Operational experience in South Vietnam rapidly demonstrated a need to provide armour protection for the M113's machine gun, as the crew commander who operated the machine gun was highly vulnerable when using the weapon. From August 1965, M113A1s began to be fitted with armoured shields that comprised a front plate and angled wings on each side. They were built by Army workshops in South Vietnam to varying designs, and were similar to shields fitted to the Army of the Republic of Vietnam's M113s While the shields provided some protection, the gun position remained unprotected from the sides and rear.
As an interim measure to improve protection, 19 M113A1s in Vietnam and one in Australia were fitted with Model 74C turrets between September and November 1966. These provided all-round protection, and were armed with two M1919A4 Browning machine guns. The turret was very cramped, and its traverse mechanisms rapidly wore out. All of the Model 74C turrets were withdrawn by December 1968.
The T50 turret was selected as the standard turret for Australian M113s. The US Army had fitted one of these turrets to an M113 on an experimental basis in 1964. The Australian Army was aware of this experiment, and began its own trials of the turret in April 1966. The trials team delivered a favourable report, and the turret was approved for service in late 1966.
M113A1s fitted with T50 turrets began to arrive in South Vietnam in August 1968. Almost all of the Australian Army's M113A1s were eventually fitted with these turrets. The turret was initially armed with two L3A3 machine guns (an improved version of the M1919A4), but some were later fitted with a M2 Browning and a M1919A3.
The turret was regarded as unsatisfactory by soldiers, as it was cramped and it proved difficult to keep the guns aimed when the vehicle was moving. The turret was also very slow to rotate, which led to delays in engaging targets. To free up space, the right-hand side L3A3 machine gun was removed from all the T50 turrets in South Vietnam by early 1970; these guns were instead fitted to the roof of the turret using a pintle mount.
Fitting the machine gun on the turret roof also allowed it to be quickly brought to bear on targets, though the commander lacked armoured protection while using the weapon. The Australian Army is one of only two M113 operators to have fitted turrets to the type
