop a new main battle tank, which was to be equipped with a number of advanced features. It utilized a newly developed hydropneumatic "kneeling" suspension and housed the entire crew in the large turret...
, an advanced US-German
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...
tank design that started in 1963. It mounted a huge auto-loader turret on top of a very short chassis, so short that there was no room for a driver. Instead he was relocated into the turret with everyone else, in a rotating cupola that kept him facing forward. The gun was a new longer-barreled design, the XM-150, which extended range and performance to the point where it was useful for sabot
Sabot
A sabot is a device used in a firearm or cannon to fire a projectile, such as a bullet, that is smaller than the bore diameter, or which must be held in a precise position. The term is also applied to a battery stub case, a device used similarly to make a small electrical battery usable in a...
type rounds as well. However the project dragged on, and in 1969 the estimated unit cost had risen 5 times, and Germany pulled out of the effort. The Army proposed a "cut-down" version of the system, but Congress cancelled it in November 1971. It started the M1 Abrams
M1 Abrams
The M1 Abrams is a third-generation main battle tank produced in the United States. It is named after General Creighton Abrams, former Army Chief of Staff and Commander of US military forces in Vietnam from 1968 to 1972. The M1 is a well armed, heavily armored, and highly mobile tank designed for...
project with its funds the next month, which used a conventional gun.
The Soviet KBP Instrument Design Bureau developed the somewhat similar AT-11 Sniper
AT-11 Sniper
The 9M119 Svir and 9M119M Refleks are laser beam riding, guided anti-tank missiles developed in the former Soviet Union. The two missiles are similar, but vary in range and launch platform. Both are designed to be fired from smooth bore 125 mm tank and anti-tank gun . Their NATO reporting name...
, launched by a 125 mm gun system. It utilizes a Laser Beam Rider guidance system, and a tandem warhead to defeat vehicles fitted with Explosive Reactive Armour as used on the T-80/90 Tanks.