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M109
M109A1
M109A2
M109A6 Paladin

155mm Self-propelled Howitzer M1091-10

M109: General
Date of first acceptance November 1962 Total acceptances 3,786
Manufacturers
  • Cadillac Motor Car Division of General Motors Corp.
  • Chrysler Corp.
  • Allison Division of General Motors Corp.
Crew
6 men:
  • Chief of section in cab right rear
  • Gunner in cab left front
  • Assistant gunner in cab right front
  • 2 cannoneers in cab
  • Driver in hull left front
M109: Dimensions
Combat weight 52,461lbs
23,796kg		 Height over AAMG 129.1"
327.9cm
Length without howitzer 240.7"
611.4cm		 Howitzer overhang forward 19.7"
50.0cm
Width without fenders 124.0"
315.0cm		 Tread 109.0"
276.9cm
Ground clearance 17.7"
45.0cm		 Fire height ~78"
~200cm
Turret ring diameter 100"
250cm		 Ground pressure, zero penetration 11.2psi
.779kg/cm²
M109: Armament
Type Mount Ammunition Traverse Max traverse rate Elevation Max elevation rate
155mm Howitzer M126 or M126A1 M127 in turret 28 rounds 360°
(manual and hydraulic)		 11°/sec +75° to -3°
(manual and hydraulic)		 7°/sec
.50cal M2HB MG Flexible in turret AA mount 500 rounds 360°
(manual)		 -- Manual --
Aiming equipment
Panoramic telescope M117 for gunner and telescope M118C for assistant gunner
M109: Armor
Assembly
Welding
Hull
Rolled 5083 aluminum alloy
Location Thickness Angle from vertical
Upper front 1.25"
3.18cm		 75°
Lower front 1.25"
3.18cm		 19° and 60°
Sides 1.25"
3.18cm		 0°
Rear 1.25"
3.18cm		 0°
Top 1.25"
3.18cm		 90°
Floor 1.25"
3.18cm		 90°
Turret
Rolled 5083 aluminum alloy
Location Thickness Angle from vertical
Front 1.25"
3.18cm		 22°
Sides 1.25"
3.18cm		 22°
Rear 1.25"
3.18cm		 0°
Top 1.25"
3.18cm		 90°
M109: Automotive
Engine General Motors 8V71T; 8 cylinder, 2 cycle, vee, supercharged diesel
Horsepower Net: 345@2,300rpm
Gross: 405@2,300rpm		 Torque Net: 895 ft-lb@1,600rpm
Gross: 980 ft-lb@1,700rpm		 Fuel capacity 135gal
511L
Transmission Allison XTG-411-2A, 4 ranges forward, 2 reverse
Steering Mechanical, steering wheel (clutch-brake in 1st, 2nd, 1st reverse; geared steer in 3rd, 4th, 2nd reverse)
Brakes Multiple disc
M109: Suspension
Type Road wheels Track return rollers
Torsion bar 7 individually sprung dual/track Flat track
Drive sprockets Idlers Shock absorbers
10-tooth front drive Dual adjustable at rear of track On first and last road wheels/track
M109: Track
T136
Center guide, double pin, steel with detachable rubber pad
Width 15"
38cm		 Pitch 6"
15cm		 Shoes/track 79 Ground contact length 156"
396cm
T137
Center guide, single pin, steel with detachable rubber pad
Width 15"
38cm		 Pitch 6"
15cm		 Shoes/track 79 Ground contact length 156"
396cm
M109: Performance
Max level road speed 35mph
56kph		 Max trench 72"
180cm
Max grade 60% Max vertical obstacle 21"
53cm
Min turning diameter Pivot Max fording depth Amphibious with flotation device
Cruising range ~220mi, roads
~350km, roads

The M109 used the same hull and turret as the M108 105mm self-propelled howitzer. The 155mm howitzer had a double-baffle muzzle brake, and a stubby bore evacuator was placed just behind it. M109 was also equipped with a stabilization spade on each corner of the hull rear.

