M113 Armored Personnel Carrier - Basic Variants

Basic Variants

M113

Original version, powered by 209 hp (156 kW) Chrysler 75M V8 petrol engine.

M113A1

Starting in 1964, the gasoline engine was replaced with a 215 hp (160 kW) diesel engine, to take advantage of the better fuel economy and reduced fire hazard of the diesel engine. The suffix A1 was used on all variants to denote a diesel engine, i.e. an M106A1 was an M106 mortar carrier equipped with a diesel engine.

M113A2

In 1979 further upgrades were introduced, including cooling and suspension improvements and smoke grenade launchers on the glacis plate. The suffix A2 is used on all variants to denote upgrade to A2 standard.

M113A3

In 1987, further improvements for "enhanced (battlefield) survival" were introduced. This included a yoke for steering instead of laterals, a more powerful engine, external fuel tanks and internal spall liners for improved protection. The suffix A3 is used on all variants to denote upgrade to A3 standard.

M113 Armored Cavalry Assault Vehicle (ACAV) variant

The "Armored Cavalry Assault Vehicle" or "ACAV", was a concept and field modification pioneered by the South Vietnamese Army (ARVN) in 1963 during the Vietnam war. ARVN troops utilized the M113 armored personnel carrier as an infantry fighting vehicle, and more often than not, as a light tank by fighting mounted rather than as a "battle taxi" as dictated by U.S. Army doctrine.

After it was found that the commander and cargo hatch positions were extremely exposed and the commander and troops hence vulnerable to enemy fire, the South Vietnamese engineers thought out a simple and cheap remedy to this problem: Initially field expedient shields and mounts were made from sunken ships, but this was soft metal and could be penetrated by small arms fire. Finally armor plate, from scrapped armored vehicles was used; this worked well, and by the end of 1964 all ARVN ACAVs were equipped with gun shields. For the US Army, ACAV sets were produced industrially in Okinawa for the .50 cal. machine gun, and rear aft and starboard M60 machine gun positions. Finally, the ARVN's ACAV modifications were adopted by the US Army in Vietnam, and by 1965 the full ACAV set was mass-produced in the U.S. The kit included shields and circular turret armor for the commander's M2 .50 caliber machine gun, and two additional 7.62 mm M60 machine guns, again with shields, fitted on either side of the top cargo hatch. This kit could be retrofitted to any M113. ACAV sets were sometimes fitted to the M106 mortar carrier, but the different rear hatch found on this vehicle required the left M60 machine gun to be fitted to the extreme rear instead of the side. Many kits were added in the field, but at least in the case of the 11th Armored Cavalry Regiment, the vehicles had their ACAV sets installed in the U.S. prior to their deployment to Vietnam in 1966 from Ft. Meade, Maryland. Additional armor in the form of a mine protective kit under the hull was also frequently fitted.