155-mm M109 Paladin


---- 105-mm M108 SP howitzer (variation based on early prototype)
---- K55 (South Korean designation)
---- M109A5E Espana (Spanish designation)
---- M109A6 Paladin (U.S. upgrade)
---- M109AL Rochev (Israeli designation)
---- PzHb 66/74 (Swiss designation)
---- PzHb 74/88 (Swiss designation)
---- PzHb 88/95 Bison (Swiss designation)
---- Rechenstelle (Austrian fire direction center version)
---- SP122 (Egyptian D-30 armed casemate version)
---- VBCL (Belgian command version)
---- XT-69 (Taiwanese open gun mount version)

EQUIPMENT CATEGORY: Artillery/Guns -- Self-Propelled Guns/Howitzers

PICTURES OF: 155-mm M109 Paladin


The widely used M109 carries a 155-mm howitzer and is the principal self-propelled artillery support for U.S. Army divisions. It is a large tracked vehicle with a fully traversable turret and prominent bustle. Early variants had a short, 23-caliber barrel. Later versions, including the M109A6 Paladin, have a 39-caliber barrel.

The M109 has a crew of six: commander, gunner, driver and three ammunition members. The hull is made of all-welded aluminum armor, which protects against small-arms fire and shell splinters.

The driver is seated at the front left of the hull, with the powerpack to the right and the turret at the rear. The driver is provided with a single-piece hatch cover that opens to the left, with three M45 day periscopes in front. These can be covered with small metal flaps to prevent damage. One of the day periscopes can be replaced by a passive night-vision periscope.

The Detroit Diesel Model 8V-71T engine is coupled to an Allison Transmission XTG-411-4A cross-drive transmission.

The all-welded aluminum armor 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 deg, a single-piece hatch cover that opens to the rear and an M27 day periscope. A .50-cal M2 heavy-barrel machine gun is pintle-mounted on the front of the cupola.

The gunner is seated on the left side of the turret and has a square single-piece hatch cover that opens to the right. The twin doors at the rear of the turret are provided for ammunition resupply. Mounted at the rear of the hull on each side of the hull door is a large spade that is manually lowered to the ground before firing. They are normally deployed only when firing top charges.

The torsion bar suspension on either side consists of seven dual rubber-tired road wheels with the drive sprocket at the front and the idler at the rear. There are no track-return rollers. The tracks are of a single-pin, center-guide type with replaceable rubber pads.

The M109 is fitted with night-vision equipment, but does not have nuclear, biological and chemical (NBC) warfare protection. The vehicle can be fitted with an amphibious kit consisting of nine air bags, four on each side of the hull and one at the front. The bags are inflated from the vehicle, which can then propel itself across rivers on its tracks at a maximum speed of 4 mph (6 kmh).

The main armament is a 155-mm M126 howitzer in an M127 mount with a fume extractor and large muzzle brake. The recoil system is hydropneumatic and the breech block is of the Welin-step thread type. Gun elevation and depression and turret traverse are hydraulic with manual controls for emergency use.

Fire-control equipment includes an elbow telescope M118C for direct fire with a magnification of 4x and 10-deg field of view; panoramic telescope M117 for indirect fire and gunner's quadrant M1A1 .

Under a contract awarded in October 1985, BMY (then United Defense Limited Partnership-UDLP and now BAE Systems), York, Pa., began a howitzer improvement program (HIP) in which A2 hulls were refurbished and mated with a new turret. The Paladin upgrade was a major product improvement program (PIP) that provided numerous enhancements, including reliability, availability, maintainability, survivability, lethality and responsiveness to older-model M109 howitzers.

The first armament modification phase substitutes the M284 gun for the A2/A3s M185. Modifications include a strengthened gun mount to prevent barrel rotation with maximum charge. Later armament options include the XM283, derived from M198 towed 155-mm howitzer. It has the same interior ballistics as the M284, but is more reliable. XM282 is a 58-caliber cannon designed to fire M864 base-bleed projectile to 28 mi (45 km).

The Paladin consists of 1,900 parts. Major components include a low-heat rejection engine from Detroit Diesel; Honeywell navigation/positioning system; and an Alliant Techsystems automatic fire-control system (AFCS).

The AFCS has a ballistic computer/weapon controller, power conditioner and an inertial reference navigation systems/dynamic reference unit based on the modular azimuth positioning system (MAPS) using ring laser gyro on-board land navigation. The AFCS permits 0.6 mi. (1 km) separation between vehicles, improving gun battery survivability.

The AFCS was plagued by software problems and random computer lockups that were solved only by shutting down the entire system and rebooting. The software glitches involved interference between the fire-control and navigation modules.

DuPont Kevlar armor has been added to the Paladin, forming an inner lining of the cab, roof and crew compartment sides. Rolled homogeneous steel armor is fitted over the driver's compartment and on the rear of the bustle. An upgraded suspension has longer torsion bars and hydropneumatic bumpstops to handle the greater vehicle weight. Both engine cooling and the electrical system have been improved, the latter including a sealed starter.

Mean time between failure (MTBF), which averages 75 hours in the A3, is increased to 122 hours, according to BMY. Mean time to repair (MTTR), estimated at 4.5 hours in the A3, was reduced to 2 hours for later versions of the Paladin.

Improved protection also includes the segmentation of hydraulic lines and the use of a Halon fire-suppression system. The hydraulic system, which is distributed in the A3, has been centralized in the Paladin. The Halon system is intended to snuff out internal fires in less than 0.25 sec. In addition, a microclimate cooling system has been added to improve the working environment and protect against the effects of nuclear, biological and chemical (NBC) warfare. Projectile stowage has been placed lower in the hull to reduce threat of secondary explosions from counter-battery fires.