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155mm Self-propelled Howitzer M109A11-8

M109A1: General
Date of first acceptance 1973 Crew
6 men:
  • Chief of section in cab right rear
  • Gunner in cab left front
  • Assistant gunner in cab right front
  • 2 cannoneers in cab
  • Driver in hull left front
M109A1: Dimensions
Combat weight 53,940lbs
kg		 Height over AAMG 129.1"
327.9cm
Length without howitzer 240.7"
611.4cm		 Howitzer overhang forward 115.6"
293.6cm
Width without fenders 124.0"
315.0cm		 Tread 109.0"
276.9cm
Ground clearance 17.7"
45.0cm		 Fire height ~78"
~200cm
Turret ring diameter 100"
250cm		 Ground pressure, zero penetration 11.4psi
.800kg/cm²
M109A1: Armament
Type Mount Ammunition Traverse Max traverse rate Elevation Max elevation rate
155mm Howitzer M185 M127 in turret 28 rounds 360°
(manual and hydraulic)		 11°/sec +75° to -3°
(manual and hydraulic)		 7°/sec
.50cal M2HB MG Flexible in turret AA mount 500 rounds 360°
(manual)		 -- Manual --
Aiming equipment
Panoramic telescope M117 for gunner and telescope M118CA1 for assistant gunner
M109A1: Armor
Assembly
Welding
Hull
Rolled 5083 aluminum alloy
Location Thickness Angle from vertical
Upper front 1.25"
3.18cm		 75°
Lower front 1.25"
3.18cm		 19° and 60°
Sides 1.25"
3.18cm		 0°
Rear 1.25"
3.18cm		 0°
Top 1.25"
3.18cm		 90°
Floor 1.25"
3.18cm		 90°
Turret
Rolled 5083 aluminum alloy
Location Thickness Angle from vertical
Front 1.25"
3.18cm		 22°
Sides 1.25"
3.18cm		 22°
Rear 1.25"
3.18cm		 0°
Top 1.25"
3.18cm		 90°
M109A1: Automotive
Engine General Motors 8V71T; 8 cylinder, 2 cycle, vee, supercharged diesel
Horsepower Net: 345@2,300rpm
Gross: 405@2,300rpm		 Torque Net: 895 ft-lb@1,600rpm
Gross: 980 ft-lb@1,700rpm		 Fuel capacity 135gal
511L
Transmission Allison XTG-411-2A, 4 ranges forward, 2 reverse
Steering Mechanical, steering wheel (clutch-brake in 1st, 2nd, 1st reverse; geared steer in 3rd, 4th, 2nd reverse)
Brakes Multiple disc
M109A1: Suspension
Type Road wheels Track return rollers
Torsion bar 7 individually sprung dual/track Flat track
Drive sprockets Idlers Shock absorbers
10-tooth front drive Dual adjustable at rear of track On first and last road wheels/track
M109A1: Track
T136
Center guide, double pin, steel with detachable rubber pad
Width 15"
38cm		 Pitch 6"
15cm		 Shoes/track 79 Ground contact length 156"
396cm
T137
Center guide, single pin, steel with detachable rubber pad
Width 15"
38cm		 Pitch 6"
15cm		 Shoes/track 79 Ground contact length 156"
396cm
M109A1: Performance
Max level road speed 35mph
56kph		 Max trench 72"
180cm
Max grade 60% Max vertical obstacle 21"
53cm
Min turning diameter Pivot Max fording depth Amphibious with flotation device
Cruising range ~220mi, roads
~350km, roads

The M109A1 used a howitzer with a longer tube than the M126 or M126A1 on the M109, and the bore evacuator had a more slender profile than that on the earlier weapons. The new M185 howitzer allowed use of the M119 propellant charge without affecting the vehicle crew as adversely as the short-tubed howitzer had. The installation of the M185 required minor changes to the turret and a modified travel lock and equilibrator; in addition, the vehicle's hydraulic system and the two forward torsion bars were strengthened. The ammunition rammer was moved from the cab to the ordnance itself. Bowen-McLaughlin-York (later called BMY Combat Systems) started production of 2,741 M109A1s in 1974, and these were designated M109A1B.

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155mm Self-propelled Howitzer M109A21-5,8,11-12

