m551

The M-551 General Sheridan

       The concept which was later to produce the Sheridan was first outlined in August 1959. The US Army was looking for a lightweight armored vehicle which was: 1) able to survive on the modern battlefield 2) light enough to be dropped from the air    3) equipped to knockout any enemy vehicle. This last point we will see was to be a source of endless problems. This new weapon was slated to replace the M-41 light tank and M-56 self-propelled gun. Major automotive companies scrambled for a design.
      By May 1960, the pending contract had been won by the Allison division of GM. After creating a full scale mock-up, the Army evaluated and gave an approval for further production in December of 1961. A prototype was made in 1962; Allison's developer's had keenly met all the army's demands and somehow managed to mate the XM81E7 gun/missile system to the turret.
      The Sheridan proved to be a veritable Swiss army knife on the modern battlefield; able to deal with many local conditions. It's huge engine allowed it a speed of 43.48 mph(1) and the engine's fuel reservoir allowed for 373 mile-radius of operation. The commander, driver, and gunner all had excellent fields of visions and even infrared equipment for night actions.
      The Sheridan's aluminum hull made it perfectly light enough to be dropped from the air. It's crew of four would jump as well and be able to use it once it hit the ground. The aluminum hull also allowed for the vehicles ability to swim across rivers at the speed of 3.6 mph, if fitted with a flotation device. The armor however; had it's problems. In Vietnam; mines and even heavy machine guns were able to penetrate it!
    The Sheridan's greatest flaw was it's substantially to heavy and technology ridden main armament, a 152mm gun(2). At the army's behest the XM81E7 system was mounted. Not only was it a conventional gun, gut; also a missile launcher. This weapon had several possible shells all with their own advantages.

Name/notes	Range/notes
MGM-51 Shillelagh Missile (3 ft and 10in long weighing 58 pds) Could destroy any tank.	A minimum range of 3,000 meters. The Maximum range is 4,000 meters
M-49 anti-tank tracer round	7,450 meters
Canister or "shot shells"	7,450 meters
M409 HEAT	800 meters
White Phosphorus	7,450 meters

    Despite the high-tech abilities of this mammoth gun it was dangerous to it's crew. The crew needed to spend approximately 10 seconds bracing before firing. If this was not done the consequences were severe. The gun swivels with the force of the blast and the tank can be displaced several meters. The commander suffers from a powerful blow to the ribs and for the gunner things are even worse. The recoil of the gun could give a black eye to the gunner and if he forgot to take his hand of the traversing wheel his wrist would be forcefully broken. The vehicle's missile system is broken 33% of the time and the laser finder also has a chance of being damaged beyond the repair capabilities of the crew if the gun is fired. For those willing to fire a second round they would often find a melting residue of combustible casing to deal with. If another round was loaded, the burning casing could cause it to fire prematurely. In light of these side effects the crew would've felt safer firing the 7.62 mm coaxial MG or the .50 Caliber MG in the Commander's position.
    It is important to note however that this complicated missile system is relatively easy to aim, a gunner merely has to put the target in his sites and fire, data is feed in-flight to the missile by an infrared sensor. The name "sudden death" fully applies to a missile that has a velocity of 1,881 ft per second. Under ideal conditions a 90% accuracy rate can be achieved.
    Between 1965 and 1970 over 1,700 of these war dogs rolled off the assembly line. First, they formed armored Calvary squadron's in airborne, armor, and infantry divisions. This new weapon was integrated into many armored cavalry regiment's reconnaissance platoons. It replaced either a recon variant of the M113 and the M48 in some units(3). Within a year it had been deployed to Europe, Korea, and Vietnam.
    Lessons were learned quickly on the Vietnam battlefield. The Sheridan lacked the power to crash through the jungle recklessly like an M48. Instead, the vehicle was used more effectively in ambush, recon, airmobile and convoy duty.
    In country; a Sheridan's crew often loaded the vehicles exterior with fuel , smoke grenades and strapped on ammunition. Sometimes they lashed on a storage basket like the kinds found on must shopping carts! The American flag was displayed on the vehicles antenna. The vehicle also tended to carry a stretch of chain-length fencing to protect it's thin armor from RPG attacks at night. Wire-mesh was also used to protect the lights and the driver's position. The commander's position usually received further shielded as well.

After the US withdraw from Vietnam, the Sheridan's use declined. It was replaced by the M-60 in all but; National Guard units by the 1980s. However the vehicle was still in use by the 3rd Battalion, 73rd Armored Regiment of the 82nd Airborne during the Gulf War. For service in it's second conflict the vehicles night vision capabilities was extended to the entire crew. Perhaps it was nostalgia that saw this final usage of this vehicle by the 82nd, much like the Marines continue to use the Vietnam-era "Cobra" helicopter. By 1995 a mere 100 remained in the US Army. These remaining few are dressed as Soviet vehicles and used for targets. For more information about this program: http://call.army.mil/call/trngqtr/tq3-99/osv.htm. An image of a Sheridan from the Gulf War is available at www.thepicturecollection.com

(1) in contrast the modern M1 Abrams can manage 41 mph.
(2) During the Persian Gulf War; many critics were concerned that the M1 Abram's 105mm gun would prove no-match for the "large" 128mm gun fielded by the Iraqi's on their soviet armor.
(3) The M48 Patton and the M551 Sheridan were the only tanks crewed by US servicemen in Vietnam. Sources: Armor in Vietnam, Modern Elite Forces, Concise Color Guide Modern Fighting Vehicles, "Strategy & Tactics" September/October 1977, and "Vietnam" Magazine April 1999.

Name: M551 "Sheridan"
Type: Air-Mobile Assault Tank
Dimensions: Length 6.299m, Width 2.819m, Height 2.94m
Weight: 34,826lb (loaded) 29,896lb (unloaded)
Crew: 4
Vehicle Range: 600 km
Engine: Detroit Diesel 6VT53T developing 300 hp at 2,800 rpm.
Max. Speed: 70 km/h (5.8 km/h water)
Fording: Amphibious
Vertical Obstacle: .8 m
Gap Crossing: 2.5 m
Armament: 1 x 152mm gun/missile launcher, 1 x 7.62mm co-axial MMG, 1 x 12.7mm HMG AA gun, 4 smoke dischargers on either side of the turret.
Load: 10 Shillelagh missiles, 20 conventional rounds, 3,080 rounds of 7.62mm, and 1,000 rounds of 12.7mm

I'll add more specifications as soon as I get my hand on Jane's. The next page contains emails I recieved from a Driver of the Sheridan in Vietnam. His accountant is awesome please read:

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