According to United Defense, the Paladin can move from road march to firing status in one minute. Response time while in firing position is less than 30 seconds. These reaction times give Paladin a true "shoot-and-scoot" capability. The Paladin's travel lock, a front-mounted bracket that steadies the long barrel during vehicle movement, has been modified to enable remote operation.

The gun fires high-explosive (HE) rounds with 14.6 lb (6.62 kg) of trinitrotoluene (TNT) or 15.4 lb (6.98 kg) of Composition B explosive; M692/M731 HE area denial artillery munition (ADAM); M718/M741 anti-tank remote anti-armor mine system (AT-RAAMS); rocket-assisted HE (HERA) with 16 lb/7.25 kg Comp B (M549) or 15 lb/6.8 kg TNT (M549A1); Copperhead cannon-launched guided projectiles (CLGP); nuclear; XM867 artillery delivered expendable communications jammer (ADEXJAM) submunitions; chemical; smoke; and illumination rounds.

The M483 round carries eight layers of M42 dual-purpose grenades ahead of three layers of M46 grenades, the difference being a stronger case on the M46 to absorb the "setback load" when the gun is fired. The ADAM rounds dispense 36 anti-personnel mines; the designators distinguish between long self-destruct and short self-destruct fuzes. The RAAMS rounds plant nine magnetic anti-tank mines. The M864 base-burn dual-purpose improved conventional munitions (DPICM) projectile is a successor to the M483; it projects 24 M46 and 48 M42 grenades 30 percent farther than the M483.



In service.

Initial operational capability (IOC) for the M109 was in 1963; M109A1 in 1973; M109A2 in 1979; and M109A6 in 1992. The T196 prototype was ordered in October 1956. There were 2,111 M109s built by Cadillac Motor Car (FY1962-1963), Chrysler Corp. (FY1964) and Allison Division of General Motors (FY1965-1969) at the Cleveland Army Tank Plant. The M109A1 and later were built by BMY Combat Systems (formerly Bowen-McLaughlin-York, now United Defense) of York, Pa.

Samsung Shipbuilding and Heavy Industries (SHI) assembles M109A2 howitzers under a series of agreements with BMY (United Defense), the first of which was signed in 1984. BMY manufactured most of the main components and delivered kits to SHI, which adds locally produced components. Approximately 1,000 howitzers were delivered to the South Korean army through 1995.

Low-rate production of the M109A6 HIP (howitzer improvement program) Paladin was approved in February 1990. A $74 million contract for 44 Paladins was awarded to BMY (United Defense) in September 1990 with work completed by Jan. 31, 1993. A later option for 60 more, which was exercised in April 1991 in a $29.6 million contract, called for delivery by Jan. 31, 1994. Some thought was given to undertaking later production at a U.S. Army depot (see "Issues").

Iraq's holdings of M109s were entirely made up of war prizes. In addition to an unknown number of Iranian M109s taken during the 1980-1988 Gulf War, Iraq was believed to have captured 18 Kuwaiti M109s in its August 1990 invasion and annexation of Kuwait.

Britain has replaced all M109s in its service with the AS90 self-propelled howitzer (see separate record for details).

Egypt requested the possible purchase of 279 M109A2/A3s on May 24, 2000. Cairo intends to use them to replace Soviet-era towed artillery. The total cost of the vehicles, training, equipment and spares was reported at $48 million.

A possible sale to Greece seems to have been derailed by Athens' decision to purchase German-made PzH 2000s in 2002.

In 2004, it was reported that Chile was slated to take delivery of 24 ex-Swiss M109s beginning in 2005.

In July 2005, the U.S. Defense Security Cooperation Agency (DSCA) reported that Egypt had requested to buy 200 surplus U.S. Army M109A5 SP howitzers (SPH) in a contract valued at US$181 million. The deal also includes related logistics and training packages.

Defense News for April 18, 2005, reported that the Canadian army was replacing its M109 SP howitzers. Training on the M109 had stopped by that time and it was withdrawn from service during the summer of 2005.

BAE Systems announced on Oct. 9, 2007, that it had signed a memorandum of understanding with the U.S. Army to establish a public-private partnership to develop and sustain the service's M109 vehicles. The partnership is intended to ensure the cost-effective and on-time reset of the current fleet of M109A6 Paladin self-propelled howitzers and M992A2 field artillery ammunition supply vehicles (FAASV), as well as the planned production of the M109A6/M992A2 Paladin Integrated Management (PIM) vehicles. BAE Systems unveiled the PIM program earlier that month at the Association of the U.S. Army exhibition in Washington, D.C.

BAE Systems received a $21.8 million Army contract modification on May 15, 2008, for the design and development of M109A6 Paladin Integrated Management (PIM) vehicles. The award represented the first stage of the long-term PIM program to sustain the M109 fleet through 2050, according to a company release. The contract brought the program value to $26.8 million. Under the deal, BAE was to conduct design and engineering analysis work for the vehicle structure, automotive systems and electric and vehicle electronics ahead of a planned remanufacture program for the Paladin fleet.

On Nov. 4, 2008, BAE Systems announced it had been awarded a $20 million contract to produce and deliver 140 Paladin digital fire-control systems (PDFCS) kits and more than 60 spare components for Army M109A6 Paladins. The deal was part of a larger contract that covered a total of 450 kits. Deliveries were scheduled to be completed by January 2010.

