US Armour in Vietnam - the M113 and variants - Part 1

Page Title - US Armour
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The M-113 Armoured Personnel Carrier
and Variants - Part 1


Known as the "Green dragon" to the VC in the early stages of the war, the M113 was destined to become one of the most successful armored vehicles of all time, seeing action in Vietnam on a country-wide scale from the DMZ to the Delta.

Standard Vehicle Data

  • Type: Armoured Personal Carrier
  • Crew: 2 + 11 passengers
  • Range: 483 km
  • Max. Speed: 67.5 km/h (5.8 km/h in water)
  • Armour: 12-38 mm, provided protection from small arms and shell fragments only.
  • Fording: Amphibious
  • Obstacle: Capable of traversing obstacles up to 0.6 meters high
  • Crossing: Capable of crossing gaps of up to 1.68 meters
  • Armament: 1 x .50 cal on commander's cupola.

Early versions of the M-113 (see Picture Gallery) were armed with a single .50 caliber machine gun. There was no armored protection for the .50 cal MG operator. Sandbags were often stacked around the rear hatch to provide some cover for the troops as well as a means of steadying their weapons while the vehicle was in motion. Early versions were powered by a petrol engine but the later M-113A1 substituted a diesel engine.

Standard M-113, mounting a single .50 caliber machine gun

The first M-113's reached RVN in 1962. Originally destined for US units in W. Germany, 32 M-113's  were used to outfit two ARVN mechanized company's fighting the VC in the Mekong Delta.

These company's were modeled on US Army mechanized rifle company's. Each was organised into 3 rifle platoons with 3 M-113's in each platoon. A support platoon with 4 M-113's  carried three 60mm mortars and three 3.5-inch bazookas. 

Standard M113

There was also a company HQ section of 2 M-113's. All the vehicles were armed with a single .50 caliber M-2 HB. In addition, a further eighteen .30 caliber Browning's were distributed throughout the two company's.

During the course of 1962, the ARVN mechanized rifle squadron was modified and the 60mm mortars were replaced with three 81mm mortars and the 3.5-inch bazookas were replaced by a single 57mm recoilless rifle

Standard M113 showing crew exposure to fire

The first M113s were powered by a 209HP Chrysler 75M petrol engine. By 1964 the M113 had been superceded by the updated M113A1. The M113A1 was fitted with a General motor's 215HP Diesel engine which gave it an improved performance over the earlier M113.

Despite being designed as an armored infantry vehicle to be used for carrying mechanized infantry into combat with armored columns of M-48's and M-60 main battle tanks on the plains of Europe, the ARVN units started using them as armored infantry combat vehicles in their own right. Early M-113's supplied to the ARVN were armed with a single M-2 .50 cal heavy machine gun on a pintle mount attached to the commander's cupola. Unfortunately these early M-113's provided no protection for exposed crew members, in particular the commander who manned the .50 cal machine gun. The loss of 14 ARVN gunners at the Battle of Ap Bac glaringly highlighted the need for some additional crew protection. Consequently the ARVN began furnishing their vehicles with  makeshift gun shields.


The hull of the M-113 is fully watertight with all hatches having rubber seals which allows the vehicle to cross bodies of water and slow moving streams.

To become amphibious, the vehicle driver turns on two bilge pumps and lowers the trim vane.

Standard M113 Fording Stream

The trim vane is extended forward and helps maintain the correct balance of the vehicle in the water. It also prevents water from flowing over the front of the vehicle and into the drivers position or the front-mounted engine.

In the water the vehicle is propelled by the forward motion of it's tracks and could reach a speed of 3.5mph. Due to the fact that most crews severely overloaded their vehicles with stowage both inside and out, the amphibious capabilities of the vehicles were generally severely degraded and rarely used.


 ACAV's crossing flooded paddy fields

M-113 ACAV

Following lessons learned, in particular the loss of 14 ARVN .50 cal gunners at the Battle of Ap Bac in January 1963, the standard M113 was upgraded both in armament and armour protection to the M-113 .

Two M60 GPMG's were mounted, one either side of the rear hatch, and fitted with protective gun shields. An FMC-designed armoured gun shield/turret combination was also added to the commanders cupola to afford him protection when manning the .50 cal machine gun. This vehicle was designated the M-113 Armored Cavalry vehicle (ACAV - see Picture Gallery).

Although the M-113 was initially designed to carry a full 10 man rifle squad in addition to the two-man crew, the Cav doctrine was actually to fight directly from the vehicle on the move and it was intended not to dismount the infantry unless in extremis. As a consequence of this doctrine, the vehicle became a mobile fire platform and stowage of prodigious quantities of ammo and other equipment considerably reduced the internal troop carrying capacity.

Normal crew for the ACAV was a driver, commander (who manned the .50 cal), two M-60 gunners and two loaders, one of whom would also be armed with an M-79 40mm grenade launcher. Typical ammo loads consisted of 3,500 rounds of M2 .50 caliber, 8,500 rounds of 7.62mm m-60, 5,000 rounds of 5.56mm M-16 and 150 40mm M-79 40mm grenades.



As a result of lessons learned, when the 11th ACR shipped to RVN their M-113's were fitted with the new FMC gun shields and had additional M-60's mounted either side of the rear top hatch. The 11th ACR coined the term ACAV which soon became the 'official' designation of this modified M-113.

ACAV turret mount

The FMC gun-shield/turret combination was a design which built upon the earlier attempts of ARVN units to provide some frontal protection for their machine gun operators and whilst attempts to protect the commander proceeded, no attempt was made to afford similar protection to troops fighting from the rear passenger compartment of the vehicle.

View of ACAV showing gun positions

The ACAV was set to remedy this by providing gun shields for the additional M-60's. Movable arms with sockets were bolted to the top plate adjacent to the rear personnel hatch. The gun shield had the standard machine gun mount to take the M-60 machine gun which could be easily installed.

ACAV M60 mount

Travel locks were provided so that the weapon could remain installed and ready for use during transit. The shields incorporated a feed tray for belted ammunition. Rotating arms provided for a full field of fire and a minimum depression angle for close-in fire.

More ACAV's!

A removable socket could also be installed on the under-side of the rear personnel hatch cover so that when it was thrown back in the open position an M-60 could be mounted for firing to the rear of the vehicle. Picture evidence tends to suggest that this particular option was rarely employed.

As additional protection, troops fighting from the rear compartment often built sandbag parapets around the side of the rear top hatch.

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Next Page


Armor of the Vietnam War; (1) Allied Forces, Michael Green & Peter Sarson, Concord Publications Ltd

Armor in Vietnam; A Pictorial History, Jim Mesko, Squadron/Signal Publications Inc.



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