Replies

Ford M13/MGM-51 Shillelagh

The MGM-51 Shillelagh was the first gun-launched guided missile deployed by the U.S. Army ground forces.

Shillelagh missiles

In the 1950s, the U.S. Army looked for improved anti-armour weapon systems for the modern battlefield, and in 1958, the Combat Vehicle Weapon System program was approved. This program called for the development of new fighting vehicles, as well as guided missile type anti-tank weapons for short and medium ranges. For the short-range missile, Sperry and Ford Aeronutronics submitted design proposals, and in June 1959, Ford received a development contract for their system. The Ford missile was designated as Guided Missile, Armour Defeating, XM13, and named Shillelagh. The first launch of a Shillelagh prototype occurred in November 1960, and the test shots of guided rounds began in September 1961. In June 1963, the XM13 Shillelagh was redesignated as XMGM-51A, and in 1964 limited production of the XMGM-51A, together with the XMTM-51A training rounds, began. In May 1966, the Shillelagh was designated as standard equipment, and the tactical and training rounds were redesignated as MGM-51A and MTM-51A, respectively. In January 1967, the MGM-51A was first fielded by operational U.S. Army units.

This is an artist's concept of the Shillelagh weapon system developed for the US Army.

The primary deployment vehicle for the Shillelagh missile was the M551 Sheridan AFV (Armoured Fighting Vehicle), which could also fire conventional unguided M409 HEAT (High-Explosive Anti-Tank) rounds from its M81 gun. A typical loadout consisted of 8 Shillelagh missiles and 20 M409 rounds. In a Shillelagh shot, the gunner aimed the cross-hairs in his telescopic sight at the target, and fired the missile. After launch through the cannon, the missile's solid-fueled sustainer rocket ignited, and propelled the Shillelagh to flying speed (source [1] claims a speed of about 4200 km/h (2600 mph), but this seems to be way too high). For the time of flight of the round, the gunner had to keep the cross-hairs pointed at the target. A 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. The missile's 6.8 kg (15 lb) shaped charge warhead detonated on impact. Although strictly a short range (2000 m (6600 ft) max) line-of-sight weapon, the MGM-51A Shillelagh was an accurate missile even against moving targets. There were also some drawbacks, one of which was the relatively high minimum range of about 730 m (2400 ft). From launch until this distance, the MGM-51A flew below the line-of-sight of the tracking system's infrared beam and could therefore not be guided. Because the minimum range was slightly above the maximum effective range of the M551 Sheridan's conventional unguided munition, this created a dangerous "dead range" for the AFV. A Shillelagh missile was also rather expensive compared to conventional anti-armour rounds.

In 1963, the U.S. Army awarded Ford a contract to study the possibility of extending the Shillelagh's range by about 50 percent. In 1964, Ford proposed a slightly longer and heavier, but otherwise essentially unchanged missile. Flight tests of XMGM-51B evaluation rounds began in May 1965, and in October 1966, the extended range Shillelagh was approved for production as MGM-51B. The MTM-51B was the corresponding training round.

MGM-51 (exact model unknown)

To prevent missile roll during gun launch, the Shillelagh used a longitudinal key, which fitted into a keyway inside the gun barrel. The key of the MGM-51A/B was 3.3 mm (.130 in) deep and 25.4 cm (10 in) long. During tests in the 1964 time frame, it was discovered that structural cracks in the barrel occurred after a few hundred Shillelagh shots, and the origin of these cracks could be traced to the missile keyway. It was determined that a less deep key would significantly extend the service life of the barrel. During tests in 1966 with missiles of shallower key, the optimum key depth was found to be 1.9 mm (.075 in). After further test, the shallow-key missile was approved for production and service use in January 1968, and designated MGM-51C. As for the MGM-51A/B variants, there was also a training round of the MGM-51C, designated MTM-51C. Between August 1968 and February 1969, all deep-key MGM-51Bs were converted to MGM-51C configuration. Shallow-key missiles could also be fired from deep-key barrels, but not vice versa, of course. The shallow-key gun launcher was known as M81E1.

