3" Gun Motor Carriage M91-4

M9: General
Manufacturer Baldwin Locomotive Works Crew 5 men
M9: Dimensions
Combat weight 53,150lbs
24,110kg		 Height 92"
230cm
Length without gun 223.75"
568.33cm		 Width 107.375"
272.733cm
Tread 83"
211cm		 Ground clearance 19"
48cm
Ground pressure 11.3psi
.793kg/cm²
M9: Armament
Type Mount Ammunition Traverse Elevation
3" Gun M1918 Mount in hull center 40 rounds 37°
(10° left and 27° right;
manual)		 +29° to -8°
(manual)
Aiming equipment
Telescope M6 for gunner
M9: Armor
Assembly
Riveting
Hull
Rolled homogeneous steel
Location Thickness
Front 2.0"
5.1cm
Sides 1"
2.5cm
Rear .75"
1.9cm
M9: Automotive
Engine Wright (Continental) R975 EC1; 9 cylinder, 4 cycle, static radial, supercharged gasoline
Horsepower 360 Fuel capacity 174gal
659L
Transmission Synchromesh, 5 speeds forward, 1 reverse
Steering Controlled differential, steering levers
Brakes Mechanical, external contracting
M9: Suspension
Type Road wheels Track return rollers
Vertical volute spring 3 bogies/track;
2 wheels/bogie		 1 on top of each bogie
Drive sprockets Idlers Shock absorbers
13-tooth front drive Adjustable at rear of track None
M9: Track
T41
Outside guide, double pin, smooth, rubber
Width 16.0"
40.6cm		 Pitch 6"
15cm		 Shoes/track 79 Ground contact length 147"
373cm
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
M9: Performance
Max level road speed 25+mph
40+kph		 Max trench 74"
190cm
Max grade 30° Max vertical obstacle 24"
61cm
Max fording depth 25.25"
64.14cm		 Radius of action 180mi, road
290km, road

The 3" GMC M9 was based on the automotive components of the medium tank M3, and the superstructure was redesigned to form an open-topped octagonal firing position for the 3" antiaircraft gun M1918. The gun's traversing base ring was placed on a platform above the tank's propeller shaft, and the ordnance fired to the front of the vehicle. The driver sat to the left of the gun, limiting its traverse in that direction compared with to the right. The pilot had no aiming device for the ordnance, but on 13 March 1942 the telescope M6 in the telescope mount T42 was suggested for production vehicles. The Ordnance Department obtained permission to mount 50 M1918s on these carriages, and the vehicle was classified as substitute standard in April 1942. It turned out that only 27 of the guns were actually available, though. With the Tank Destroyer Board indicating its dislike for the M9, and with progress on the 3" GMC M10 well underway, the M9 was cancelled in August 1942 before production had commenced.

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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. Moran, Nicholas. Can Openers: The Development of American Anti-Tank Gun Motor Carriages. Brattleboro, VT: Echo Point Books & Media, 2017.
  3. Crismon, Fred W. U.S. Military Tracked Vehicles. Osceola, WI: Motorbooks International, 1992.
  4. Tank Data, vol. 3. Aberdeen Proving Ground, MD: US Army Ordnance School, Jul 1958.
Last updated 20 Dec 2023.
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© Copyright 2014 Chris Conners