On June 12, 2009, the U.S. Defense Security Cooperation Agency announced a potential $275 million sale of military equipment to Chile. The possible sale included 12 M109A5 and 12 M109A3 howitzers.

In August 2009, BAE Systems received a $63.9 million Army contract for the production of seven M109 PIM vehicles: five howitzers and two field artillery ammunition support vehicles (FAASVs). The initial PIM vehicles are slated for contractor testing in Yuma, Ariz., and Aberdeen, Md., before beginning government testing in January 2011.

BAE Systems unveiled the M109A6 PIM on Jan. 20, 2010, at its York, Pa., facility. The rollout involved the first of seven vehicles ordered in August 2009.

The U.S. officially delivered 48 M109A5 howitzers to the Pakistani army on Feb. 13, 2010, at the Malir Cantonment in Karachi. The delivery completed a 2006 order for 115 Paladins under the U.S. Foreign Military Sales program.

In May 2010, Army officials said they planned to buy 440 M109A6 PIM vehicles to meet immediate requirements. The Fires Center of Excellence and the Army's Training and Doctrine Command is expected to conduct an analysis of alternatives to consider a long-term solution for the Army's self-propelled howitzer requirements. The Army requested funding for 18 PIMs for fiscal 2011, but a new program schedule delayed a low-rate initial production decision until June 2013.

On Oct. 4, 2011, BAE Systems announced that it had received a $15.8 million contract to refurbish and upgrade 12 M109A5 howitzers for the Chilean army under the U.S. Foreign Military Sales program. Under the contract, the U.S. is providing the howitzers to Chile, while BAE performs the refurbishment and upgrade work. Refurbishment will include replacing obsolete equipment and returning the vehicles to a "like new" condition. Digital data connectivity and gun positioning and navigation systems will also be installed. Work under the contract is scheduled to conclude in October 2012.

BAE Systems received a $313 million Army contract on Jan. 18, 2012, for additional engineering design, logistics development and test evaluation support to complete the engineering and manufacturing development phase of the Paladin Integrated Management (PIM) program. Work under the contract is scheduled to be completed in January 2015.


 Prime Contractor:
 United Defense, Ground Systems Division, York, Pa. (now BAE Systems Ground Systems)

 Licensed Production:
 Samsung Shipbuilding and Heavy Industries, South Korea


 Austria                   [152] (M109A2/A3/A5OE)
 Bahrain                   [20] (M109A5)
 Brazil                    [37] (M109A3)
 Chile                     [36] (24 M109A3, 12 M109A5)
 Denmark                   [24] (M109)
 Egypt                     [368] (164 M109A2, 204 M109A5)
 Germany                   [288] (M109A3G)
 Greece                    [195] (M109A1/A2/A3GEA1/A5)
 Iran                      [180] {M109}
 Iraq                      [2] (M109A1/A2)
 Israel                    [350] (M109A1/A2)
 Italy                     [124] (M109L)
 Jordan                    [253] (M109A1/A2)
 Kuwait                    [23] (M109A3)
 Libya                     [14] (M109)
 Morocco                   [127] (84 M109A1/A1B, 43 M109A2)
 Norway                    [54] (M109A3GN)
 Pakistan                  [430] (200 M109A2, 230 M109A5)
 Peru                      [12] (M109A2)
 Portugal                  [20] (6 M109A2, 14 M109A5)
 Saudi Arabia              [110] (M109A1B/A2)
 South Korea               [1,040] (M109A2 [K55/K55A1])
 Spain                     [96] (M109A1/A5)
 Switzerland               [200] (PzHb-66/74/79/88 (M109U))
 Taiwan                    [225] (M109A2/A5)
 Thailand                  [20] (M109A2)
 United Arab Emirates      [125] (M109A3)
 USA                       [1,594] (M109A1/A2/A6)


   M109A2/A3               6 (commander, gunner, 3 loaders, driver)
   M109A5                  5 (chief of section, gunner, assistant gunner,
                              No. 1 cannoneer and driver)
   M109A6                  4

      combat               55,000 lb (24,948 kg)
      ground pressure      11.83 lb/sq in (0.83 kg/cm sq)
      combat               55,000 lb (24,948 kg)
   M109A6 Paladin
      combat               63,600 lb (28,848 kg)
      ground pressure      13.53 lb/sq in (0.95 kg/cm sq)
   M109A6 PIM
      gross                70,000 lb (31,751 kg)

   All Models
         hull              20 ft  4 in (6.19 m)
         over skirts       10 ft  4 in (3.15 m)
         length on ground
                           12 ft  1 in (3.69 m)
         width              1 ft  3 in (0.38 m)
   Ground clearance         1 ft  6 in (0.46 m)
         gun forward       29 ft 11 in (9.12 m)
         w/ADMG            10 ft  9 in (3.28 m)
   M109A6 Paladin
         w/rear box        22 ft  4 in (6.81 m)
         gun forward       31 ft  9 in (9.68 m)
         w/ADMG            10 ft  7 in (3.24 m)
         over side boxes   12 ft 10 in (3.92 m)
         overall           11 ft 11 in (3.62 m)
         top of MG mount   10 ft  9 in (3.27 m)
      track                 9 ft  1 in (2.78 m)
         length on ground
                           13 ft  0 in (3.96 m)
   M109A6 PIM
      length               31 ft 10 in (9.71 m)
      width                12 ft 11 in (3.93 m)
      height                9 ft 10 in (3.00 m)
      ground clearance      1 ft  7 in (0.48 m)
         combat loaded      1 ft  7 in (0.47 m)