The M60A2 - armed with the revolutionary 152mm Shillelagh gun-launcher system, the A2 was also equipped with one of the first laser rangefinders ever fielded. The gun-launcher could fire conventional ammunition with a fully combustible charge, or the Shillelagh laser guided missile.

Apart from the M551 Sheridan, the only other delivery system for the Shillelagh was the M60A2 tank, developed from the M60A1 model via the interim M60A1E1 and M60A1E2. The M60A2 replaced the M60A1's turret with a new 152 mm gun turret compatible with Shillelagh, and the usual load was 13 missiles and 33 unguided rounds. After initial tests in 1966/67, the M60A2 was first fielded in 1974, after delays caused by technical problems. However, the M60A2/Shillelagh system was plagued by severe reliability problems, and was already phased out in 1980.

MGM-51 being loaded into an M60A2

The Shillelagh was in production until 1971, and a total of about 88000 MGM/MTM-51 missiles of all variants were built, including 12500 by Martin Marietta. Phaseout of the M551/Shillelagh system began in 1978, and in 1980 only a single active Airborne Battalion retained the M551. In the U.S. Army National Guard, the M551 was finally retired in 1984. However, the one active Army M551 unit kept these systems until 1991, and actually deployed during Operation Desert Storm (although no Shillelagh shot was fired). It can be assumed, that the last M551 vehicles and MGM-51C Shillelagh missiles were removed from the inventory soon after. The main replacement for Shillelagh as a mobile anti-armour missile was the significantly more versatile BGM-71 TOW.

M-551 Sheridan in Vietnam

Developed in 1959 as a replacement for the M41 light tank and the airborne M56 Scorpion self propelled antitank gun, the Sheridan was intended as an airborne reconnaissance and assault vehicle.

Following a parachute drop, crewmen ready their vehicle for action. Note the cardboard dunning immediately under the main gun barrel, part of the elaborate system to cushion the shock of landing.

Standard Vehicle Data

Type: Light Tank
Crew: 4 (Commander, Driver, Gunner and Loader)
Range: 600 km
Max Speed: 70 km/h (5.8 km/h in water)

Armour:

Assembly: Welding
Hull: Rolled 7039 aluminum alloy
Turret: Rolled and cast homogeneous steel

Fording: Amphibious
Obstacle: Capable of traversing obstacles up to 0.8 meters high
Crossing: Capable of crossing gaps of up to 2.5 meters

Armament:

1 x 152mm Gun/Missile Launcher
1 x 7.62mm co-axial MG
1 x .50 cal on commander's cupola.
8 Smoke Dischargers

In 1968 plans were approved to equip two divisional cavalry squadrons, the 1st and 3rd Squadrons of the 4th Cavalry with the new tank Neither unit actually wanted the Sheridan because it was suspected of being too vulnerable to mines and RPG's.

In a last minute change of plan, the new M551's were sent to the 1st Squadron, 11th Armored Cavalry Regiment and the 3rd Squadron, 4th Cavalry with 'B' Troop 3/4 Cavalry receiving their first Sheridan's in late January 1969.

It was subsequently decided to replace the M48A3 Patton's in cavalry platoons of divisional cavalry squadrons with the M551. Some cavalry platoons of regimental cavalry squadrons were actually using M113 ACAV's as substitutes for the M48A3's in their cavalry platoons and it was intended that the M551 should replace these also. By 1970 almost every cavalry unit in RVN was equipped with the Sheridan.

