The M19 used the M24 Light Tank chassis. It was to replace the Combination Gun Motor Carriage M15A1 to protect motor columns against aircraft.
Standardized in June 1944.
40 mm gun's AP shell had velocity of 2,870 ft/sec, range of 9,475 and could penetrate 1.6" at 1,000 yards. HE shell had velocity of 2,870, range of 10,820 yards, and ceiling of 7,625 yards. Could be fired at 240 rounds/minute, and traversed up to 40° per second.