M109 - 155 mm Self-Propelled Howitzer


In January 1952, a conference was held in Washington DC on the subject of self-propelled artillery which indicated an urgent need for improved self-propelled artillery. Shortly after this conference, preliminary concept studies began for a self-propelled howitzer to replace the 155 mm M44. The first studies for the design of the new vehicle, called the Howitzer 156 mm Self-Propelled T196, were presented to CONARC in August 1952, but were rejected, as were additional studies presented in September 1953. At a conference in May 1954, a concept was finally approved for presentation to CONARC. In June 1954, a conference was held at Fort Monroe to review the military characteristics and to determine the whole self-propelled programme. It was then decided that future concepts of the T196 would be prepared along the design proposed for the Howitzer 110 mm Self-Propelled T195. Concept studies continued along these lines and, in June 1956, it was finally decided to use the basic hull and turret of the T195 but with a 155 mm howitzer instead of the original 156 mm howitzer. In October 1956, the mockup of the T196 was reviewed and verbal authority was given to proceed with development of the first prototype. Main differences from the T195 were power elevating and turret traverse mechanisms, different ammunition racks and two spades at the rear of the hull. The first prototype of the T196 was completed in 1959, about six months later than the 105 mm T195. During preliminary User Evaluation at Fort Knox a number of failures occurred in the suspension. The prototype differed from later vehicles in that it had a different shaped hull and turret, the seventh roadwheel acted as the idler and it was powered by a Continental petrol engine. In 1959 a policy was established that diesel rather than petrol engines would be used for future combat vehicles and the prototype of the T196 was then fitted with a diesel engine and redesignated the T196E1. In February 1961, an order was placed for two T196E1 preproduction vehicles which were delivered within six months. After further trials the T196E1 was classified as a Limited Production Type in December 1961. Two months before this decision, in October, a letter order was given to the Cadillac Motor Car Division for one year's production of the T196E1 at the Cleveland Army Tank Plant. The first production vehicles were completed in October 1962. In January 1963, an extension was authorised to continue the classification of Limited Production and, in July the same year, the T196E1 was classified as standard A and designated the Howitzer, Medium, Self-Propelled: 155 mm, M109. Early in 1963, a contract was awarded to Cadillac for the second year of production. The contract for the third year of production, awarded in December 1963, went to the Chrysler Corporation, although production remained at the Cleveland Army Tank Plant. First M109s were issued to the US Army in June 1963.

Further development of the M109 resulted in the M109A1 and the M109A2 and, by early 1979, production had exceeded 4,000 units.

BMY, now United Defense LP, began production of the M109 in 1974 and in 1994 released the following production figures on the 155 mm M109 series of self-propelled howitzer: M109 HIP (M109A6)

Further development has resulted in the new M109A6 Paladin for which there is a separate entry (qv).