M109A2: General
Date of first acceptance 1976 Total acceptances 1,501
Crew
6 men:
  • Chief of section in cab right rear
  • Gunner in cab left front
  • Assistant gunner in cab right front
  • 2 cannoneers in cab
  • Driver in hull left front
M109A2: Dimensions
Combat weight 55,000lbs
25,000kg		 Height over AAMG 129.1"
327.9cm
Length without howitzer 243.8"
619.3cm		 Howitzer overhang forward 115.6"
293.6cm
Width without fenders 124.0"
315.0cm		 Tread 109.0"
276.9cm
Ground clearance 17.7"
45.0cm		 Fire height ~78"
~200cm
Turret ring diameter 100"
250cm		 Ground pressure, zero penetration 11.8psi
.828kg/cm²
M109A2: Armament
Type Mount Ammunition Traverse Max traverse rate Elevation Max elevation rate
155mm Howitzer M185 M178 in turret 36 rounds 360°
(manual and hydraulic)		 11°/sec +75° to -3°
(manual and hydraulic)		 7°/sec
.50cal M2HB MG Flexible in turret AA mount 500 rounds 360°
(manual)		 -- Manual --
Aiming equipment
Panoramic telescope M117 or M117A2 for gunner and telescope M118A2 or M118A3 for assistant gunner
M109A2: Armor
Assembly
Welding
Hull
Rolled 5083 aluminum alloy
Location Thickness Angle from vertical
Upper front 1.25"
3.18cm		 75°
Lower front 1.25"
3.18cm		 19° and 60°
Sides 1.25"
3.18cm		 0°
Rear 1.25"
3.18cm		 0°
Top 1.25"
3.18cm		 90°
Floor 1.25"
3.18cm		 90°
Turret
Rolled 5083 aluminum alloy
Location Thickness Angle from vertical
Front 1.25"
3.18cm		 22°
Sides 1.25"
3.18cm		 22°
Rear 1.25"
3.18cm		 0°
Top 1.25"
3.18cm		 90°
M109A2: Automotive
Engine General Motors 8V71T Model 7083-7396; 8 cylinder, 2 cycle, vee, supercharged diesel
Horsepower Net: 345@2,300rpm
Gross: 405@2,300rpm		 Torque Net: 895 ft-lb@1,600rpm
Gross: 980 ft-lb@1,700rpm		 Fuel capacity 135gal
511L
Transmission Allison XTG-411-2A, 4 ranges forward, 2 reverse
Steering Mechanical, steering wheel (clutch-brake in 1st, 2nd, 1st reverse; geared steer in 3rd, 4th, 2nd reverse)
Brakes Multiple disc
M109A2: Suspension
Type Road wheels Track return rollers
Torsion bar 7 individually sprung dual/track Flat track
Drive sprockets Idlers Shock absorbers
10-tooth front drive Dual adjustable at rear of track On first and last road wheels/track
M109A2: Track
T136
Center guide, double pin, steel with detachable rubber pad
Width 15"
38cm		 Pitch 6"
15cm		 Shoes/track 79 Ground contact length 156"
396cm
T137
Center guide, single pin, steel with detachable rubber pad
Width 15"
38cm		 Pitch 6"
15cm		 Shoes/track 79 Ground contact length 156"
396cm
M109A2: Performance
Max level road speed 35mph
56kph		 Max trench 72"
180cm
Max grade 60% Max vertical obstacle 21"
53cm
Min turning diameter Pivot Max fording depth 42"
110cm
Cruising range ~220mi, roads
~350km, roads

The M178 mount in the M109A2 incorporated a new rammer, counter-balanced travel lock, and a better recoil system. The M109A2's turret bustle was lengthened to accommodate twenty-two 155mm rounds, and a ballistic cover was mounted to protect the panoramic telescope. Other changes included redesigned door latches, engine warning sensors, and the elimination of the flotation equipment.

M109A1s and M109A1Bs modified to M109A2 standard were designated M109A3 or M109A3B, respectively.

Changes were made during the production run. The double hull rear doors were replaced by a single door. The commander's cupola, originally able to be opened from both inside and out, was redesigned to be only opened from the inside; the traverse mechanism of the cupola was also changed from a ring lock design to one with a latch lock able to hold the cupola in any of 10 positions. An exhaust deflector for the personnel heater was added. A low heat rejection version of the 8V71T engine named the Model 7083-7391 was introduced that developed an additional 35 gross horsepower at 2300rpm.

Starting in 1990, M109A2s and M109A3s were modified to improve reliability, and NBC warfare protection was installed. Vehicles brought up to this standard were called M109A4. The driver and cannoneer number 2 were provided with an air purifier M2A2 and electrical heater M3 in the hull, and another M2A2 and four M3s were in the turret for the rest of the crew. Thirteen subfloor drains were also added to aid in the decontamination process. The traverse mechanism had an hydraulic clutch replace the earlier electric clutch, and an hygroscopic breather and air line filter were added to the hydraulic system. The NATO slave start receptacle was moved to the driver's compartment from the battery compartment. The external telephone terminals were moved from the hull rear bulkhead to the hull rear roof. The earlier 100 ampere generator was replaced by a 180 ampere model.

