CM-21 Armored Vehicle

At the end of 1967, the United States and the Republic of China (Taiwan) signed the Third-Nation Overhaul Program and began to repair US military equipment in Vietnam until the end of the Vietnam War. This allowed the RoC to accumulate experiences in the overhauling, welding, parts manufacturing, vehicle assembly, and testing of the M113 APC. In 1975, The Combined Logistics Command carried out the "Wan Cheng Program" (萬乘計劃), to domestically produce three M113 hulls using the aluminum alloy plates produced by the Taiwan Aluminum Corporation (known today as the Chinese Steel Aluminum Corporation).

The Wan Cheng 1 was an imitation of the M106 mortar carrier, but the 4.2 inch rifled mortar was replaced with a larger Type 63 120 mm smoothbore mortar, and this innovation later became the CM-22 howitzer carrier. The Wan Cheng 2 is an attempt to create a light tank by moving the engine to the rear and lowering the front half of the hull to accommodate a M24 turret while keeping the vehicle from being top-heavy. The Wan Cheng 3 had mounted a "Worker Bees IV MLRS" (工蜂四型多管火箭), a Multiple Launch Rocket System (MLRS). The MLRS was later mounted on six more US made M113s. (An unrelated Wan Cheng 4 project involves one M48A1 tank re-fitted into a M48A5).[3]

The Wan Cheng Program provided a solid foundation for the design, manufacture and development of the CM-21 armoured vehicle.

The standard version of CM-21 is an armoured personnel carrier (APC) that can carry up to 12 soldiers. It is largely the same as the basic M113 and inherits the same engine and transmission from the source design, but the welded aluminum alloy hull armour is further augmented with spaced armour at the front and the sides, the cavity within the spaced armour being filled with polyurethane to absorb the energy of incoming projectiles.

Overall, the CM-21 is better protected than the M113, but the CM-21 is 400 kilograms (880 pounds) heavier than the M113 and has slightly inferior mobility.

There are two firing ports on each side of the hull and one at the rear. Therefore, soldiers are sitting face to face in the front of the passenger compartment, and back to back in the rear. The CM-21 has floating capability, meaning it is able to cross water that is up to 1.5 metres (4.9 feet) deep without preparation. There are two water pumps that are switched on to lower the front flap. It is propelled by its tracks while in water.

Just like the M113, the CM-21 can also have external fuel tanks mounted on the rear. The basic armament of the CM-21 is one M2 Browning[4] machine gun or an Mk 19 automatic grenade launcher, and a quad-mounted smoke grenade launcher on both sides of the front.

A CM-21 is able carrying an M2 and an Mk 19 at the same time by using a bi-mounted gun rack.