      engine               General Motors 8V-71T 569-cu in (9.32-liter)
                              liquid-cooled, turbo-charged 2-stroke V-8
      power                405 hp at 2,300 rpm
      power-to-weight ratio
                           16.23 hp/ton
      fuel                 135 gal (511 liters)
      transmission         Allison ATD-XTG 411-2A (A3) or 411-4 with quick
                              disconnect powershift crossdrive, 4 forward and
                              2 reverse gears
      engine               General Motors 8V-71T LHR, 9310cc, 2-cycle
      power                440 hp
      power-to-weight ratio
                           17.96 hp/ton
      fuel                 135 gal (511 liters)
      transmission         Allison ATD-XTG 411-4A, 4 forward and 2 reverse
   M109A6 Paladin
      engine               DDC 8V-71T 568-cu in (9.3-liter) liquid-cooled,
                              turbo-charged two-stroke V-8 diesel/JP8
      power                440 bhp
      power-to-weight ratio
                           15.25 hp/metric ton
      fuel                 133 gal (503 liters)
      transmission         Allison ATD-XTG 411-2A (A3) or 411-4 with quick
                              disconnect powershift crossdrive, 4 forward and
                              2 reverse gears
   Suspension              torsion bar, 7 road wheels, front drive, rear
                              idler, no return rollers (all models except
   M109A6 PIM
      engine               Cummins diesel
      power                600 hp
      fuel                 140 gal (530 liters)
      transmission         L-3 HMPT-500
      suspension           Bradley road arm assemblies, torsion bars and
                              idler assemblies, six road wheels
         Amperes           180
         Volts             24
      M109A6 Paladin
         Amperes           650
         Volts             24

   All Models
         vertical          1 ft  9 in (0.53 m)
         trench            6 ft  0 in (1.83 m)
      fording              amphibious with airbags
         w/out preparation
                           3 ft  3 in (1.00 m)
      gradient             60 percent
      side slope           40 percent
      speed                35 mph (56 kmh)
      range                220 mi (354 km)
   M109A6 Paladin
      speed                40 mph (64 kmh)
      range                214 mi (344 km)
   M109A6 PIM
      speed                38 mph (61 kmh)
      range                186 mi (300 km)
      fording              3 ft  6 in (1.07 m)

   All Models
         grooves           48
         rifling           right-hand rifling with constant, 8.93-deg twist
         breech type       Welin-step thread
         recoil system     hydropneumatic
         elevation         -3/+75 deg (-53/+1,333 mils)
         traverse          360 deg (6,400 mils)
      air defense          1 x 12.7-mm MG mounted on commander's cupola
         ammunition        500 rounds
      cannon               155-mm/39-cal M185 rifled howitzer fitted w/muzzle
                              brake and fume extractor
         ammunition        12 conventional, 2 Copperhead rounds
      range by round type
         M864              24,175 yd (22,000 m) max
         M483A1            15,951 yd (14,586 m) full charge
                           19,400 yd (17,740 m) maximum
         M718/M741         15,951 yd (14,586 m) full charge
                           19,400 yd (17,740 m) maximum
         M692/M731         15,951 yd (14,586 m) full charge
                           19,400 yd (17,740 m) maximum
      response time        11 min
      rate of fire         1 rd/min first hour;
                           4 rd in first 3 min max
      machine gun          1 x M2 .50 caliber
         ammunition        500 rounds
      cannon               155-mm/39-cal M284 rifled howitzer fitted w/muzzle
                              brake and fume extractor
         ammunition        34 complete rounds
      range by round type
         as M109A2/A3
         assisted          32,967 yd (30,000 m) maximum
         unassisted        24,175 yd (22,000 m) maximum
      rate of fire         1 rd/min first hour;
                           4 rd in first 3 min max
   M109A6 Paladin
      cannon               155-mm/39-cal M284 rifled howitzer fitted w/muzzle
                              brake and fume extractor
         ammunition        39 rounds including 2 Copperhead
      range by round type
         M549A1 HERA       32,976 yd (30,000 m)
         HE                26,247 yd (24,000 m)
         M864 DPICM        24,175 yd (22,100 m)
         assisted          32,967 yd (30,000 m) maximum
         unassisted        24,175 yd (22,000 m) maximum
      response time        60 sec
      rate of fire         1 rd/3 min sustained;
                           3 rd/15 sec max; 8 rd/min if using optional
                              semi-automatic loading system and automatic
                              primary feeder

 Type                  Weight                 Length
 M712 Copperhead       140.0 lb (63.50 kg)    54.0 in (1,372 mm)
 M864 DPICM            103.2 lb (43.80 kg)    35.3 in (  898 mm)
 M825 Smoke WP         103.0 lb (46.72 kg)    unknown
 M718 RAAMS Long       103.0 lb (46.71 kg)    30.7 in (  781 mm)
 M741 RAAMS Short      103.0 lb (46.71 kg)    30.7 in (  781 mm)
 M692 ADAM Long        102.5 lb (46.49 kg)    31.6 in (  803 mm)
 M731 ADAM Short       102.5 lb (46.49 kg)    31.6 in (  803 mm)
 M483A1 HE             102.5 lb (46.49 kg)    35.4 in (  899 mm)
 M121 Chem GB/VX        98.9 lb (44.86 kg)    26.9 in (  684 mm)
 M110 Smoke WP          97.9 lb (44.40 kg)    23.7 in (  602 mm)
 M631 Chem CS           96.7 lb (43.88 kg)    23.8 in (  604 mm)
 M549 HERA              95.9 lb (43.54 kg)    33.7 in (  858 mm)
 M449 APICM             95.0 lb (43.09 kg)    27.5 in (  698 mm)
 M107 HE                94.6 lb (42.91 kg)    23.9 in (  607 mm)
 M110 Chem HD           94.6 lb (42.91 kg)    23.9 in (  607 mm)
 M485A2 Illum           93.6 lb (42.48 kg)    23.7 in (  602 mm)
 M116 Smoke HC          93.0 lb (42.22 kg)    23.4 in (  594 mm)
 M867E1 Chem Binary     unknown               unknown