The M551 suffered from many defects (see below). One particular problem concerned the vehicle's all electric fire-control system which malfunctioned continuously in the rainy season, and despite pre-deployment tests which highlighted these problems - in particular the combustible 152-mm ammunition - and the general unsuitability of the vehicle for the hot and humid Vietnamese environment, the Army sent the M551 anyway. According to Jerry Headley the picture above of 'Hard Core 7',

"... the track belongs to B Troop, 2d Platoon. It was taken in the Ho Bo Woods in Feb '69. I was the Troop Commander at the time. The photo was taken by Army photographers. They also took films. The purpose was to send them to Congress. They were investigating complaints about the Sheridan, i.e., too noisy, gave off a plume of white smoke when moving, etc. Notice the "RPG Screen" in front of the driver. The crew made this themselves as additional protection from RPGs."

The Sheridan was armed with a 152-mm main gun (vehicles dispatched to Vietnam had the guidance system for their ATGW missiles removed) which fired a selection of combustible-case antitank rounds and also the 'beehive' round. Other armament consisted of a co-axial 7.62-mm MG and cupola mounted .50-cal M2 HB for use by the tank commander. When the M551 first appeared in RVN they did not have any armor protection for the tank commander's .50-cal MG. Many crews utilised the armored gun shields from M113's to provide some protection to the tank commander. Eventually, a production armor kit was developed, known as the 'bird cage', to provide all-around protection for the commander.

Whilst the Sheridan had a steel turret it only had a thin aluminum hull which was vulnerable to RPG's. In particular the M551 had a thin underbelly which, unlike the heavy steel belly armor of the M48A3, was very susceptible to damage from mines. As a result, many crews refused to ride inside the vehicle (just as they did with the M113). The Army attempted to remedy this by retro-fitting steel belly armor. In contrast to the M48A3 which could absorb a lot of hits and still continue to fight, in combat the Sheridan was prone to catastrophic explosions (due in part to the highly combustible 152-mm ammunition carried).

Jim Fitzpatrick (11th ACR, '64 - '67) wrote,

"as for the M551 Sheridan tank, they were death traps and most of the troopers I know who rode them hated them. They had explosive shell casings that sometimes exploded when the 551 hit a mine and when RPG and 51 cal. ammo had pierced the thin armor plate of this track. The tanks (M48A3) of the Cav troops were replaced by ACAVs when we went to Nam, only the tank companies of the 11th Cav kept the M48A3s. I personally am glad I never had to ride the 551, although I TC'd an ACAV through an ambush at Suoi Cat on Dec 2 1966."

DESIGN DEFECTS

When asked to highlight some of the problems experienced with the M551, Stanley Homiski, Commo Sergeant with B Troop, 3/4 Cav replied,

"... I can tell you one thing about the Sheridan is that at first we had a lot of radio problems with them. That was because when that 152 MM main gun fired it would lift the tank up off the ground about two feet the second road wheel back and the action of the tank coming back into firing position would severely damage the radio mount. It wasn't shock mounted properly. This was in addition to all the other problems we had with it."

"... electrical problems with the Sheridan happened more during the wet season... we found that due to temperature changes between the daytime (100+ degrees F) and nighttime temperatures (around 70 degrees F) that severe condensation problems occurred. There would be small droplets of water dripping in the turret usually around the area that the radio was installed. At one point we resorted to covering the radio with a poncho to keep out the moisture but this in turn caused problems with the radio starting to overheat due to lack of ventilation."

"... I don't know if you are aware that one of the major problems with it in Vietnam was one of engine failure, the vents would become plugged with jungle vegetation and the damn engine would fail, one of the other things was the main gun ammo - it didn't have a brass shell casing, the whole shell was consumable and you had to keep asbestos covers over the ammo up until you loaded it into the breech."

