Developed from the M47 "General Patton" tank, the M48 was the mainstay of the U.S. Army and Marines in Vietnam. Some 11,703 M48s were built between 1952 and 1959. The M48, which was designed for combat in Europe against Soviet tanks, originally carried 90mm guns, but upon modification to the M48A5 standard they were given the British 105mm.
The M48A3's 90mm cannon, and its broad range of available ammunition types, was the major reason the M48s were sent to Vietnam, rather than the later M60 series. The 90mm came with a variety of ammunition choices that proved critical in Vietnam combat. Tankers could draw on the devastating canister round for use in thick jungle and wooded areas, high explosive plastic (HEP) for taking out bunkers and structures of all types; HE and HE Delay for use against personnel and fortifications; white phosphorus (WP) for marking targets and for use against personnel; and HEAT for use against other tanks and fortifications.
The normal basic load for 1966-68 tankers might include equal numbers of canister, HE, and a WP-HEP mix. Later loads would include HEAT, due to the introduction of armored vehicles by NVA forces in the tri-border areas of operation. Precluding the use of the M60 tanks in Vietnam was the lack of HE and canister rounds for their 105mm tank guns.
The M56 Scorpion self-propelled Antitank Gun was a fully tracked 90mm gun developed in the 1950s to provide airborne troops with a mobile anti-tank weapon. Used by airborne battalions and airborne infantry tank companies in the 1960s.
When controlled by the SCR 584 radar set, the US 90mm M1 Anti-aircraft Gun was the finest anti-aircraft gun of World War Two. During the campaign agains the V-1 they operated 22 hours a day with two hours a day for maintenance. Like every other mechanical device, the gun wore out after prolonged use. The life expectancy of the gun tube was 1,500 to 2,000 rounds and many batteries wore out three or four sets of tubes over the course of the campaign. After the third wore out, the gun slide had to be replaced as well. Due to shortages of replacement barrels some tubes were retained until they fired as many as 2,500 rounds but this was a dangerous practice. When the tube became that worn, muzzle velocity grew erratic and, in some cases, the lands in the tube began to peel. For much of the four months of December 1944 to March 1945, nearly every 90mm anti-aircraft gun barrel produced was sent to Antwerp. The anti-aircraft units in the Pacific and the Mediterranean had to wait. In February ammunition ran low despite emergency deliveries by air. What they accomplished was the downing of 2,183 V-1s. In one week near the end of the campaign, they succeeded in shooting down 94% of the incoming V-1s. To accomplish this, they expended 532,000 rounds of 90mm ammunition.
During the Korean Conflict, 90mm Antiaircraft gun battalion and automatic weapons battalions served effectively in the ground role. The antiaircraft battalion now organic to division artillery was equipped with twin 40mm. guns and quad .50-caliber machine guns, all self-propelled. In addition to the same weapons, a few nondivisional antiaircraft artillery battalions in Korea were armed with 90mm. guns.
The Army formed its Army Antiaircraft Command (ARAACOM) in July 1950. ARAACOM had three types of AAA battalions: 90mm, l20mm and AW. The most numerous were the very accurate, high-velocity 90s. With an altitude capability of 30,000 feet and a range of 14 miles, the 90mm gun was a proven performer that had scored numerous kills during the Second World War, especially when it was linked to a fire control computer and fitted with VT proximity fuses. One 90mm gun could put 20 to 25 rounds in the air every minute, so a complete battery of four guns firing at an aircraft could put a lot of steel on target. Peak deployment of the 90mm gun occurred in 1953, when 42 battalions were on line. With each battalion having four batteries, and each battery having four guns, the result was 672 guns pointing skyward to protect the United States. The gun crew consisted of eight or nine men and included a section chief, loader, gunner, azimuth pointer, elevation pointer and a three- or four-man ammo section. The crew both operated and maintained the weapon, which could fire its 24-pound projectile 30,000 feet into the air.
A Foreign Military Sale (FMS) was developed for the Light Armored Vehicle-Assault Gun (LAV-AG). The main armament of the LAV-AG is the a 90mm cannon, providing direct fire, and kinetic energy and chemical energy capabilities to the light forces. This development is being done by foreign companies. The US Government was contracted to evaluate the performance and safety of the entire system. CCAC is evaluating the performance and safety of the 90mm ammunition.
On 22 July 1997 the Department of Defense has notified Congress that the Government of Saudi Arabia had requested the continuation of the U.S.-supported effort to modernize the Saudi Arabian National Guard (SANG) to include 130 90mm Turret Weapon Systems for integration into Light Armored Vehicles. Also included for the turret systems are modification/upgrade of the chassis, 130 M240 machine guns, 130 M2 .50 caliber machine guns, testing, spare parts, 169,490 rounds of 90mm ammunition, associated equipment, design and construction of range and maintenance facilities, U.S. Government and contractor management, training and technical services, and full logistical and training support. The estimated cost is $1.075 billion.
The Foreign Military Sales program manages government-to-government purchases of weapons and other defense articles, defense services, and military training. A military buying weapons through the FMS program does not deal directly with the company that makes them. The Defense Department serves as an intermediary, usually handling procurement, logistics, and delivery and often providing product support and training. FMS should be distinguished from the Direct Commercial Sales (DCS) program, which oversees sales between foreign governments and private US companies, and the Foreign Military Financing (FMF) program, which provides grants and loans for FMS and DCS purchases.
Security Assistance Organizations (SAOs), military personnel stationed at US embassies, promote the sale of U.S.-produced defense items and carry out most tasks associated with managing FMS "cases," or agreements to make a sale. SAOs advise foreign defense ministries on potential military purchases, often by coordinating "security assistance surveys" to assess perceived needs and occasionally by aiding the development of procurement plans.
Ammunition for the 90mm recoilless rifle is issued in complete fixed cartridges. The term "fixed" means that the projectile and the cartridge case are crimped together. This insures correct alinement of the projectile and the cartridge case. It also permits faster loading because the projectile and the cartridge case are loaded as one unit. The rear end of the cartridge case is made of frangible material that is completely destroyed when fired.
There are three authorized rounds for the 90-mm recoilless rifle, M67. These are TP M371, HEAT M371E1, and 90-mm canister, XM590E1. The target practice (TP) round is not standard, but it was available for issue in certain areas. It is ballistically identical to the high explosive antitank (HEAT) round but contains only a small spotting charge as the projectile filler. The 90-mm canister round, XM590E1, is a fixed type antipersonnel found which functions at muzzle action.
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