   All Models
      infrared             night-vision devices
   M109A5 SPH
      optics               Optical-Survey

      armor                light alloy aluminum to protect against small-arms
                              fire and shell splinters
      NBC                  none fitted
      armor                maximum 20-mm light alloy aluminum, small-arms and
                              artillery fragment protection
      NBC                  ventilated face piece system (VFPS)
      fire suppression     CO2 fire extinguisher system in crew and engine
   M109A6 Paladin
      armor                5083 aluminum with composite spall liners and
                              supplemental armor
      NBC                  MCS system
      fire suppression     automatic


105-mm M108 SP howitzer

This version had the T196 development designation. It was designed at the same time as the M109. The weapon mounts a 105-mm M103 howitzer with small fume extractor but no muzzle brake. It was produced only in 1962-63. It is in service in Brazil, Spain, Taiwan and Turkey.

105-mm M109 SP howitzer

This is the original production model developed from T-196 and T-196E1. Combat weight is 52,438 lb (23,786 kg); hull length with the gun forward is 21 ft 8 in (6.61 m). Maximum vehicle range of 242 mi (390 km). It has a short (23-caliber) 105-mm M126 howitzer with muzzle brake and a distinctive large "lazy D"-shaped fume extractor. Maximum M126 range of 15,914 yd (14,600 m). The vehicle carried 28 rounds.

M109A1 (1970)

This version mounts the longer M185 155-mm gun and incorporated elevation, traversing and suspension improvements. It can fire a high-explosive round 19,800 yd (18,100 m). The M109A1 weighs 53,070 lb (24,070 kg) fully loaded and is 29-ft 8-in (9.04-m) long including the barrel.

The first M109A1 conversion kits became available in early 1972 and the first examples, converted from standard models, became operational in 1973.

M109A2 (1978)

This howitzer features many detail improvements, including a redesigned rammer and improved recoil mechanism, engine operation warning devices, redesigned hatch and door latches, improved hydraulic system and larger turret bustle carrying 36 155-mm projectiles. Production began in 1978 with initial deliveries the following year. About 836 were produced for the U.S. Army and Army National Guard.

M109A3 (1980)

This variant has an improved M178 mounting, boresight alignment driver and selected RAM and safety kits, which included a fuel system air purge; driver's instrument panel; bustle/rack; propellant stowage; torsion bar; counter-recoil buffer; and upper recoil cylinder. The designation also applies to retrofitted models.


These are 737 U.S. Army Reserve component howitzers refitted under the NBC and reliability, availability and maintainability (RAM ) program; they were completed in FY1992. Includes:
  • 180-amp electrical charging system;
  • vaneaxial fan assembly increases cooling capacity and reliability;
  • two hydraulic filters replacing one power-pack filter;
  • external power receptacle;
  • crew compartment sub-floor drains for torsion-bar pockets;
  • traverse mechanism upgrade of internal gearing and clutch and addition of hydraulic tubing and external clutch valve;
  • rewire air cleaner switch to shut off when vehicle's in neutral;
  • add starter-circuit relay to prevent over-ranking;
  • move slave-start receptacle to driver's compartment; and
  • added protective covers over sensors mounted on engine hood.

M109A5 (1993)

This was a further upgrade of M109A4 with the reserve component/modified armament system (RC/MAS) that, with the installation of the M284 cannon assembly and M182 gun mount, brings the weapon to A6 standard. Upgrades were completed in FY1993.

The M109A5 offers upgraded components providing greater durability. It has a higher horsepower low heat rejection (LHR) engine and an improved transmission for increased performance. There is also a protection device to prevent starter burnout and a 180-amp alternator that extends battery life. The elevation/equilibrium cylinder and turret traverse clutch assembly are redesigned to prevent failures. Protective covers for the engine electrical sensors are provided to prevent accidental damage. Relocated and easily accessible filters improve hydraulic power pack filtration and easy to replace track pads and external road wheel lubrication points simplify maintenance. The suspension system has been strengthened and an external NATO power receptacle allows the M109A5 to be electrically powered by the M992 field artillery ammunition support vehicle (FAASV).

The M109A5 share commonality with all of the other M109 family members and fires all NATO-standard 155-mm ammunition.

Customers for the M109A5 include Greece (12 delivered from 1998), Taiwan (28 delivered in 1998) and Thailand (20 delivered).

M109A6 Paladin

This is a merger of the M109 howitzer improvement program (HIP) and howitzer extended life program (HELP). It included creating a new gun mount that accepts 39- and 58-caliber 155-mm cannon in development at the Watervliet Arsenal, Watervliet, N.Y.