Description (M109) The M109 has a crew of six, consisting of commander, gunner, three ammunition members and the driver. The hull is made of all-welded aluminium armour. The driver is at the front of the hull on the left, the engine is to his right and the turret is at the rear. The driver has a single-piece hatch cover that opens to the left, with three M45 periscopes in front that can be covered by small metal flaps to prevent damage. The Detroit Diesel engine is coupled to an Allison Transmission XTG-411-4A cross-drive transmission which is at the front of the hull. The all-welded aluminium armour turret at the rear of the hull has a square hatch in each side that opens to the rear, and twin doors in the turret rear. The commander is seated on the right side of the turret and has a cupola that can be traversed through 360, a single-piece hatch cover that opens to the rear and an M27 periscope. Pintle mounted on the forward part of the commander's cupola is a 12.7 mm (0.50) M2 HB - also local defence machine gun. The gunner is seated on the left side of the turret and has a square single-piece hatch cover that opens to the right. Twin doors are provided at the rear of the turret for ammunition resupply. Mounted at the rear of the hull, each side of the hull door, is a large spade which is lowered manually to the ground before firing. The torsion bar suspension consists of seven dual rubber-tyred roadwheels with the drive sprocket at the front and the idler at the rear. There are no track-return rollers. The tracks are of the single-pin, centre guide type with replaceable rubber pads. The M109 is fitted with night vision equipment but does not have an NBC system. The basic vehicle can ford to a depth of 1.828 m without preparation. It can be fitted with an amphibious kit consisting of nine air bags, four each side of the hull and one at the front. The bags, which are not carried on the vehicle as part of its normal equipment, are inflated from the vehicle and it can then propel itself across rivers by its tracks at 6.43 km/h. Main armament is an M126 155 mm howitzer in an M127 mount, with a fume extractor and a large muzzle brake. The recoil system is hydropneumatic and the breech block is of the Welin-step thread type. The weapon has an elevation of +75, a depression of -5 and the turret can be traversed through a full 360. Gun elevation and depression and turret traverse are hydraulic with manual controls for emergency use. Normal rate of fire is 1 rd/min but 3 rds/min can be fired for a short period. Fire-control equipment includes an elbow telescope M118C for direct fire with a magnification of x4 and a 10 field of view, panoramic telescope M117 for indirect fire with a magnification of x4 and a 10 field of view, quadrant fire control M15 and gunner's quadrant M1A1. The weapon can fire the following types of ammunition:
Copperhead Cannon-Launched Guided Projectile M712 with a range of 16,400 m
HE (M107) with the projectile weighing 42.91 kg, a maximum muzzle velocity of 562.4 m/s and a maximum range (charge 7) of 14,600 m
HE (M795) which is the replacement for the M107; the projectile weighs 46.90 kg
HE (M449A1) (carries 60 anti-personnel grenades) with the projectile weighing 43.09 kg, a maximum muzzle velocity of 563 m/s and a maximum range of 14,600 m
HE (M483A1 series) (carries 64 M42 and 24 M46 dual-purpose grenades) with the projectile weighing 46.53 kg, a maximum muzzle velocity of 535.2 m/s and a maximum range (charge 7) of 14,320 m
HE (M692) (carries 36 anti-tank mines) with the projectile weighing 46.49 kg, a maximum muzzle velocity of 535.2 m/s and a maximum range (charge 7) of 14,320 m
M718/M741 (containing nine anti-tank mines) with a maximum range of 14,320 m
HE (M731) (carries 36 anti-personnel mines) with the projectile weighing 46.49 kg, maximum muzzle velocity of 535.2 m/s and a maximum range (charge 7) of 14,320 m
HERA (M549) with the projectile weighing 43.54 kg, with a maximum range (charge 7) of 19,300 m
Illuminating (M485) with the projectile weighing 41.73 kg, a maximum muzzle velocity of 576.9 m/s and a maximum range (charge 7) of 13,586 m Illuminating (M818) with the projectile weighing 46.26 kg, a maximum muzzle velocity of 536 m/s and a maximum range of 11,600 m Smoke (M825) with the projectile weighing 46.53 kg, a muzzle velocity of 535.2 m/s and a maximum range of 14,320 m Smoke BE (M116 series) with the projectile weighing 42.22 kg, a maximum muzzle velocity of 562.4 m/s and a maximum range (charge 7) of 14,600 m
Smoke WP (M110 series) with the projectile weighing 44.4 kg, a maximum muzzle velocity of 563.9 m/s and a maximum range (charge 7) of 14,600 m M804 Practice.



The M109A2 entered production at BMY Combat Systems in 1978, with first deliveries made early in 1979. The first production quantity of 103 vehicles was with FY77 funding. Major changes from the M109A1 include a redesigned rammer and improved recoil mechanism, engine operation warning devices, a redesigned hatch and door latches, an improved hydraulic system and a bustle designed to carry an additional 22 rounds of ammunition.
M109A2 pro 36 M109A2s were produced for the National Guard using FY82 funds. There has been no recent procurement of the M109A2/M109A3 by the US Army or Marine Corps.

M992 Field Artillery Ammunition Support Vehicle

Originally developed as a private venture by Bowen-McLaughlin-York, the XM992 was type-classified M992 in 1983. The M992 Field Artillery Ammunition Support Vehicle (FAASV) is basically the chassis of a standard M109 155 mm self-propelled howitzer with the turret replaced by a fully enclosed superstructure. Inside this superstructure, which has the same protection as the rest of the vehicle, can be stacked 93 155 mm projectiles, 99 propellant charges and 104 fuzes. The ammunition can be loaded into the superstructure by a front-mounted crane and is fed from the vehicle along a conveyor to the recipient self-propelled howitzer; this crane was not fitted to US Army M992 vehicles but is offered for export. All ammunition handling within the M992 is mechanical. In use, the M992 backs up to the user M109 and the conveyor delivers the 155 mm ammunition at the rate of up to 8 rds/min to the M109 bustle or lower hatches. The M992 can have a crew of two plus six passengers and the weight fully loaded is 25,900 kg. Intended primarily for use with M109 field units, the M992 can also be used by units with 175 mm, 203 mm, 120 mm and 105 mm self-propelled weapons. With 203 mm units the M992 can carry 48 203 mm projectiles, 53 charges and 56 fuzes. It has been suggested that the M992 could form the basis for a family of battlefield vehicles including a Fire Direction Centre Vehicle (see below), Command Post Vehicle (CPV), Medical Evacuation Vehicle (MEV), Maintenance Assistance Vehicle (MAV) and Armoured Forward Area Rearm Vehicle (AFARV). US Army testing and decisions relating to the M109A6 Paladin reaffirmed the need for an FAASV in direct, organic support of each self-propelled gun. The US Army has improved the basic M992 through a series of upgrades to M992A1 and M992A2 configurations. The US Army recently type-classified the M992A1. The M992A1 contains a series of improvements based on lessons learned during the extensive operational testing of the M109A6 Paladin self-propelled howitzer.

