M8: General | |||
Date of introduction | September 1942 | Total acceptances | 1,778 |
Manufacturer | Cadillac Motor Car Division of General Motors | Crew |
|
M8: Dimensions | |||
Combat weight | 34,600lbs 15,700kg |
Height over AAMG | 107" 272cm |
Length with sandshields | 196" 498cm |
Howitzer overhang forward | 0" |
Width with sandshields | 91.5" 232cm |
Tread | 73.5" 187cm |
Ground clearance | 14" 36cm |
Fire height | 76" 190cm |
Turret ring diameter | 54.4" 138cm |
Ground pressure, zero penetration | 12.5psi .878kg/cm² |
M8: Armament | ||||
Type | Mount | Ammunition | Traverse | Elevation |
75mm Howitzer M2 or M3 | M7 in turret | 46 rounds (6 ready) |
360° (manual) |
+40° to -20° (manual) |
.50cal M2HB MG | Concentric ring mount D60258 in turret | 400 rounds | 360° (manual) |
+85° to -13° (manual) |
Aiming equipment | ||||
Telescope M56, M56A1, or M70C; panoramic telescope M12A5 for gunner |
M8: Armor | ||
Assembly | ||
Welding | ||
Hull | ||
Rolled homogeneous steel | ||
Location | Thickness | Angle from vertical |
Upper front | 1.125" 2.858cm |
45° |
Lower front | 1.75" 4.45cm |
18° |
Front sides | 1.125" 2.858cm |
0° |
Rear sides | 1.0" 2.5cm |
0° |
Upper rear | 1.0" 2.5cm |
50° |
Middle rear | 1.0" 2.5cm |
0° |
Lower rear | 1.0" 2.5cm |
17° |
Top | .5" 1.3cm |
90° |
Front floor | .5" 1.3cm |
90° |
Rear floor | .375" .953cm |
90° |
Turret | ||
Rolled homogeneous steel | ||
Location | Thickness | Angle from vertical |
Howitzer shield (cast) | 1.5" 3.8cm |
0° to 60° |
Front | 1.5" 3.8cm |
0° to 63° |
Sides | 1.0" 2.5cm |
20° |
Rear | 1.0" 2.5cm |
20° |
Top | Open |
M8: Automotive | |||||
Engine | Twin Cadillac Series 42; 16 cylinder (8/engine), 4 cycle, 90° vee gasoline | ||||
Horsepower | Net: 220@3,400rpm (110/engine) Gross: 295@3,200rpm (148/engine) |
Torque | Net: 488 ft-lb@1,200rpm (244/engine) Gross: 560 ft-lb@ 1,200rpm (260/engine) |
Fuel capacity | 89gal 340L |
Transmission | Twin Hydramatic, 4 speeds forward, 1 reverse | ||||
Steering | Controlled differential, steering levers | ||||
Brakes | Mechanical, external contracting |
M8: Suspension | ||
Type | Road wheels | Track return rollers |
Vertical volute spring | 2 bogies/track; 2 wheels/bogie |
3/track |
Drive sprockets | Idlers | Shock absorbers | 13-tooth front drive | Trailing adjustable with volute spring at rear of track | None |
M8: Track | |||||||
T16E1 | |||||||
Outside guide, rubber bushed, double pin, reversible rubber | |||||||
Width | 11.6" 29.5cm |
Pitch | 5.5" 14cm |
Shoes/track | 66 | Ground contact length | 119" 302cm |
T16E2 | |||||||
Outside guide, rubber bushed, double pin, non-reversible rubber | |||||||
Width | 11.6" 29.5cm |
Pitch | 5.5" 14cm |
Shoes/track | 66 | Ground contact length | 119" 302cm |
T36E6 | |||||||
Outside guide, rubber bushed, double pin, steel, parallel grouser | |||||||
Width | 11.6" 29.5cm |
Pitch | 5.5" 14cm |
Shoes/track | 66 | Ground contact length | 119" 302cm |
T55E1 | |||||||
Outside guide, rubber bushed, double pin, steel, chevron | |||||||
Width | 11.6" 29.5cm |
Pitch | 5.5" 14cm |
Shoes/track | 66 | Ground contact length | 119" 302cm |
M8: Performance | |||
Max level road speed | 36mph 58kph |
Max trench | 64" 160cm |
Max grade | 60% | Max vertical obstacle | 18" 46cm |
Min turning diameter | 42' 13m |
Max fording depth | 36" 91cm |
Cruising range | ~100mi, roads ~160km, roads |
The 75mm HMC M8 was based on the light tank M5, but the front hull was modified by deletion of the drivers' hull roof hatches since the drivers had access to the vehicle through the open turret. Instead, the drivers each had a large door in the hull front plate for direct vision and two periscopes in the hull roof. The M7 howitzer mount incorporated parts of the medium tank M4's M34 gun mount. The 75mm howitzer M2 was an adaptation of the 75mm pack howitzer M1 and M1A1 that featured a howitzer tube mounting support over the howitzer tube. The 75mm howitzer M3 had the recoil surface and keyway machined directly onto the howitzer tube and therefore did not require a barrel support sleeve. Both howitzers used the same breech, and a large flash suppressor was fitted around the howitzer on the M8. Late-model M8s were armed with the M3 howitzer, equipped with sandshields around the tracks, and they stored track grousers on the turret.
The mounted positions of the crew differed from the action positions listed above. For travel, the chief rode in right side of the turret, the loader occupied the .50cal ring mount, and the gunner sat in the assistant driver's position.