The program was approved in November 1984. Live-fire testing of prototypes began in October 1987. A three-month operational testing phase began in June 1989. On Sept. 5, 1990, the Army awarded the first low-rate initial production contract for 44 vehicles. Initial production models were completed in April 1992. Two low-rate production contracts for 60 vehicles each followed. FMC Corp. was selected for full-rate production in April 1993 and received a $30.5 million contract to upgrade 60 M109s to the A6 configuration. A complete batch of 630 systems was to be upgraded by October 1998. Options for another 83 systems were exercised, bringing the total contract value to $376 million. In April 1997, the Army ordered 37 additional M109A6 systems from United Defense. An option for another 36 systems was exercised in November 1997, bringing the total to 950 units, with deliveries wrapping up in June 1999. In mid-2000, the Army ordered another seven M109A6s for the National Guard under an $8.3 million contract. Deliveries were concluded in January 2002. Another 18 vehicles were ordered under the deal, bringing its value to $21.2 million and increasing the number of operational M109A6s to 975.

Other improvements included secure SINCGARS radios, the Paladin digital fire-control system (PDFCS), onboard diagnostic systems, increased ammunition load, additional armor and upgraded engine and transmission.


This was a West German development first fielded in 1964. Rheinmetall-designed horizontal sliding-wedge breechblock, different muzzle brake and a different fire-control system. Barrel length is 14 ft 6 in (4.422 m); weight complete is 4,224 lb (1,916 kg), of lining, 2,072 lb (940 kg); barrel chamber volume is 823 cu in (13.489 liters); and 22.75-ton (3,200-bar) recoil force. Max recoil length is 32 in (815 mm) in 0-41 deg elevation, decreasing to 18.3 in (465 mm) by 51.2 deg elevation.

Maximum range is increased to 20,165 yds (18,500 m). Two three-barreled smoke dischargers are mounted on the turret.


This is a German update that overhauls the basic design and upgrades many systems. The original M109G gun is replaced by Rheinmetall 39-caliber gun with a range of 27,012 yd (24,700 m). The turret bustle is modified to hold 22 projectiles and can be reloaded through two outward opening doors. Another 12 rounds are stowed in the hull. New provisions are made for propellant charge stowage. Other changes include door locks, blast cover for the panoramic sight and new sealing for the shields. A hand-drive mechanism is provided for the traversing gear and new elevation balancing cylinders are provided.

The vehicle features a new 155-mm barrel clamp, revised ventilators, new air-filter system, new instrument layout for the driver, turbo-supercharger system, reinforced torsion bars on the suspension and a driver's hatch lock. The powerpack has been altered to simplify replacement.

The gun has a new flexible bellows, fume extractor, modified obturation system, breech ring, buffer and muzzle brake. Barrel weight increased to 5,247 lb (2,380 kg) for complete assembly, 3,131 lb (1,420 kg) for inner liner. Barrel chamber volume increased to 1,150 cu in (18.845 liters). Barrel length up to 22 ft 10 in (6.96 m). The A3G can fire NATO and FH70 ammunition, achieving 2,713 fps (827 mps) with latter.

Rheinmetall is prime contractor; refitting at 860 Army Maintenance Depot in St. Wendel, Germany.


Virtually identical to M109A3G, this is a Norwegian upgrade program in which Norsk Forsvarsteknologi (NFT) at Narvik, Norway, performs all upgrade steps except for fitting of new cannon. First contract was in June 1986.


This variant achieved initial operational capability in 1989. The first batch of 32 M109Ls was delivered in 1986 and deliveries were completed in 1992. Italian contractor was Oto Melara. Vehicle weight is 54,675 lb (24,800 kg). It replaced an original locally produced howitzer in 220 vehicles with 39-caliber weapon internally similar to the FH-70/SP-70 project. Refit required few changes to the existing M109 mount. The gun is fitted with an M109G-type muzzle brake. Maximum range for an HE projectile is 26,246 yds (24,000 m) or 32,808 (30,000 m) for a HERA projectile.

The M109L is being replaced in Italian service by the PzH 2000 .

Panzerhaubitze (PzHb) 74, 66/74, 79 and Bison

PzHb66 denoted 140 M109s purchased in 1968 with the short barrel; PzHb74s are 120 M109A1s fitted with the M185 howitzer; PzHb66/74s are PzHb66s refitted with the longer gun; PzHb79 is the designation for 200 M109A1s procured in 1979.

Bison was a proposed Swiss modification that includes an indigenously developed gun with a 47-caliber barrel, a muzzle brake and a flick rammer for a higher rate of fire. It has a range of approximately 16.8 mi (27 km). Four rounds can be fired in 20 seconds. A bustle compartment has been added to increase stowage to 42 rounds. The vehicle has wider tracks and smoke dischargers. Applique armor has also been added. A 52-cal Bison variant is being emplaced in fixed positions.

Pz Hb 88/95

Also known as the M109L47, this upgrade from RUAG Land Systems completed verification trials in 1994. A total of 348 Swiss army M109A1s were upgraded to this standard between 1995 and 2004.

The modular upgrade can be acquired in stages covering firepower and survivability enhancements, as well as reliability and maintainability. RUAG offers refurbishment of the standard 39-cal ordnance or replacement with a new 155-mm/47-cal gun with a fume extractor and double-baffle muzzle brake, as well as 60-groove rifling and chrome plating.

A new bustle-mounted stowage system adds space for 12 additional projectiles and up to 64 propellant containers. Access is through a sliding door from the crew compartment. Attached to the right side of the gun is a charge-standby magazine for temporary storage of four prepared charges. A semi-automatic loader is also fitted. This enables a burst rate of fire of three rounds in 16 seconds or sustained rate of six rounds per minute for two minutes.