Additional Sources:

www.designation-systems.net
www.gruntonline.com
members.aol.com/Faessler99
eaglehorse.org
www.globalsecurity.org
afvinteriors.hobbyvista.com
www.redstone.army.mil
www.coldwar.org
usarmygermany.com

On This Day In History

Birthdates which occurred on July 20:
1304 Francesco Petrarch Italy, poet (Italia Mia)
1519 Innocent IX 230th Roman Catholic pope (1591)
1785 Mahmud II Ottoman sultan, Westernizer, reformer
1824 Alexander Schimmelfennig, Prussia, Brig General (Union volunteers)
1890 Theda Bara actress/vamp (Under Two Flags, Cleopatra) (or 0729)
1890 Verna Felton Salinas Calif, actress (Hilda-December Bride)
1919 Sir Edmund Hillary one of 1st 2 men to scale Mt Everest (namesake of the EX firstlady)
1920 Elliot L Richardson Attorney General (1973)/Sec of Defense (1973)
1924 Thomas Berger US, novelist (Vital Parts, Little Big Man)
1933 Nelson Doubleday publisher (Doubleday)/owner (NY Mets)
1938 Diana Rigg Doncaster England, actress (Emma Peel-Avengers)
1938 Jo Ann Campbell Jacksonville Fla, Lawrence Welk's champagne lady
1938 Natalie Wood [Natasha Gurdin], SF, (Gypsy, Rebel Without a Cause)
1939 Judy Chicago [Cohen], Chicago, artist (The Dinner Party)
1940 Tony Oliva ball player, batting champ (AL Rookie of Year 1964)
1941 Vladimir A Lyakhov cosmonaut (Soyuz 32, T-9)
1943 John Lodge bassist (Moody Blues)
1947 Carlos Santana Mexico, musician (Santana-Black Magic Woman)
1957 Donna Dixon Va, actress, Mrs Dan Ackwoyd (Couch Trip, Bossom Buddies)

Deaths which occurred on July 20:
1609 Federico Zuccari Italian Mannerist painter, dies (birth date unknown)
1031 Robert II de Vrome, King of France (996-1031), dies
1454 Johan II, King of Castille, dies at 49
1636 John Oldham, trader in Mass, murdered by indians
1752 John C Pepusch, English composer (Beggar's Opera), dies at about 85
1819 John Playfair, Scottish geologist/mathematician, dies
1923 Pancho Villa, [Doroteo Arango], Mexican rebel, murdered at 55
1944 Brandt, col/German staff chief, dies in bombing
1944 Claus Schenk von Stauffenberg, count/German antifascist colonel, dies
1944 Friedrich Olbricht, German general (July 20th plotter), executed
1944 Heinz Burns, German (Olympic-gold-1936), dies in bombing
1944 Korten, chef gen of Germany Luftwaffe, dies in bomb explosion
1944 Ludwig Beck, gen/chief Germany general staff (July 20th plot), dies
1944 Mertz, German colonel (July 20th plotter), executed
1944 Rudolf Schmundt, gen/Hitler's Army adjunct, dies from wounds
1944 Werner von Haeffen, German lieutenant (July 20th plotter), executed
1951 Abdullah Ibn Hussein Jordan's King assassinated in Jerusalem
1951 Mustafa Shuqri Ashu, tailor/murderer of king Abdullah, shot to death
1954 Blair Moody (Sen-Mich), dies at 52
1973 Bruce Lee, [Lee Yuen Kam], actor (Enter the Dragon), dies at 32
1983 Frank Reynolds news anchor (ABC Evening News), dies at 59
1995 Helmut Erich Robert Gernsheim, photographer/collector, dies at 82

