4.2" Self-propelled Mortar M841-4

M84: General
Date of first acceptance 1957
Manufacturer FMC Corp. Crew
6 men:
  • Commander in hull right front
  • Gunner in hull rear
  • Driver in hull left front
  • Loader in hull rear
  • 2 ammunition handlers in hull rear
M84: Dimensions
Combat weight 47,100lbs
21,400kg		 Height over cupola 109.0"
276.9cm
Length 221.0"
561.3cm		 Width over track shrouds 128.5"
326.4cm
Tread 103.0"
261.6cm		 Ground clearance 18.0"
45.7cm
Ground pressure, zero penetration 9.2psi
.65kg/cm²
M84: Armament
Type Mount Ammunition Traverse Elevation
4.2" Mortar M30 8731738 in rear hull;
Ground Mount M24A1 stowed on rear hull		 88 rounds 50°
(25° left and right;
manual)		 +45° to +59°
(manual)
.50cal TTHB MG M13 cupola 2,205 rounds 360°
(manual)		 Manual
Aiming equipment
Sightunit M34A2 for gunner, periscope sight M28 for commander
Night vision
Infrared periscope M19 for driver
M84: Armor
Assembly
Welding
Hull
Rolled and cast homogeneous steel
Location Thickness Angle from vertical
Upper front .625"
1.59cm		 50°
Middle front .625"
1.59cm		 0°
Lower front .625"
1.59cm		 55°
Sides .625"
1.59cm		 0°
Rear .625"
1.59cm		 7°
Top .375"
.953cm		 90°
Floor 1.0"
2.5cm		 90°
M84: Automotive
Engine Twin GMC Model 302; 6 cylinder, 4 cycle, inline gasoline
Horsepower Net: 254@3,350rpm
(127/engine)
Gross: 292@3,600rpm
(146/engine)		 Torque Net: 508 ft-lb@1,800rpm
(254/engine)
Gross: 530 ft-lb@1,800rpm
(265/engine)		 Fuel capacity 135gal
511L
Transmission Twin Hydramatic Model 301MG, 4 speeds forward, 1 reverse
Steering Controlled differential, steering levers
M84: Suspension
Type Road wheels Track return rollers
Torsion bar 5 individually sprung dual/track 3 dual/track
Drive sprockets Idlers Shock absorbers
12-tooth front drive Dual compensating at rear of track On first and last road wheels/track
M84: Track
T91E3
Center guide, single pin, steel with detachable rubber pad
Width 21"
53cm		 Pitch 6"
15cm		 Shoes/track 72 Ground contact length 121.25"
307.98cm
M84: Performance
Max level road speed 27mph
43kph		 Max water speed 3.5mph
5.6kph
Max trench 66"
170cm		 Max grade 60%
Max vertical obstacle 18"
46cm		 Min turning diameter 30'
9.1m
Max fording depth Floats Cruising range ~100mi, roads
~160km, roads

The M84 mortar carrier was based on the M59 armored personnel carrier. The mortar was mounted in the passenger compartment, facing the rear, and the rear roof hatches were reconfigured to include front, center, and rear hinged hatches, all of which folded to the front when the mortar was in use. The escape hatch in the rear ramp was relocated from the left to the right side, and the mortar ground mount was then stowed on the left of the ramp. Because it weighed substantially more than the M59, the M84's air intake and exhaust grilles were provided with collapsible snorkels for use when swimming.

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References

  1. Hunnicutt, R.P. Bradley: A History of American Fighting and Support Vehicles. Navato, CA: Presidio Press, 1999. Reprinted with permission from Bradley, R.P. Hunnicutt ©1999, available from Presidio Press, 505B San Martin Drive, Suite 160, Navato, CA 94945.
  2. TM 9-2300-203-12 Operation and Organizational Maintenance: Full Tracked Armored Personnel Carrier M59 (T59) and 4.2-inch Full Tracked Self-propelled Mortar M84. Washington, DC: Headquarters, Dept. of the Army, 25 Oct 1958.
  3. ORD 9 SNL G-280 List of All Service Parts of Infantry Vehicle, Armored, Tracked, M59 (T59). Washington, DC: Department of the Army, 28 September 1954.
  4. Crismon, Fred W. U.S. Military Tracked Vehicles. Osceola, WI: Motorbooks International, 1992.
Last updated 16 Jan 2024.
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© Copyright 2001-24 Chris Conners