Swiss army Pz Hb 88/95s are equipped with a navigation and positioning system. This can accept a ring laser gyro for increased accuracy. The standard system includes a GPS receiver, gunner's control and display unit, travel lock sensor, vehicle motion sensor, driver's display unit and dynamic reference unit. This allows nearly autonomous operation and reduces target acquisition errors.

A new 24-volt electrical system is installed to provide sufficient power for sustained operations on a 24-hour basis.


Under a September 1995, $7.3 million contract with Barnes and Reineke, Spain's entire fleet of M109s was upgraded to this variant, which is unique to Spain.

The M109A5E is nearly identical to the M109A5. It has a digital navigation aiming and pointing system (DINAPS), which combines a hybrid (inertial and global positioning system) navigation system, muzzle-velocity radar and navigation and ballistic software that can connect to the Spanish army command-and-control system.

The system uses the NATO ballistic kernel (NABK) as a core for ballistics using a variety of projectiles to engage stationary and moving targets with a high first-round hit probability.

An automatic gun-laying system (AGLS) is fitted and can be used in conjunction with the DINAPS for to automatically lay the weapon on the target. When fitted with the DINAPS and AGLS, an M109A5E can come into action, fire 15 rounds and move to a new position in nine minutes.


Rheinmetall DeTec announced this new variant in 2004. The M109 L52 utilizes the 155-mm 52-caliber cannon of the PzH 2000 self-propelled howitzer. According to a Rheinmetall DeTec June 14, 2004, press release, the M109 L52 "is capable of rapid deployment and autonomous operation in a wide spectrum of tactical scenarios. In the top-of-the-line configuration, the M109 L52 is fully able to perform "shoot and scoot" missions." The layout is virtually identical to the standard production model.

Due to different customer requirements, Rheinmetall has developed three different levels for the M109L52 upgrade. Level 1 is the baseline model with the 155-mm/52-cal barrel with standard PzH 2000 muzzle brake and bore evacuator, new breech actuator system, modified cradle, new gun mount, turret modifications, new elevating and balancing cylinder, hydraulic system improvements, new accumulators and some hill and suspension modifications.

The 155-mm barrel is available with a rotating or wedge-type breech mechanism. The main gun can use conventional bagged charges or Rheinmetall's modular charge system. The 52-cal gun can accommodate six MCS charges.

The Level 2 upgrade features the Selex Sensors and Airborne Systems laser inertial artillery pointing system (LINAPS), a muzzle-velocity radar mounted over the rear of the gun, auxiliary power unit, onboard fire-control and computing system, rammer, new ammunition stowage boxes, ammunition handling kit (AHK) and a remote travel lock. The APU allows all systems to be run with the main engine off. The remote travel lock allows the driver to remain under armor when the gun comes into action. The rammer increases the rate of fire and reduces crew fatigue.

The Level 3 configuration has all of the Level 1 and 2 features, as well as a digital communications system, primer magazine, new firing magazine, AHK and automatic gun laying. It can conduct onboard ballistic computation and shoot-and-scoot missions. According to Rheinmetall, the Level 3 vehicle can stop, fire a six-round burst and move to a new position in under three minutes. The howitzer has a burst rate of fire of six rounds per minute and a sustained rate of three rounds per minute.

A driveline upgrade could be added to the Level 3 configuration, including a more powerful 450-hp diesel engine in place of the 405-hp Detroit Diesel Model 8V-71T.

Other options include laser rangefinder, integrated gun temperature sensor, battle management system, digital crew intercom system, new driver's passive night driving device, air-conditioning, track side skirts, dust cover/filters, NBC protection, laser warning system, 76-mm smoke-grenade launchers, fire/explosion detection and suppression system, and an automatic fuze setter. Additional armor may also be fitted to the hull and turret for increased protection against small-arms fire and mines.

As of the latest update, no sales have been reported.

M109A50e (Austria)

This is an Austrian variant of the M109. Fifty-four of the vehicles were ordered in early 1995 under a $48.6 million contract. The first vehicle was rolled out on May 6, 1997, and deliveries continued at a rate of six per month.

The M109A50e features an Austrian semi-automatic flick rammer, inertial positive navigation system, Swiss electrical system and the M284 cannon in an M182 mount.

Rechenstellenpanzer (ReStPz M109)

This is an Austrian artillery fire-control vehicle with a crew of six. The turret is retained, though the 155-mm barrel is removed to provide greater internal volume.

Onboard equipment includes an artillery tactical computer with printer, KFF-33F-0 radio set and a 28-volt SD/43 A generator. On each side of the turret are three 80-mm electrically operated smoke-grenade launchers. A .50-cal M2 HB machine gun is mounted on the turret roof.

The Austrian army acquired 19 of these vehicles.

Denel Land Systems M109 upgrade

The United Arab Emirates began modernizing its M109s in 2000 with a new gun laying and navigation/integral gun fire-control system from Denel Land Systems in South Africa. Other improvements included a remote-operated barrel clamp, semi-automatic hydraulic push rammer, auxiliary power unit and air-conditioning system.

M109A6 Paladin Integrated Management (PIM)

The latest variant for the U.S. Army, PIM integrates an upgraded M109A6 turret with a brand new chassis from BAE Systems. The program, launched in late 2007, was developed to address the long-term viability and sustainability of the vehicle and maximize commonality across heavy brigade combat teams (HBCTs).

The new all-welded aluminum armor chassis incorporates a Cummins 600-hp diesel engine and L-3 Combat Propulsion Systems HMPT-500 series automatic transmission. The new powerpack will improve the power-to-weight ratio and top speed of the M109A6 PIM.

