Armored cavalry assault vehicle m113
IMPROVISED FIGHTING VEHICLES
The M113 armored personnel carrier was introduced into Vietnam when two ARVN (Army of the Republic of Vietnam) companies were organized and equipped in April 1962. Although it violated the doctrine promulgated by their American advisors, the Vietnamese insisted on fighting mounted in their vehicles, using them as light tanks.
The M113 is normal armament of one .50 caliber machine gun was supplemented by additional weapons mounted on top of the vehicle. This method of operation proved to be extremely effective under the conditions prevailing in Vietnam and eventually it was adopted by the American advisors. However, by early 1963, it was obvious that shields had to be provided to protect the gunner using the externally mounted weapons.
At first, they were fabricated locally and consisted of a variety of configurations. Later, they were manufactured on Okinawa and shipped to Vietnam. On 6 April 1966, FMC was authorized to design and manufacture two prototype shield kits from mild steel. Design work began under Group Leader Cal Walker and Senior Project Engineer John Giacomazzi using drawings with Vietnamese captions and penciled in translations.
They also had a description of the combat requirements and five photographs of the shields improvised in Vietnam. That shield consisted of three pieces of armor, one in front and one on each side of the commander's hatch. The rear was protected by the open hatch cover. The FMC kit followed this arrangement, but the two pieces of flat angular side armor were replaced by curved sections. The design team also added a 7.62mm machine gun mount on each side of the cargo hatch.
A shield was provided for each bringing the total number of armor components to five. One of the 7.62mm machine guns could be shifted with its shield to a removable pintle mount on the open cargo hatch cover allowing fire to the rear of the vehicle. This complete set of armor shields was designated as the A kit. Another version, consisting of only the three piece shield for the commander's hatch and the .50 caliber machine gun, was designated as the В kit. The latter was provided for installation on the mortar carriers.
After inspection of the two soft steel prototypes, FMC received a contract to produce 385 kits. Later, this initial contract was increased to 476 kits and all were shipped by 15 July 1966. Some of these were installed on the M113A1 armored personnel carrier being converted for use as fighting vehicles by the 11th Armored Cavalry Regiment. With this armament, they were referred to as the armored cavalry assault vehicle (ACAY) and were used by the 11th ACR when they deployed to Vietnam.
The kits were then used to convert many of the M113 series vehicles to the ACAV configuration. The normal crew for the ACAV was five or six consisting of the driver, commander, two or three machine gunners, and a grenadier armed with a 40mm M79 grenade launcher. Other weapons that could be installed on the ACAV included the 40mm XM175 automatic grenade launcher and various recoilless rifles.
As described earlier, a vulnerability reduction kit was developed to reduce the damage from mine explosions. This kit included a steel armor plate installed on the bottom front of the vehicle. It was attached by four bolts to the lower front armor and it extended back under the hull past the second road wheel suspension arm. Brackets secured the armor plate to the hull side armor.
In December 1963, the U.S. Army Combat Developments Command published "A Study of Alternatives for a Post 1965 Infantry Combat Carrier". Later, this became the mechanized infantry combat vehicle (MICV). Since this vehicle would not be available for several years, the M113 received numerous modifications to provide an interim fighting vehicle.
The first approach was to install firing ports and vision blocks in the side armor and rear ramp of the M113 to allow the troops to orient themselves and use their individual weapons. The first of the modified vehicles had four sets of firing ports and vision blocks on the right side, but only three sets on the left because of the interference of the fuel tank in the left rear sponson. Two sets of firing ports and vision blocks were in the rear ramp.
The firing ports and vision blocks protruded from the side armor slightly increasing the width of the vehicle. Several mounts were installed at the commander's station. These included the standard commander's cupola from the M113 armed with the external .50 caliber machine gun. The A kit of armor shields was mounted on at least one vehicle. The Model 74 twin machine gun cupola also was installed as well as the M27 cupola armed with the 20mm gun Ml39. This vehicle was the first of several designated as the XM734.
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