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M7
M7B1


105mm Howitzer Motor Carriage M71-7
M7: General
Date of introduction April 1942 Total acceptances 3490
Manufacturers
  • American Locomotive Co.
  • Federal Machine and Welder Co.
Crew
7 men:
  • Chief of section in hull left front
  • Gunner-corporal in hull left center
  • Cannoneer in hull right front
  • Cannoneer in hull left rear
  • Cannoneer in hull right center
  • Cannoneer in hull right rear
  • Driver in hull left front
M7: Dimensions
Combat weight 50,600lbs
23,000kg
Height over AAMG 116"
295cm
Length with sandshields 237"
602cm
Howitzer overhang forward with sandshields 0"
Width with sandshields 113"
287cm
Tread 83"
211cm
Ground clearance 17"
43cm
Fire height 76"
190cm
Ground pressure, zero penetration 10.4psi
.730kg/cm²
M7: Armament
Type Mount Ammunition Traverse Elevation
105mm Howitzer M2A1 M4 in hull right front 69 rounds 45°
(15° left and 30° right;
manual)
+35° to -5°
(manual)
.50cal M2HB MG Ring mount at hull right front 300 rounds 360°
(manual)
Manual
M7: Armor
Assembly
Welding
Hull
Rolled and cast homogeneous steel
Location Thickness Angle from vertical
Upper front .5"
1.3cm
30°
Lower front 4.25" to 2.0"
10.8cm to 5.1cm
0° to 56°
Upper sides .5"
1.3cm
Lower sides 1.5" (soft)
3.8cm (soft)
Rear .5"
1.3cm
Front floor 1.0"
2.5cm
90°
Rear floor .5"
1.3cm
90°
M7: Automotive
Engine Continental R975 C1; 9 cylinder, 4 cycle, radial gasoline
Horsepower Net: 350@2400rpm
Gross: 400@2400rpm
Torque Net: 800 ft-lb@1800rpm
Gross: 890 ft-lb@1800rpm
Fuel capacity 175gal
662L
Transmission Synchromesh, 5 speeds forward, 1 reverse
Steering Controlled differential, steering levers
Brakes Mechanical, external contracting
M7: Suspension
Type Road wheels Track return rollers
Vertical volute spring 3 bogies/track;
2 wheels/bogie
1 at rear of each bogie
Drive sprockets Idlers Shock absorbers
13-tooth front drive Adjustable at rear of track None
M7: Track
T48
Outside guide, double pin, chevron, rubber
Width 16.56"
42.06cm
Pitch 6"
15cm
Shoes/track 79 Ground contact length 147"
373cm
T49
Outside guide, double pin, parallel bar, steel
Width 16.56"
42.06cm
Pitch 6"
15cm
Shoes/track 79 Ground contact length 147"
373cm
T51
Outside guide, double pin, smooth, rubber
Width 16.56"
42.06cm
Pitch 6"
15cm
Shoes/track 79 Ground contact length 147"
373cm
T54E1
Outside guide, double pin, chevron, steel
Width 16.56"
42.06cm
Pitch 6"
15cm
Shoes/track 79 Ground contact length 147"
373cm
M7: Performance
Max level road speed 21mph sustained
24mph dash
34kph sustained
39kph dash
Max trench 90"
230cm
Max grade 60% Max vertical obstacle 24"
61cm
Min turning diameter 62'
19m
Max fording depth 40"
100cm
Cruising range ~120mi, roads
~190km, roads


The 105mm HMC M7 was designed on the chassis of the medium tank M3, whereby the upper hull and turret were removed and replaced with an open-topped superstructure with the 105mm howitzer in the right front corner, and the .50cal MG ring mount to the right of the howitzer. The pulpit-like appearance of the .50cal MG mount is what gave the M7 its nickname of Priest. Early models retained holdovers from the M3, namely the early-type bogies with the return roller on top, and the three-piece final drive and differential housing with a notch taken from the top right corner to make room for the M3's sponson-mounted 75mm gun. Later M7s used both single- and three-piece final drive and differential housings from the medium tank M4 Sherman as well as the later heavy-duty suspension bogies. Improvements to late-production M7s included hinged armor plates on the vehicles' sides that could swing up to protect previously exposed 105mm ammunition, and a new howitzer travel lock. Features originally seen on the medium tank M4 Sherman also appeared on later M7s, namely disc instead of spoked road and idler wheels, the single-piece sharp-nosed final drive and differential housing, and double-anchor brakes.