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155mm Self-propelled Howitzer M109A6 Paladin1-5,12-15

M109A6: General
Date of first acceptance April 1992 Total acceptances 957
Manufacturers
  • BMY Combat Systems
  • United Defense L.P.
Crew 4 men
M109A6: Dimensions
Combat weight 63,600lbs
28,800kg		 Height over AAMG mount 127.4"
323.6cm
Length without howitzer 271.4"
689.4cm		 Howitzer overhang forward in travel position 112.6"
286.0cm
Width over stowage racks 154.4"
392.2cm		 Tread 109.0"
276.9cm
Ground clearance 17.1"
43.4cm		 Fire height ~78"
~200cm
Turret ring diameter 100"
250cm		 Ground pressure, zero penetration 13.6psi
.955kg/cm²
M109A6: Armament
Type Mount Ammunition Traverse Max traverse rate Elevation Max elevation rate
155mm Howitzer M284 M182A1 in turret 39 rounds 360°
(manual and hydraulic)		 11°/sec +75° to -3°
(manual and hydraulic)		 7°/sec
.50cal M2HB MG Flexible in turret AA mount 500 rounds 360°
(manual)		 -- Manual --
Aiming equipment
Panoramic telescope M117A2 for gunner
M109A6: Armor
Assembly
Welding
Hull
Rolled 5083 aluminum alloy
Location Thickness Angle from vertical
Upper front 1.25"
3.18cm		 75°
Lower front 1.25"
3.18cm		 19° and 60°
Sides 1.25"
3.18cm		 0°
Rear 1.25"
3.18cm		 0°
Top 1.25"
3.18cm		 90°
Floor 1.25"
3.18cm		 90°
Turret
Rolled 5083 aluminum alloy
Location Thickness Angle from vertical
Front 1.25"
3.18cm		 22°
Sides 1.25"
3.18cm		 22°
Rear 1.25"
3.18cm		 0°
Top 1.25"
3.18cm		 90°
M109A6: Automotive
Engine General Motors 8V71T; 8 cylinder, 2 cycle, vee, supercharged diesel
Horsepower Net: 345@2,300rpm
Gross: 405@2,300rpm		 Torque Net: 895 ft-lb@1,600rpm
Gross: 980 ft-lb@1,700rpm		 Fuel capacity 133gal
503L
Transmission Allison XTG-411-4, 4 ranges forward, 2 reverse
Steering Mechanical, steering wheel (clutch-brake in 1st, 2nd, 1st reverse; geared steer in 3rd, 4th, 2nd reverse)
Brakes Multiple disc
M109A6: Suspension
Type Road wheels Track return rollers
Torsion bar 7 individually sprung dual/track Flat track
Drive sprockets Idlers Shock absorbers
10-tooth front drive Dual adjustable at rear of track On first and last road wheels/track
M109A6: Track
T136
Center guide, double pin, steel with detachable rubber pad
Width 15"
38cm		 Pitch 6"
15cm		 Shoes/track 79 Ground contact length 156"
396cm
M109A6: Performance
Max level road speed 35mph
56kph		 Max trench 72"
180cm
Max grade 60% Max vertical obstacle 21"
53cm
Min turning diameter Pivot Max fording depth 42"
110cm
Cruising range ~215mi, roads
~346km, roads

The M109A6 came equipped with a new armament suite, higher-strength suspension components, and an NBC protection system with micro-climate cooling. A new turret was produced which had a full-width bustle carrying propellant charges and was protected in places by steel armor. The turret crew was offered additional protection by spall liners. The M109A6 came with a new fire control system with automatic gun laying, ballistic computation, and inertial navigation and positioning capabilities. Rapid-fire bursts were made possible with the assistance of a power-assisted semiautomatic loading mechanism, and the travel lock was also remotely operated. The engine was also upgraded to produce 440 horsepower.

The M284 howitzer was based on the M185, but had a new and stronger torque key to prevent rotation of the howitzer during firing. The earlier ordnance had a single 31/32" (2.46cm) keyway with 10 cap screws and lockwashers, while the new howitzer had two 1-9/16" (3.97cm) keyways with 8 cap screws and lockwashers.

The M109A6 upgrade was expensive, so a cheaper alternative was also designed and dubbed M109A5. Starting in 1995, earlier vehicles were brought up to this standard by fitting them with both the M284 howitzer in the M182 mount and the M109A4's NBC upgrades; the new turret and electronic fire control aids of the M109A6 were omitted. One hundred thirty-seven M108A5s were built.

