Howitzer Motor Carriage M8

The 75 mm Howitzer Motor Carriage M8 was a self-propelled howitzer vehicle of the United States in use during World War II.[2] It was developed on the chassis of the M5 Stuart tank and was equipped with a M116 howitzer in an M7 mount.

75 mm Howitzer Motor Carriage M8
75 mm Howitzer Motor Carriage M8 on display at the Musée des Blindés.
TypeSelf-propelled artillery
Place of originUnited States
Service history
In service1942-1960s
Used bySee Users
Wars
Production history
DesignerU.S. Army Ordnance Department
Designed1942
ManufacturerCadillac division of General Motors
ProducedSeptember 1942–January 1944
No. built1,778
VariantsM8, M8A1 (not produced)
Specifications (75 mm HMC M8[1])
Mass34,600 lb (15.4 long tons; 15.7 t) combat weight
Length16 ft 4 in (4.98 m) with sand shields
Width7 ft 7.5 in (2.324 m) with sand shields
Height8 ft 11 in (2.72 m) over anti-aircraft machine gun
Crew4 (Commander, gunner, driver, assistant driver/loader)
Armor0.374–1.75 in (9.5–44.5 mm)
Main
armament
75 mm Howitzer M2/M3 in Mount M7
46 rounds
Secondary
armament
.50 caliber (12.7 mm) Browning M2HB machine gun
400 rounds
EngineTwin Cadillac Series 42 inline 6 cylinder 4-stroke gasoline engine
220 hp (160 kW) total at 3,400 rpm
Power/weight14.02 hp (10.45 kW)/metric ton
TransmissionTwin Hydramatic, 4 speeds forward, 1 reverse
SuspensionVertical volute spring suspension (VVSS)
Ground clearance14 in (360 mm)
Fuel capacity89 US gal (340 l)
Operational
range
100 mi (160 km) on road
Maximum speed 36 mph (58 km/h) on road
Steering
system
Controlled differential, steering levers

Development and design

The first design for a close support howitzer on an M5 tank chassis was the T41, which had the howitzer in the hull front. This did not progress past the mock-up stage as the crew would not have been sufficiently protected and design work started on the T47.[3] It was developed on the chassis of the then-new Light Tank M5 (Stuart VI). The prototype was designated the 75 mm Howitzer Motor Carriage T17E1[4] It had the standard M5 turret removed and replaced with a larger open-topped turret; as a result, the drivers' hatches had to be moved from the hull roof to the glacis plate. After a mock-up had been produced, it was ordered into production as the 75 mm Howitzer Motor Carriage M8. The M8 was based upon the Light Tank M5, but incorporated several changes. Like the Light Tank M5, the M8 had a crew of four; commander, gunner, driver, and assistant driver/loader. When the M8 was in action, the commander positioned himself at the antiaircraft machine gun and directed his crew, the gunner sat in the turret on the right side of the howitzer, the assistant driver/loader moved up from his seat in the right front hull, and the driver stayed at his position.[5]

Due to the usage of a new turret, the crew hatches in the hull roof for the driver and assistant driver/loader were removed and replaced by a pair of vision flaps in the glacis. Since the glacis hatches were too small to disembark through, these two crew members had to leave the vehicle through the open-topped turret. The driver and assistant driver/loader were provided with periscopes for visibility. In November 1944, the Ordnance Department gave the M8 the name General Scott, after American general Winfield Scott.

Armor

The M8 was based upon the Light Tank M5 (itself a descendant of the Light Tank M3) it had relatively thin armor. The lower hull armor ranged from 1 in (25 mm) to 1.125 in (28.6 mm) on the sides to 1.75 in (44 mm) on the lower front and 1.0 in (25 mm) on the lower rear. The lower hull sides were vertical, while the lower hull front was sloped at 18 degrees from the vertical, and the lower hull rear, which protected the engine and radiator, was sloped at 17 degrees from the vertical. The hull floor ranged from 0.5 in (13 mm) thick at the front to 0.375 in (9.5 mm) thick at the rear. The glacis plate of the M8 was sloped at 45 degrees from the vertical and was 1.125 in (28.6 mm) thick. The upper hull sides, like the lower hull sides, were vertical and 1.125 in (28.6 mm) thick at the front, thinning to 1 in (25 mm) thick at the rear. The upper rear hull was a vertical plate, 1 in (25 mm). The plate sloped at 50 degrees for a short distance before it met the hull roof, which was uniformly 0.5 in (13 mm) thick, and flat.

The turret of the M8 was of cast steel. It was 1.5 in (38 mm) thick at the front, which was rounded, sloping from 0 to 63 degrees from the vertical. The sides and rear were 1 in (25 mm) thick and sloped at 20 degrees from the vertical. The cast gun shield, which covered the barrel of the 75 mm Howitzer M2/M3, was 1.5 in (38 mm) thick and rounded.