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105mm Howitzer Motor Carriage M7B12-8
M7B1: General
Date of introduction March 1944 Total acceptances 826
Manufacturer Pressed Steel Car Co. Crew
7 men:
  • Chief of section in hull left front
  • Gunner-corporal in hull left center
  • Cannoneer in hull right front
  • Cannoneer in hull left rear
  • Cannoneer in hull right center
  • Cannoneer in hull right rear
  • Driver in hull left front
M7B1: Dimensions
Combat weight 50,000lbs
22,700kg
Height over AAMG 116"
295cm
Length 243.75"
619.13cm
Howitzer overhang forward with sandshields 0"
Width with sandshields 113"
287cm
Tread 83"
211cm
Ground clearance 17"
43cm
Fire height 76"
190cm
Ground pressure, zero penetration 10.3psi
.723kg/cm²
M7B1: Armament
Type Mount Ammunition Traverse Elevation
105mm Howitzer M2A1 M4 in hull right front 69 rounds 45°
(15° left and 30° right;
manual)
+35° to -5°
(manual)
.50cal M2HB MG Ring mount at hull right front 300 rounds 360°
(manual)
Manual
M7B1: Armor
Assembly
Welding
Hull
Rolled and cast homogeneous steel
Location Thickness Angle from vertical
Upper front .5"
1.3cm
30°
Lower front 4.25" to 2.0"
10.8cm to 5.1cm
0° to 56°
Upper sides .5"
1.3cm
Lower sides 1.5" (soft)
3.8cm (soft)
Rear .5"
1.3cm
Front floor 1.0"
2.5cm
90°
Rear floor .5"
1.3cm
90°
M7B1: Automotive
Engine Ford GAA; 8 cylinder, 4 cycle, 60 vee gasoline
Horsepower Net: 450@2600rpm
Gross: 500@2600rpm
Torque Net: 950 ft-lb@2200rpm
Gross: 1040 ft-lb@2200rpm
Fuel capacity 168gal
636L
Transmission Synchromesh, 5 speeds forward, 1 reverse
Steering Controlled differential, steering levers
Brakes Mechanical, external contracting
M7B1: Suspension
Type Road wheels Track return rollers
Vertical volute spring 3 bogies/track;
2 wheels/bogie
1 at rear of each bogie
Drive sprockets Idlers Shock absorbers
13-tooth front drive Adjustable at rear of track None
M7B1: Track
T48
Outside guide, double pin, chevron, rubber
Width 16.56"
42.06cm
Pitch 6"
15cm
Shoes/track 79 Ground contact length 147"
373cm
T49
Outside guide, double pin, parallel bar, steel
Width 16.56"
42.06cm
Pitch 6"
15cm
Shoes/track 79 Ground contact length 147"
373cm
T51
Outside guide, double pin, smooth, rubber
Width 16.56"
42.06cm
Pitch 6"
15cm
Shoes/track 79 Ground contact length 147"
373cm
T54E1
Outside guide, double pin, chevron, steel
Width 16.56"
42.06cm
Pitch 6"
15cm
Shoes/track 79 Ground contact length 147"
373cm
M7B1: Performance
Max level road speed 26mph
42kph
Max trench 90"
230cm
Max grade 60% Max vertical obstacle 24"
61cm
Min turning diameter 62'
19m
Max fording depth 36"
91cm
Cruising range ~120mi, roads
~190km, roads


The M7B1 was based on the medium tank M4A3 Sherman, but was otherwise similar to the late-model M7.

M7B1s were modified during the Korean War by raising the howitzer mount, and consequently the height of the HMC as well, which increased the howitzer's maximum elevation to +65°. The .50cal MG ring mount was also raised to ensure the weapon had an unobstructed field of fire. M7B1s modified in this way were designated M7B2.


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References

  1. TM 9-731E Carriage, Motor, 105-mm Howitzer, M7. Washington, DC: War Department, 15 August 1944.

  2. FM 17-63 Service of the Piece, 105-mm Howitzer, Self-Propelled. Washington, DC: War Department, 18 August 1942.

  3. 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.

  4. Catalogue of Standard Ordnance Items, 2nd edition 1944, volume 1. Washington, DC: Office of the Chief of Ordnance Technical Division, 1 June 1945.
  5. TM 9-1325 Ordnance Maintenance--105-mm Howitzers M2 and M2A1; Carriages M2A1 and M2A1; and Combat Vehicle Mounts M3 and M4. Washington, DC: War Department, 21 September 1944.

  6. Chamberlain, Peter, and Chris Ellis. British and American Tanks of World War Two. Frome, England: Cassell & Co., 2000.

  7. Siemers, Cary. "USA's M7, M7B1, M37 105mm Self Propelled Howitzer." World War II Tanks & Vehicles and Advanced Squad Leader. 25 Nov 2000. 10 Jan 2001 <http://www.shadowsfolly.com/WWII/USA/M7_M37SelfPropelled.htm>.

  8. FM 6-74 105-mm Howitzer M2A1 on Motor Carriage M7B1 and M7B2. Washington, DC: Department of the Army, March 1954.



Last updated 6 Oct 2014.

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© Copyright 2001-14 Chris Conners