Reported: MISSING in ACTION
1966 BARBAY LAWRENCE---BATON ROUGE LA.
[03/04/73 RELEASED BY DRV, ALIVE AND WELL 98]
1966 DILLON DAVID A.---SPRING VALLEY CA.
1966 HUBBARD EDWARD L.---SHAWNEE MISSION KS.
[03/04/73 RELEASED BY DRV,ALIVE AND WELL 98]
1966 LEWIS MERRILL R.---INDIANOLA IA.
[REMAINS RETURNED 08/29/89]
1966 MC DANIEL NORMAN A.---FAYETTEVILLE NC.
[02/12/73 RELEASED BY DRV, ALIVE AND WELL 98]
1966 MEANS WILLIAM H.---TOPEKA KS.
[02/12/73 RELEASED BY DRV, DECEASED]
1966 NELSON WILLIAM HUMPHREY---FILION MI.
[09/30/77 REMAINS RETURNED BY SRV]
1966 NOBERT CRAIG R.---AVON CT.
1966 PERKINS GLENDON W.---ORLANDO FL.
[02/12/73 RELEASED BY DRV, ALIVE AND WELL 98]
1969 SMILEY STANLEY K.---SIDNEY NE.

POW / MIA Data & Bios supplied by the P.O.W. NETWORK. Skidmore, MO. USA.

On this day...
0514 St Hormisdas begins his reign as Catholic Pope
1031 Henry I succeeds father Robert II as King of France
1773 Scottish settlers arrive at Pictou, Nova Scotia (Canada)
1801 Elisha Brown Jr pressed a 1,235 pound cheese ball at his farm
1808 Napoleon decrees all French Jews adopt family names
1810 Colombia declared independence from Spain
1858 Fee 1st charged to see a baseball game (50cents) (NY beats Bkln 22-18)
1861 Confederate state's congress began holding sessions in Richmond, Va
1862 Guerrilla campaign in GA (Porter's and Poindexter's)
1864 Battle at Stephenson's Depot Virginia: 200 killed or injured
1864 Battle of Peachtree Creek-Atlanta Campaign
1868 1st use of tax stamps on cigarettes
1871 British Columbia becomes 6th Canadian province
1872 Mahlon Loomis receives patent for wireless ... the radio is born
1876 1st US intercollegiate track meet held, Saratoga, NY; Princeton wins
1881 Sioux Indian leader Sitting Bull, surrenders to federal troops
1890 Snow & hail in Calais, ME
1894 2000 fed troops recalled from Chicago, having ended Pullman strike
1903 Giuseppe Sarto elected Pope Pius X
1912 Phillies Sherry Magee steals home twice in 1 game
1914 Armed resistance against British rule begins in Ulster
1917 Pact of Corfu signed: Serbs, Croats and Slovenes form Yugoslavia
1917 WW I draft lottery held; #258 is 1st drawn
1922 Togo made a mandate of the League of Nations
1925 Beirut sultan Pasja al-Atrasj calls Druzen for holy war against France

1927 Lindbergh begins NY flight (Spirit of St Louis)

1930 106ø F (41ø C), Washington, DC (district record)
1933 Vatican state secretary Pacelli (Pius XII) signs accord with Hitler
1934 118ø F (48ø C), Keokuk, Iowa (state record)
1938 Finland awarded 1940 Olympic games after Japan withdraws
1942 Legion of Merit Medal authorized by congress
1942 Women's Army Auxiliary Corps began basic training at Fort Des Moines
1943 Joint Chiefs of Staff question adm Nimitz (landing Gilbert Island)
1944 Pres FDR nominated for an unprecedented 4th term at Dem convention
1944 US invades Japanese-occupied Guam in WW II
1944 Browns Nelson Potter is 1st pitcher suspended for throwing spitballs

1944 Von Stauffenberg fails on an attempt on Hitler's life

1948 Syngman Rhee elected president of South-Korea
1948 US Communist Party chairman William Forster arrested
1949 Israel's 19 month war of independence ends
1950 "Arthur Murray Party" premiers on ABC TV (later DuMont, CBS, NBC)
1954 Armistice for Indo-China signed, Vietnam separates into North and South
1956 France recognizes Tunisia's independence
1960 1st submerged submarine to fire Polaris missile (George Washington)
1960 USSR recovered 2 dogs; 1st living organisms to return from space
1963 Verne Gagne beats Crusher Lisowski in Minneapolis, to become NWA champ
1964 1st surfin' record to go #1-Jan & Dean's "Surf City"
1965 46.18 cm (18.18") of rainfall, Edgarton, Missouri (state 24-hr record)
1967 Race riots in Memphis Tenn
1968 Iron Butterfly's "In-a-gadda-da-vida" becomes the 1st heavy metal song to hit the charts, it comes in at #117