Armament

The armament of the M8 consisted of a new open-topped turret armed with a 75 mm M2 howitzer, later a 75 mm M3 howitzer. The M8 carried 46 rounds of 75 mm ammunition; 11 rounds at the right rear of the fighting compartment, 20 rounds at the left rear of the fighting compartment, 9 rounds in the left hull sponson, and 6 "ready" rounds stored between the driver and assistant driver's positions. The most common types of ammunition carried were the M89 white phosphorus shell and the M48 high explosive shell. Unlike the standard M5 light tank, the M8 featured no hull-mounted or coaxial Browning M1919A4 .30 caliber machine gun. A Browning M2HB .50 caliber machine gun with 400 rounds was mounted on the right rear corner of the turret for local defense and anti-aircraft purposes. For self-defense, the vehicle driver was provided with a Thompson submachine gun, while the other three crew members were issued M1 carbines.[6]

Production

1,778 of the Howitzer Motor Carriage M8 were produced by the Cadillac division of General Motors from September 1942 to January 1944.

Production of M8 Howitzer Motor Carriage[7][8]
Month Number built Serial number(s) Registration number(s)
September 1942 1 1 4051234
October 1942 24 2-25 4051235-4051258
November 1942 101 26-126 4051259-4051359
December 1942 247 127-373 4051360-4051606
January 1943 160 374-533 4051607-4051766
February 1943 160 534-693 4051767-4051927
March 1943 160 694-853 4051928-4052086
April 1943 160 854-1013 4052087-4052246
May 1943 160 1014-1173 4052247-4052406
June 1943 160 1174-1333 4052407-4052566
July 1943 62 1334-1395 4052567-4052628
August 1943 62 1396-1457 4052629-4052690
September 1943 62 1458-1519 4052691-4052752
October 1943 62 1520-1581 4052753-4052814
November 1943 62 1582-1643 4052815-4052876
December 1943 60 1644-1703 4052877-4052938
January 1944 75 1704-1778 4052939-4053011
Total 1,778

Combat service

M8's were issued to Headquarters companies in medium tank battalions in Europe. Starting in 1944 they were replaced by the 105mm howitzer variant of the M4 Sherman tank.[9] The 75 mm Howitzer Motor Carriage M8 was assigned to the Assault Gun Troops of Cavalry Reconnaissance Squadrons in order to give them close support against enemy fortified positions.[10][11] The high elevation (40 degrees) of the howitzer was useful for hitting enemies emplaced on the sides of hills. The M8 was used in the Italian Campaign, the Western Front, and in the Pacific Theater by the US Army and on the Western Front by the French Army. It was also used by the French Union and State of Vietnam during the First Indochina War. It stayed in French service until the 1960s and saw service in Algeria. Nine M8s were also used by the partisans in Yugoslavia under the name Kadilak.[12]

Variants
  • 75 mm Gun Motor Carriage M8A1: A lightweight tank destroyer prototype that used an M5A1 light tank hull. The M8's turret was paired with a 75 mm gun M3 as used on the M4 Sherman tank. The project was later cancelled with the development of the M18 Hellcat.

Users

See also

References
  1. Conners, Chris. "75mm HMC M8". afvdb.50megs.com.
  2. "M8 Scott (Howitzer Motor Carriage M8) 75mm Self-Propelled Howitzer (SPH) (1942)". MilitaryFactory. October 17, 2014. Retrieved February 5, 2015.
  3. Chamberlain and Ellis (1969) British and American Tanks of World War II p96
  4. "United States' T Number Designations - World War II Vehicles". www.wwiivehicles.com.
  5. War Department Armored Command Field Manual 17-69 Crew Drill, Service of the Piece, and Gunnery (75-MM Assault Howitzer on Motor Carriage M8), dated 30 November 1943, pp. 3-5
  6. War Department Armored Command Field Manual 17-69 Crew Drill, Service of the Piece, and Gunnery (75-MM Assault Howitzer on Motor Carriage M8), dated 30 November 1943, p.4
  7. Ordnance Department Armored, Tank, and Combat Vehicles 1940-45, page 11 (1 May 1945)
  8. Official Munitions Production of the United States by Months, July 1, 1940 - August 1, 1945, page 231 (War Production Board and Civilian Production Administration, 1 May 1947)
  9. Chamberlain & Ellis p97
  10. "Table of Organization and Equipment No. 2-25. War Department, Washington 25, D.C., 15 September 1943 (Cavalry Reconnaissance Squadron, Mechanized)" (PDF). Retrieved 16 August 2017.
  11. "Table of Organization and Equipment No. 2-28. War Department, Washington 25, D.C., 15 September 1943 (Cavalry Assault Gun Troop, Mechanized)" (PDF). Retrieved 16 August 2017.
  12. German and Allied Armour in Yugoslavia in World War Two.
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