M109 First produced in 1963. It had a 155 mm M126 cannon in an M127 mount, and carried 28 rounds of 155 mm ammunition. It was also armed with a .50cal
M2HB machine gun with 500 rounds of ammunition. Easily identified by its short barrel and a double baffle
muzzle brake with a large fume extractor just behind it. Maximum range of 14,600 meters.
M109G in 1982 The
West German army M109s were designated as the M109G, and featured a
breechblock system developed by Rheinmetall extending the effective range to or according to some sources, a new fire control system, and three smoke dischargers mounted on either side of the turret as well. In December 1966, the United States and Norway signed an agreement related to the co-production of the M109G.
M109A1 Fielded in 1973, this modification replaced the M126 cannon with a 39 caliber M185, featuring a longer barrel while increasing maximum range to 18,100 meters.
M109A1B The M109 rebuilt to M109A1 standard.
M109 66/74 The M109 (Pz Hb) 66/74 is a Swiss upgraded M109 (Pz Hb 66) to M109A1B (Pz Hb 74) standard. Switzerland purchased 146 M109 under the armament program 1968, and introduction of the howitzer started in 1971. All vehicles received upgrade to M109A1B (Pz Hb 74) standard and were delivered from May 1977 to February 1979.
M109A2 Incorporated 27
Reliability, Availability, and Maintainability (RAM) mid-life improvements. Most notably, the long barreled 155 mm M185 Cannon in the new M178 gun mount, ballistic protection for the panoramic telescope, counterbalanced travel lock, and the ability to mount the M140 bore sight alignment device. Stowage of 155 mm rounds increased from 28 to 36 rounds; .50cal ammunition remained at 500 rounds. Fielded in 1979.
K55 in 2013 The K55 is a South Korean license produced variant of the M109A2. In the 1960s, the
South Korean Army received
M107 and
M110 from the United States. However, the number of these self-propelled guns was insufficient to counter rapidly-growing North Korean artillery capabilities. In the 1970s, South Korea began mass-producing towed howitzers locally, but intelligence reports of North Korean
170 mm self-propelled artillery forced South Korea to look for a new self-propelled artillery system. The vehicle's name was changed from KM109A2 to K55, originally a code name from the Samsung factory. In November 1990, the United States and South Korea signed an agreement to allow South Korea to supply M109 parts to third parties. In May 1997, during the Security Cooperation Committee held in Washington D.C., South Korea requested that the United States revise the MOU to export complete K55s, originally intended for domestic use only. South Korea was expecting to export 72 K55s and four ammunition support vehicles to Brazil for $160 million over Belgium's offer, but the
United States Department of Defense declined the request to avoid an arms race in the region. In May 1998, the South Korean military began operating a K55 simulator to boost artillery operator training. The simulator took a year and a billion
KRW budget to develop. It is expected to save 150 million KRW per year per device.
M109A3 M109A1s rebuilt to M109A2 standard, also fielded in 1979.
M109A3B M109A1B rebuilt to M109A2 standard.
M109A3G In 1983, the
German Army purchased 586 conversion kits from the FMS Corporation (now Marvin Land Systems) to convert its fleet of M109Gs to the M109A3G standard. This upgraded variant uses a new gun barrel developed by Rheinmetall, giving an extended range of . It also features a new fire-control system, and three forward firing 76 mm smoke grenade launchers on either side of the turret.
M109A3GN operating an M109A3GN during the
Russian invasion of Ukraine Between 1969 and 1971 Norway acquired 126 M109Gs from West Germany. They were then upgraded to the M109A3GN configuration during the latter half of the 1980s.
M109L M109A4 Soon after the adoption of A2/A3 versions, the Division Weapon Support System study was initiated in 1980, which by the end of the decade resulted in the development of several modernization packages. and later adopted as M109A4, initially scheduled for 1985-1987 but actually fielded in 1989 in the
Reserve Component of the US Army. It was fielded in 1991 in much smaller numbers than originally devised due to the
end of the Cold War. It replaced the 155 mm M185 cannon in an M178 mount with a 39-caliber 155 mm M284 cannon in an M182 mount developed for the M109A3E2 (see below), giving the A5 a maximum range of 22,000 meters with unassisted projectiles and 30,000 meters with
rocket-assisted projectile (RAP) rounds. The vehicle can carry 36 complete rounds of ammunition and has a 440 hp engine instead of the standard 405 hp engine.
M109A5+ Various manufacturers have upgraded the fire control and other components of the M109A5. BAE Systems in
York, PA delivered 12 M109A5+ vehicles to Chile in 2011 and 32 M109A5+ vehicles for Brazil in 2016.
