Staff Writer (Updated: 7/1/2014):
Development of the M163 coincided with the development of the US Army's other air defense project - the missile-minded MIM-72A/M48 "Chaparral". The Chaparral system was also built atop the tracked M113 chassis and featured a forward-set cab for its operating crew and a positional, four-missile launch system mounting a surface-to-air version of the air-to-air AIM-9 Sidewinder short-ranged missile. The Chaparral served from 1969 to 1998 and nearly 2,000 examples were produced. The M163 Vulcan would be fielded alongside the M48 Chaparral to complete the network by providing a potent short-ranged "one-two" punch utilizing both homing missiles and voluminous fire.
The strong arm of the M163 Vulcan air defense system was its installation of the M61 Vulcan cannon. The rotary cannon was 20mm in caliber and fitted to a powered turret offering 360-degree traverse. Elevation was limited to +80 and -5 and effective range was out to 5 kilometers depending on ammunition type. The cannon could be set to fire at a high rate-of-fire at 3,000 rounds per minute or low at 1,000 rounds per minute in 10, 30, 60 or 100 round bursts. The feed system of linkless in nature. Ammunition variety was key to the success of the M163 and differing types were eventually offered. This included Armored Piercing Incendiary, High-Explosive Incendiary, HEI-T, MPT-SD, SAPHEI and APDS type rounds.
Beyond the installation of the gun, the chassis of the M113 remained largely intact for the M163. The design was characterized by its slab sides, sloped front glacis plate and squared off rear section. The turret was mounted at the middle-center of the hull roof. A pair of tracks straddled the hull sides and featured five rubber-tired road wheels with the drive sprocket at the front hull and the track idler at the rear. A crew of four was the operating ground and included the driver, seated at front left, the commander, gunner and loader. The rear loading ramp from the M113 was also retained. The powerplant, seated in the front hull, is a General Motors 6V53 series 6-cylinder 2-cycle diesel engine developing 212 horsepower @ 2,800rpm.