The M19 Twin 40mm (M19 Gun Motor Carriage) self-propelled anti-aircraft system was developed towards the tail-end of World War 2 and made available in April of 1945. However, the war in Europe more-or-less ended the following month and the Empire of Japan capitulated in August of that same year, ending the war in the Pacific. As such, only three-hundred total M19 systems were delivered from the 904 that were initially ordered. The series would continue to serve in the post-war world and see service into the 1950s with the United States Army.
Design and Development
The M19 was developed to provide the US Army with a mobile, self-propelled, medium-class, anti-aircraft artillery system. The system in question would supply a defensive measure against low-flying enemy aircraft, protecting US Army motor columns in transit. The system was to be tracked in nature, allowing for some level of high mobility through those hard-to-traverse off road locales while still keeping up with motor columns on road. To speed along both development and production, the chassis of the M24 Chaffee light tank was selected as the starting point. The Chaffee hull was lengthened to an extent and had its engine placement relocated to the area behind the driver's position. Essentially, the engine compartment now divided the forward hull from the rear. The driver would control the vehicle via steering levers. In all, six personnel made up the crew complement of the M19 including the driver, an assistant driver (seated in the forward hull with the driver), two gunners seated side-by-side in the turret and two loaders seated side-by-side in the turret. Hull construction was of welded rolled homogenous steel offering armor protection levels up to 0.5-inches thick along the critical facings and less along the rear top. The turret was also of rolled homogenous steel with armor protection ranging from 0.25-inches thick along the sides of the gun shield to 0.5-inches along the front of the gun shield. The M19 was standardized in June of 1944 and orders for several hundred systems were placed by August of 1944 with production slated to begin in April of 1945. The M19 was intended to replace the Combination Gun Motor Carriage M15A1 series.
The rear of the hull was occupied by a power-operated, 360-degree traversing open-air turret system mounting a pair of 40mm M2 Dual Automatic Guns (essentially Bofors 40mm antiaircraft cannons in the US Army inventory) in an M4 mounting. The turret featured an elevation function of +85-degrees to -3-degrees using manual and hydraulic means (covering 40-degrees per second). The weapon systems were tied to the M13 or M13A1 fitting the M23 or M24 reflex sights. Each 40mm cannon was fed via a clip containing the 40mm ammunition and operated by way of an automatic loader. Each clip held four rounds while the automatic loader had room for seven. The barrels were rated to fire up to 120 rounds-per-minute. Three hundred fifty-two 40mm projectiles were carried aboard the M19 itself while a further 320 rounds could be accessed through use of a special towed M28 trailer.
The M2 made use of a 40mm AP (Armor-Piercing) or a 40mm HE (High-Explosive) shell with a muzzle velocity of 2,870 feet per second. The AP had a range out to 9,475 yards while the HE had a range out to 10,820 yards. Vertical range was limited to 7,625 yards.
Tracks and Suspension
The M19 sat on either the T72 or T85E1 series track with a width of 16- or 14-inches respectively. Suspension was of the torsion bar variety making use of five individually sprung road wheels to a track side. There was a drive sprocket fitted to the front with the idler at the rear. Four track return rollers were used. Shock absorbers were located along the first two and last two wheels on each respective track side.
Powerplant and Performance
Power was derived from a pair of Cadillac Series 44T4 16-cylinder, 4-cycle, 90-degree Vee gasoline engine delivering 110 horsepower at 3,400rpm. The powerplant was tied to a Twin Hydraulic transmission system featuring eight forward speeds and four reverse speeds. This provided for a road speed of 35 miles per hour with a road range of approximately 100 miles off of the internal 110-gallon fuel tank. Maximum grade traversing was rated at 60% while trenches up to 108-inches could be conquered. Maximum vertical obstacle height was 40-inches while fording depth was limited to 42-inches.
The Improved M19A1
The M19 was revised with the addition of a 200-amp auxiliary engine-driven generator (situated on the right fender) to become the M19A1. Additionally, some of the communications equipment was moved to blister positions along the turret. A visually differentiating feature between the M19 and M19A1 became her different exhaust pipes. The M19 featured these as two units running around each side of the front of the turret while the M19A1 sported both of these pipes along the left side of the vehicle. In all, however, the M19A1 differed only slightly in overall design when compared to her predecessor.
Cadillac Motor Car Division of General Motors Corporation headed up all production of the M19 series for the US Army.