155mm Gun Motor Carriage M401-8

M40: General
Date of first acceptance February 1945 Total acceptances 418
(24 converted to 8" HMC M43)
Manufacturer Pressed Steel Car Co. Crew 8 men
M40: Dimensions
Combat weight 81,000lbs
37,000kg		 Height over gun mount 130"
330cm
Length without gun 280.4"
712.2cm		 Gun overhang forward 68"
170cm
Width 124"
315cm		 Tread 101"
257cm
Ground clearance 17"
43cm		 Fire height 102"
259cm
Ground pressure, zero penetration 10.7psi
.751kg/cm²
M40: Armament
Type Mount Ammunition Traverse Elevation
155mm Gun M1A1 or M2 M13 on rear of chassis 20 rounds 36°
(18° left and right;
manual)		 +45° to -5°
(manual)
Aiming equipment
Panoramic telescope M12 or M12A7C and telescope M69F for gunner; elbow telescope M16A1F for cannoneer no.1
M40: Armor
Assembly
Welding
Hull
Rolled and cast homogeneous steel
Location Thickness Angle from vertical
Upper front .5"
1.3cm		 58°
Lower front 4.25" to 2.0"
10.8cm to 5.1cm		 0° to 46°
Upper sides .5"
1.3cm		 0°
Lower sides 1.0"
2.5cm		 0°
Rear .5"
1.3cm		 0°
Top .5"
1.3cm		 85°
Front floor 1.0"
2.5cm		 90°
Rear floor .5"
1.3cm		 90°
Gun shield .5"
1.3cm		 ~45°
M40: Automotive
Engine Continental R975 C4; 9 cylinder, 4 cycle, static radial, supercharged gasoline
Horsepower Net: 400@2,400rpm
Gross: 460@2,400rpm		 Torque Net: 940 ft-lb@1,700rpm
Gross: 1025 ft-lb@1,800rpm		 Fuel capacity 215gal
814L
Transmission Synchromesh, 5 speeds forward, 1 reverse
Steering Controlled differential, steering levers
Brakes Mechanical, external contracting
M40: Suspension
Type Road wheels Track return rollers
Horizontal volute spring 3 bogies/track;
2 dual wheels/bogie		 2 dual/track, 3 single/track
Drive sprockets Idlers Shock absorbers
13-tooth front drive Dual adjustable at rear of track One on each bogie
M40: Track
T66
Center guide, single pin, cast, steel
Width 23"
58cm		 Pitch 6"
15cm		 Shoes/track 86 Ground contact length 164"
417cm
T80
Center guide, double pin, rubber and steel
Width 23"
58cm		 Pitch 6"
15cm		 Shoes/track 86 Ground contact length 164"
417cm
T84
Center guide, double pin, rubber
Width 23"
58cm		 Pitch 6"
15cm		 Shoes/track 86 Ground contact length 164"
417cm
M40: Performance
Max level road speed 21mph sustained
24mph dash
34kph sustained
39kph dash		 Max trench 92"
230cm
Max grade 60% Max vertical obstacle 24"
61cm
Min turning diameter 83'
25m		 Max fording depth 40"
102cm
Cruising range ~100mi, roads
~160km, roads

The hull and chassis of the M40 were based on that of the late-production medium tank M4. The hull was lengthened and widened and used HVS suspension. The drivers were provided with individual viewing cupolas. The layout of the M40 was similar to the 155mm GMC M12 in that the engine was moved forward to behind the driving compartment, the gun was mounted at the rear of the vehicle, and the M40 was open-topped except for the driving compartment.

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References

  1. Hunnicutt, R.P. Sherman: A History of the American Medium Tank. Navato, CA: Presidio Press, 1994. Reprinted with permission from Sherman, R.P. Hunnicutt ©1994, available from Presidio Press, 505B San Martin Drive, Suite 160, Navato, CA 94945.
  2. Doyle, David. M40 Gun Motor Carriage and M43 Howitzer Motor Carriage in WWII and Korea. Atglen, PA: Schiffer Publishing, Ltd., 2017.
  3. TM 9-747 155-mm Gun Motor Carriage T83 and 8-inch Howitzer Motor Carriage T89. Washington, DC: War Department, 26 February 1945.
  4. TM 9-747 155-mm Gun Motor Carriage M40 and 8-inch Howitzer Motor Carriage M43. Washington, DC: War Department, 15 September 1947.
  5. TM 9-1747 Ordnance Maintenance--155-mm Gun Motor Carriage M40 and 8-in. Howitzer Motor Carriage M43 Hull and Suspension. Washington, DC: Department of the Army, 21 October 1947.
  6. ORD 9 SNL G-232 List of All Service Parts for Carriage, Motor, 155-mm Gun, M40 and Carriage, Motor, 8-in Howitzer, M43. Washington, DC: Department of the Army, October 1952.
  7. Chamberlain, Peter, and Chris Ellis. British and American Tanks of World War Two. Frome, England: Cassell & Co., 2000.
  8. Siemers, Cary. "USA's Self Propelled Guns." World War II Tanks & Vehicles and Advanced Squad Leader. 4 Feb 2001. 8 Feb 2001 <http://www.shadowsfolly.com/WWII/USA/SelfPropelled.htm>.
Last updated 21 Jan 2024.
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© Copyright 2001-24 Chris Conners