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References

  1. Hunnicutt, R.P. Sheridan: A History of the American Light Tank, volume 2. Navato, CA: Presidio Press, 1995. Reprinted with permission from Sheridan, R.P. Hunnicutt ©1995, available from Presidio Press, 505B San Martin Drive, Suite 160, Navato, CA 94945.
  2. Zaloga, Steven J. M109 155mm Self-Propelled Howitzer 1960-2005. Botley, Oxford: Osprey Publishing, 2005.
  3. Crismon, Fred W. U.S. Military Tracked Vehicles. Osceola, WI: Motorbooks International, 1992.
  4. Hogg, Ian V. The Greenhill Armoured Fighting Vehicles Data Book. London: Greenhill Books, 2000.
  5. TM 9-2520-234-35 Field and Depot Maintenance Manual for Power Train Assembly (8351100) (Allison Model XTG-411-2A) Composed of: Transfer Assembly, Transmission Input, (2320-894-9535) Transmission Assembly, (2520-894-9533) Drive Assembly, Transmission Output, Vehicle Left, (2520-894-9534) Drive Assembly, Transmission Output, Vehicle Right. Washington, DC: Dept. of the Army, 5 July 1962.
  6. TM 9-2350-217-10N Operation and Maintenance Manual (Crew) for Howitzer, Medium, Self-propelled: 155mm, M109 (2350-00-440-8811) and 155mm, M109A1 (2350-00-485-9662). Washington, DC: Headquarters, Department of the Army, 25 September 1974.
  7. TM 9-2350-217-20 C7 Organizational Maintenance Manual Howitzer, Light, Self-propelled: 105mm, M108 (2350-440-8810) and Howitzer, Medium, Self-propelled: 155mm, M109 (2350-00-440-8811). Washington, DC: Headquarters, Department of the Army, 10 January 1972.
  8. Federation of American Scientists. "M109 155mm SP Howitzer." DOD 101. 27 May 2000. 19 Apr 2001 <http://www.fas.org/man/dod-101/sys/land/m109.htm>. DOD 101
  9. TM 9-2350-217-10 C3 Operator's Manual Howitzer, Light, Self-propelled: 105-mm, M108 (2350-440-8810) and Howitzer, Medium, Self-propelled: 155mm, M109 (2350-00-440-8811). Washington, DC: Headquarters, Department of the Army, 23 November 1964.
  10. TM 9-3305 Principles of Artillery Weapons. Washington, DC: Headquarters, Department of the Army, 4 May 1981.
  11. TM 9-2815-202-34 C1 Direct and General Support Maintenance Manual Engine, Diesel W/Container: Model 7083-7391 (2815-01-335-4579) Engine, Diesel W/Container: Model 7083-7395 (2815-01-043-7092 (2815-01-260-0211) Engine, Diesel W/Container: Model 7083-7396 (2815-01-040-3120) (2815-01-260-0212) Engine, Diesel W/Container: Model 7083-7398 (2815-00-936-7659) Engine, Diesel W/Container: Model 7083-7399 (2815-00-134-4845). Washington, DC: Headquarters, Department of the Army, 9 October 1992.
  12. TM 9-2350-311-10 C6 Operator's Manual for Howitzer, Medium, Self-propelled, 155mm M109A2 (2350--01--031--0586)(EIC:3EZ), M109A3 (2350--01--031--8851)(EIC:3E2), M109A4 (2350--01--277--5770)(EIC:3E8), M109A5 (2350--01--281--1719)(EIC:3E7). Washington, DC: Dept. of the Army, Nov 1994.
  13. TM 9-2350-314-34-2 C4 Direct Support and General Support Maintenance for Cab Systems and Components Howitzer, Medium, Self-propelled: 155mm M109A6 (NSN 2350-01-305-0028) (EIC: 3FC). Washington, DC: Dept. of the Army, 30 Apr 2008.
  14. Federation of American Scientists. "M109A6 Self Propelled Howitzer." DOD 101. 22 Feb 2000. 19 Apr 2001 <http://www.fas.org/man/dod-101/sys/land/m109a6.htm>. DOD 101
  15. Net Resources International. "Army Technology - Paladin 155mm - Self Propelled Howitzer." Army Technology. 20 Apr 2001 <http://www.army-technology.com/projects/paladin/index.html>.
Last updated 15 Jan 2024.
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© Copyright 2001-24 Chris Conners