1969 1st men on Moon, Neil Armstrong & Edwin Aldrin, Apollo 11

1970 1st baby born on Alcatraz Island
1974 Turkey invades Cyprus
1976 US Viking 1 lands on Mars at Chryse Planitia, 1st Martian landing
1979 44-kg Newfoundland dog pulls 2293-kg load, Bothell, Wash
1985 Divers find wreck of Spanish galleon Atocha
1988 Michael Dukakis selected Democratic presidential nominee
1989 93ø F, highest overnight low ever recorded in Phoenix Arizona
1990 Justice William Brennan resigns from the Supreme Court after 36 years
1991 Mike Tyson is accused of raping a Miss Black America contestant
1992 Seven people were killed when a test model of the Marine Corps' controversial V-22 Osprey transport aircraft crashed into the Potomac River
1993 Deputy White House counsel Vincent Foster was found shot to death in a park in northern Virginia. His death was ruled a suicide.
1994 OJ Simpson offers $500,000 reward for evidence of ex-wife's killer (FOUR!)
1999 After 38 years at the bottom of the Atlantic, astronaut Gus Grissom's Liberty Bell 7 Mercury capsule surfaced.
2000 A federal grand jury indicted two former Utah Olympic officials for their alleged roles in paying $1 million in cash and gifts to help bring the 2002 games to Salt Lake City.

Holidays
Note: Some Holidays are only applicable on a given "day of the week"

Columbia-1819, Tunisia-1956 : Independence Day/D¡a de la Independencia
US : Moon Day (1969)
US : National Nap Day
National Lamb and Wool Month

Religious Observances
RC : Comm of St Margaret of Antioch, virgin/martyr (3rd cen)
Old Catholic : Feast of St Jerome Emiliani, confessor
St. Wilgefortis Feast Day
Commemoration of Elijah (Elias), greatest of the prophets (Roman and Greek Churches).

Religious History
1648 The Westminster Larger Catechism was adopted by the General Assembly of the Churchof Scotland at Edinburgh. This and the Shorter Catechism have both been in regular use amongPresbyterians, Baptists and Congregationalists ever since.
1726 Colonial clergyman Jonathan Edwards, 23, married Sarah Pierpont, 16. Theirmarriage prospered for over 30 years, before his premature death in 1758. Sarah herself diedonly six months later, at 48.
1877 Birth of Jesse Overholtzer, who in 1937 incorporated Child Evangelism Fellowshipin Chicago. Today the CEF mission agency works in over 60 countries worldwide.
1910 The Christian Endeavor Society of Missouri began a campaign to ban all motionpictures that depicted kissing between non-relatives.
1962 Pope John XXIII sent invitations to all 'separated Christian churches andcommunities,' asking each to send delegate-observers to the upcoming Vatican II EcumenicalCouncil in Rome.

Source: William D. Blake. ALMANAC OF THE CHRISTIAN CHURCH. Minneapolis: Bethany House, 1987.

Thought for the day :
"Liberty is always dangerous, but it is the safest thing we have."

Things To Do If You Ever Became An Evil Overlord...
See a competent psychiatrist and get cured of all extremely unusual phobias and bizarre compulsive habits which could prove to be a disadvantage

PUNishment of the the day...
Working for the IRS is a hard job because it is so taxing.

Dumb Laws...
St. Cloud Minnesota:
Hamburgers may not be eaten on Sundays.

How to Annoy Osama bin Laden If You're Invited To A Dinner Party At His Secret Afghan Lair...
Mine his bathroom.