The vehicle utilizes the final drives, torsion bars, road wheels, road arms and track from the Bradley infantry fighting vehicle. The upgraded electrical system includes a 70-kW generator. A health and usage monitoring system (HUMS) will be installed as standard. New in-arm rotary dampers are also fitted.

The chassis is longer than the original M109 providing greater internal volume. The M109A6 PIM can carry 43 155-mm projectiles, including 17 M982 Excalibur precision-guided rounds. The chassis is expected to increase total weight by about 5 percent with additional growth potential built in, according to BAE Systems.

The driver is provided with cameras for improved situational awareness to the front and rear.

The existing M109A6 turret is enhanced with a semi-automatic rammer and all-electric drives from the now-cancelled Non-Line-of-Sight Cannon (NLOS-C ). Shells will still have to be hand loaded. The crew is provided with individual spot cooling as well as standard cooling vests for operations in hot temperatures. The electric gun, ammunition handling components and air-conditioning system will be powered by the BAE Systems common modular power system (CMPS). This provides 47 hp (35 kW) of 600-volt direct current, which can be used for voltage conversion and can support other power loads required within the Paladin platform.

The PIM turret rotates 80 deg left or right from center because of the new power system. The PIM vehicle has a pivot-steer function so that when targets are beyond the traverse limit, the vehicle can slew to that target as fast as the original system could traverse its turret. The Paladin's slip ring, which serves as an electrical contact between the chassis and the cab, is replaced with a cable management power system.

A prototype was fitted with an integrated protection system for the commander that provides lateral protection when using the .50-cal M2 heavy-barrel machine gun.

The PIM vehicle uses Bradley road arm assemblies, torsion bars and idler assemblies and has six roadwheel stations compared to the seven on previous vehicles. New double-pin, double-block 19.1-in (485-mm) wide XT-161 tracks replace the 14-in (356-mm) tracks on legacy vehicles. This has significantly reduced ground pressure and increased the vehicle's mobility, especially in sandy terrain, BAE officials said.

The existing 155-mm/39-cal M284 gun is retained. A new digital fire-control system is installed and the modular artillery charge system (MACS) will replace bag-type charges. The M109A6 PIM can carry up to 42 conventional 155-mm rounds and nine Excalibur rounds. It can fire the latter 25 mi (40 km) and conventional rounds about 19 mi (30 km). The PIM can fire four rounds per minute for three minutes and then one round per minute, according to BAE Systems officials. The howitzer does not have a multiple round simultaneous impact (MRSI) capability because firing multiple rounds too quickly can overheat the tube.

Industriewerke Saar (IWS) power pack upgrade

Procured by the United Arab Emirates for its M109L47 vehicles, this consists of a Deutz BF6M 1015 CP six-cylinder air-cooled diesel developing 442 hp (330 kW) coupled to an Allison XTG-411-4 automatic transmission with four forward and two reverse gears. The U.A.E. ordered 85 units with deliveries completed in 2005.

Other Designations

As the M109 has been exported to a myriad of foreign clients, there are several designations associated with this system. Some of the more well-known ones are as follows:

M992 Field Artillery Ammunition Support Vehicle (FAASV)

Resupply vehicle created by substituting a covered superstructure for the M109 turret. See separate database entry.


The U.S. Army's displeasure with BMY's management of the HIP program was underscored by an October 1990 report that the Army planned to move M109A6 production from BMY's York, Pa., plant after the first 100 vehicles were completed. The Army would then stage a competition for later production or produce the A6 in one of its own depots (e.g., Letterkenny Depot in Chambersburg, Pa.). Letterkenny was later used to produce support components for the Paladin and to recover parts from vehicles being scrapped.

On Sept. 27, 1991, President George Bush announced that all ground-launched tactical nuclear weapons, including the M454 155-mm projectile with W48 0.1-kt yield warhead, would be eliminated from the U.S. inventory as soon as possible.

Criticism of the M109 continued after the 1991 Persian Gulf War. The low-range and somewhat slow speed of the vehicles in actual combat conditions led to the creation of the Crusader program, which was expected to eventually replace the M109 in U.S. service. However, with Crusader 's cancellation in 2002, the Pentagon has started to look hard at other replacements for the aging M109, including non-conventional concepts.


The M109 saw service with the United States Army in the Vietnam War.

More than 500 U.S. and British M109s (including 24 Marine Corps vehicles) were sent to Saudi Arabia beginning in August 1990 as part of the Persian Gulf War.

An outline of U.S. artillery and MLRS action by the U.S. Army's Directorate of Combat Developments was published in the May 1991 edition of Armed Forces Journal International. Although the report focused on the MLRS, some observations about the M109 were also made. For example, the M185 howitzer's relatively short range put the Iraqi artillery out of reach of all but full-charge or rocket-assisted projectiles during the pre-ground war bombardment phase. On the other hand, 155-mm DPICM munitions proved very effective against Iraqi artillery, especially when fired together with MLRS batteries. Seventy percent of the rounds fired by the 1st Cavalry Division's artillery were DPICM. The relatively few (90) Copperhead projectiles fired reflected the fire support vehicle's difficulties in keeping up with the advance.

British 155-mm howitzers (most or all of them M109s) fired approximately 10,000 rounds during preparations for the ground war and the ground war itself. In addition, Saudi M109s supported the U.S. Marine Corps-Saudi offensive into eastern Kuwait.

The U.S. deployed M109 howitzers to Iraq in 2003.


In FY1998, the per-unit cost of a M109A6 Paladin was $1.624 million.

LATEST UPDATE: 1 November 2011