The first subject in this volume of the M113 and derivatives is the M163A2 VULCAN air defense artillery gun. The basic idea to fit the 20mm General Electric M168 cannon (used to date on jet aircraft such as the F-104 Starfighter and the F-16 with success) to a modified M113 tracked vehicle (actually the M741) emerged in with production beginning in 1967. Intended was a lightweight, self-propelled weapon for close-in defense against low-flying aircraft, in addition to be employed against ground targets. The gun was mounted inside a small protective turret (M157A1 mount) which in turn was fitted on top of the modified roof. Two floating cells to the sides and one on the bow vane compensated the heavy weight of turret and ammunition (some 2,130 rounds inside the nuin. enabling the M163 to remain amphibious. A special feature of the M741 chassis is the lock-out of the hydraulic suspension when emplaced, providing a stable gun platform. Although it can fire at a maximum high rate of 3000 rounds per minute it proved little successful against jets flying at speeds of 400 knots and more, painfully experienced by the first five M163's sent to Vietnam for test-shooting. Moreover, its fair-weather, daylight ranging radar system limited its deployment. The system proved more effective against ground targets, illustrated by the Israeli Army who extensively used the system in combat. ( )