Austarmycrest.gif (8966 bytes)Australian Military Vehicles Research

Australian Modifications to the M113A1 FOV in Vietnam

The terms "left", "right" "front" and "rear" used in this article are as viewed when standing at the ramp of the vehicle facing forward or to the power pack.

Background 1962-1972

The Australian Army trialled the British FV432 armoured personnel carrier and the US Army M113 during 1962-63. As a result of these trials an order was placed for Carrier, Personnel, Full tracked, Armoured M113A1 (Australian).

The Australian version of the M113A1 came with modifications, including a cargo hatch with a ventilation blower and filter units and about an inch (2cm) of foam blankets adhered to the inside hull roof. The A1 version had a diesel engine replacing the earlier petrol fuelled M113.

The first M113A1s arrived in early 1965 and on 27 May 1965 ten M113A1s were sent as part of Force Trimdon to South Vietnam arriving in early June 1965.

The M113A1 armoured personnel carrier (APC) as well as other members of this family of vehicles including the M125A1 81mm mortar carrier, M577A1 armoured command vehicle, M579A1 fitters vehicle and M113A1 Saladin turreted fire support vehicle served in Vietnam up to February 1972.

Modifications in South Vietnam

Gun Shields

Shortly after deploying to South Vietnam it was found that the commander of the vehicle who operated the pintle mounted 50 calibre machine gun was left exposed from the waist up to enemy fire. The solution to this was the attachment of a machine gun shield to the pintle mount. Initial gun shields were rough affairs with sharp edges and made from 5/8 inch steel plate. Later more professional gun shields were made and used Ĺ inch steel plate that provided protection from 7.62 and 12.7mm ammunition. There were several designs of the gun shield over time in Vietnam. 1 APC troop ( ten APCs) were all fitted with gunshields by August 1965

These gun shields were fitted to the personnel carrier, mortar and fitters versions of the M113A1 (Aust) serving in South Vietnam.

Change of Fuel tanks

The early M113A1s were fitted with an integral fuel tank. This was a fuel tank that was welded directly to the vehicle structure in the left rear corner above the track sponson. This metal box housed a rubber fuel bladder. The normal operations of the vehicle tended to bend the hull and soon the welds of the fuel tank would crack and eventually leak diesel fuel into the vehicle. This was corrected by the removal of the integral fuel tank and was replaced by a bolt / strapped in fuel tank. This became a standard production fitting in all new M113A1s from about 196X.

The original build M113A1s with integral fuel tanks can be identified by an oval inspection panel around the fuel cap located in the left rear hull roof. By the late 1960s most integral fuel tanks had been replaced by the bolt in version. Photographic evidence suggests that the factory produced non integral fuel tank manufacture ceased with Australian army registration number (ARN) 134296. This means that the first 150-200 M113A1s delivered to the Australian Army were of this type. This means than most of the 190 M113A1 APC, Fitters and mortar carriers serving in Vietnam would have featured this fitting.

Engine access panel

The M113A1s that were delivered to Australia had a single large internal access panel to the engine. This panel was replaced by a two full width but narrowed access panels and by early 1970 production carriers were delivered with this as a standardised to this fitting.

M74C Twin 30 calibre machine gun turret

As an interim measure pending a final turret selection the Army decided to purchase a limited number of  Model 74C turret because it was a simple drop in type of weapons system and fitted the standard commanderís cupola position.

In order to provide more protection for the M113A1 commander who operated the weapons twenty Model 74C turrets were ordered in March 1966. The turrets were armed with two 30 calibre machine guns. (Explain us type and ammo feeding problems) During November Ė December 1966 these turrets were fitted to Alpha and Bravo vehicles. The turrets had a few problems with and only four were in service by December 1968. By March 1969 the last turrets were returned as unserviceable to 2 Advanced Ordnance Depot at Nui Dat Vietnam.

It is interesting to note that at least two of the twin 30 calibre machine gun mounts were removed from the M74C turrets and fitted to other carriers in place of the .50 calibre machine gun and shield. M113A1 APC -  ARN 134203 and a fitter both had this arrangement in Vietnam for at least a short time.

T50 (Aust) turret

The T50 (Australia) turret was ordered in two versions (i) twin 30 calibre machine guns and (ii) a combination of one 30 and one 50 calibre machine gun. The twin 30 was seen as a weapons system for an APC Regiment. The 50/30 combination was seen as a Cavalry Regiment type of weapon.

The fitting of the T50 (Aust) required several modifications to the M113A1:

The first turrets arrived and were fitted on July 1966. By the end of the Vietnam conflict most of the M113A1 with T50 turrets were still equipped with the 30/30 combination.

Driverís hatch

During fitting of the T50 turrets the drivers hatch cover hinges are relocated. This caused the hatch cover to overlap the edge of the vehicle when in the open position. Defect reports disclosed that the hatch cover struck trees, damaging the hatch hinges. The hatch hinges were relocated so that the hatch cover when open is inboard the vehicle. A small piece of the hatch was also cut off so that it did not interfere with the T50 turret during the opening of the hatch.

Depression rail

A gun depression rail was attached to the side of the turret riser ring. This was fitted to stop the possibility of the turret guns firing into the crew compartment through the cargo hatch. The rail was often bent due to crewmen standing in the cargo hatch using it as a grab rail.

Sponson armour (from August 1969)

As the Australian troops exerted their influence over their area of operations in Phouc Tuy Province, the Vietcong started to use mines more regularly. The danger area on the M113A1 was the forward areas of the vehicle as vehicle detonated mines with their tracks. The solution to this problem was the fitting of an armour plate under the sponson above the first three road wheels. The single armour plate was bent rather than two plates welded to give a better strength. This was originally fitted to the left side sponson mainly to protect the driver. Soon the sponson armour was fitted to both sides. As these plates were welded into place they remained on vehicles post Vietnam.

Belly mine protection plate (from August 1970)

As the power of the anti tank mines and improvised mines increased it became necessary to add a 38mm aluminium armour plate to the floor of the M113A1. This was held in place by two rows of bolts per side and about 150mm up the front of the lower hull. When the vehicles returned to Australia after the Vietnam conflict the belly armour was removed to save weight and could be reattached as required.

Some of these belly armour plates were loaned to the New Zealand Army when some of their M113A1 served in Bosnia in 1996.

Collapsible footrest (from May 1970)

When a mine exploded under the M113A1 the impact was transferred through the hull and inevitably the driverís feet were damaged because the left foot rested on a peg attached to the hull. This peg was replaced by a collapsible footrest designed in Australia and fitted to all M113A1s. This was a late development and the first footrests were delivered by mid May 1970. The US Army introduced the collapsible footrest to their M113A2/ A3s in the mid 1990s.

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