Fire Direction Centre Vehicle

The Fire Direction Centre Vehicle (FDCV), based on the chassis and hull of the M992 FAASV, has been tested at the US Army School of Artillery at Fort Sill to prove the feasibility and function of the concept under field and NBC conditions. The equipment used in the FDCV is a mix of 'off-the-shelf' or prototype products assembled for the concept, for which the internal headroom and armour of the M992 hull is eminently suitable. If required, bolt-on armour can be added to protect the specialist personnel and equipment carried. The following equipment was carried in the prototype FDCV: mast system with OE254 antenna which is 11.28 m high when elevated; mast elevation control box; mast elevation control power unit; packet digital radio; RT524/VRC receiver/transmitter radios (4); printer; liquid cooling vest connect points (9 stations); tactical graphics terminal; tactical display; ANS 2000 land navigation system display; ANS 2000 land navigation system heading reference unit; M13A1 filtered air system for NBC ventilated facepieces; M43 NBC detector; M42 alarm; M49 NBC collective protective system; APU; air-conditioner (36,000 BTU cooling/heating); ventilation filter/blower; HEL computer (PDP1134); plotter; CRT terminal; digitiser; liquid cooling vest control box; M10 protective entrance; battery boxes and batteries; liquid cooling vest chilling unit; four extra personnel seats and additional stowage compartments.

Other M109 Chassis Applications

The chassis of the M109, or versions of the M109, have been used for a wide range of other applications. These include the XM-11S threat radar simulator from General Dynamics. This was developed for the US Army Missile and Space Intelligence Centre and is used to simulate the Russian SA-11 ('Gadfly') surface-to-air missile system. The XM975 Roland chassis, based on the M109, was used as the basis for the Robotic Command Center for use in various robotic vehicle programmes.


Crew: 6
Combat weight: 24,948 kg
Unloaded weight: 21,110 kg
(gun forward) 9.12 m
(hull) 6.19 m
Width: 3.15 m
(incl anti-aircraft MG) 3.28 m
(reduced) 2.8 m
Ground clearance: 0.46 m
Track: 2.788 m
Track width: 381 mm
Length of track on ground: 3.962 m
Max road speed: 56.3 km/h
Fuel capacity: 511 litres
Max road range: 349 km
Fording: 1.07 m
Gradient: 60%
Side slope: 40%
Vertical obstacle: 0.53 m
Trench: 1.83 m
Engine: Detroit Diesel Model 8V-71T, turbocharged, 2-stroke, liquid-cooled 8-cylinder diesel developing 405 bhp at 2,300 rpm Transmission: Allison Transmission XTG-411-4A cross-drive with 4 forward and 2 reverse gears
Suspension: independent torsion bar
Electrical system: 24 V
Batteries: 4 x 12 V Model 6TN
(main) 1 x 155 mm M185 howitzer
(anti-aircraft) 1 x 12.7 mm or 7.62 mm MG
Smoke-laying equipment: none
(main) 34 plus 2 CLGP
(12.7 mm anti-aircraft) 500
Gun control equipment
Turret power control: hydraulic/manual
(by commander) no
(by gunner) yes
Gun elevation/depression: +75/-3
Turret traverse: 360
NBC system: no
Night vision equipment: yes


The M109 and its derivatives are in service with the US Army, Marine Corps and National Guard. Other nations using M109 series weapons are listed left. During the first production phase, carried out initially by the Cleveland Army Tank Plant, US-configured M109s were delivered to the following nations: Austria, Belgium, Canada, Denmark, Ethiopia, Iran, Israel, Jordan, Netherlands, Spain, Switzerland and the UK. Italy, the Netherlands and Norway formed co-production agreements. Canada, Iran, Israel, the Netherlands, Spain, Switzerland and the UK have converted their M109s to the M109A1 configuration. M109Gs were delivered to Germany, Italy and Norway. M109A1B FMS production since 1972 has resulted in systems for Greece, Iran, Israel, Italy, Jordan, Kuwait, Morocco, Netherlands, Pakistan, Portugal, Spain, Taiwan and the UK. M109A2 production since 1980 has resulted in deliveries to Austria, Jordan, Kuwait, Netherlands, Pakistan, Portugal, Spain, Taiwan and the UK. Known sales of the M109 series of self-propelled howitzers are in the table.

Country M109A2 Pakistan 152

Note: Libya has also acquired a number of M109s. Netherlands is to reduce its M109 fleet to 137 systems and in mid-1995 sold 85 systems to the UAE. Additional details are given under RDM Technology Upgrades in the Netherlands.

COMPANY NAME : United Defense LP, Ground Systems Division