M109A6 Paladin Also originating in the Division Weapon Support System study in early 1980s, the Howitzer Improvement Program was devised as a more extensive modernization than the Howitzer Extended Life Program. The vehicle was originally designed as M109A3E2 before being adopted as M109A6 and finally to 1993. The US Army received the last of 950 Paladins it had ordered in June 1999. Seven further Paladins were ordered for the National Guard in July 2000, with an additional eighteen received in January 2002. In May 2022, the US Army began shipping its M109A6 Paladins for refitting to the M109A7 standard in order to begin the process of modernization. Upgraded Swiss PzHb (Panzerhaubitze)74, 79 and 88 (M109A1B) are known as respectively '
PzHb 74/95,
PzHb 79/95 and PzHb 88/95'. • 33 of the 120 PzHb 74 were modernized to the standard PzHb 74/95 KAWEST. • 207 of the 207 PzHb 79 were modernized to the standard PzHb 79/95 KAWEST. • 108 of the 108 PzHb 88 were modernized to the standard PzHb 88/95 KAWEST.
M109A3GNM The latest version in service with the Norwegian Army's
Artilleribataljonen. In 2006, there were 56 M109A3GNs in the Army's inventory, meaning that at least 70 SPGs had been scrapped after the end of the Cold War. 14 of the M109A3GNs received upgrades in 2007, and were designated M109A3GNM. The upgrade includes a new intercom and new navigation and positioning systems. Two M109A3GN howitzers were destroyed and three damaged during the
2022 Russian invasion of Ukraine.
M109 KAWEST WE Improvement of the Swiss Kawest variant, 133 in total were brought up to this standard: • 25 of the 207 PzHb 79/95 were modernized to the standard PzHb KAWEST WE. Those are currently in service. • 108 of the 108 PzHb 88/95 were modernized to the standard PzHb KAWEST WE. The upgrade was performed by Samsung Techwin, and the first vehicle was fielded by the South Korean Army in early 2011. The K55A1 is fitted with the same electronics and fire control system as the K9. The self-propelled gun has significantly enhanced field operability and accuracy through the installation of
Honeywell Aerospace's TALIN 5000 INS (inertial navigation system), a satellite navigation device (GPS), and a speed calibrator. As a result, the vehicle automatically lays the gun in the desired direction and delivers a first round within 45 seconds between stops, or 75 seconds between maneuvers after receiving the shooting specification, which required 2 minutes and 11 minutes, respectively, on the K55. With the help of a new semi-autoloader, while charges are still inserted manually, the howitzer can fire 4 rounds per minute, increased from 2 to 3 rounds per minute. The improved suspension, involving a strut-type hydropneumatic buffer from Mottrol Co, Ltd., along with an enhanced chamber, allowed the vehicle to shoot K307 and K310 ammunition designed for K9 platform without laying spades at a maximum distance of 32 km. An APU (auxiliary power unit) was installed to operate the howitzer without turning on the main engine. The upgrade cost 20% of the K9 Thunder, 800 million KRW, as of 2021.
M109A7 The newest M109 version for U.S. service is the M109A7, formerly known as the M109A6 Paladin Integrated Management (PIM). The M109A7 shares common chassis components with the
Bradley Fighting Vehicle (BFV) such as the engine, transmission, and tracks. This creates commonality with other systems and maximizes cost savings in production, parts inventory, and maintenance personnel. The M109A7's 600-volt onboard power system harnesses technologies originally developed for the
XM1203 non-line-of-sight cannon, including the electric turret drives and electric gun rammer. Prototypes of the vehicle underwent government testing in preparation for a
Low-Rate Initial Production (LRIP) decision. The testing included RAM, mission and ballistic hull and turret testing. The M109A7 was slated to begin LRIP by 2013. The U.S. Army planned on procuring a fleet of 580 sets of M109A7 howitzers and
M992A3 field artillery ammunition supply vehicles. In October 2013, the
Defense Acquisition Board approved the decision to start M109A7 production. The FY 2014 budget called for $340.8 million in Paladin funding, which would be two dozen vehicle sets at $14.4 million per vehicle. The Army plans to buy 133 vehicles, in 66 one-half vehicle sets starting in 2014. One M109A7 howitzer and two supporting M992A3 ammunition carriers will be destroyed during tests. A Full-Rate Production (FRP) decision was planned for February 2017. In October 2013, BAE received a $668 million contract to begin LRIP of the M109A7. The first M109A6 and M992A2 vehicles were rebuilt to M109A7 and M992A3 standards as part of LRIP beginning in summer 2014. LRIP deliveries began in April 2015. The contract for FRP was signed in December 2017, with 48 vehicles slated for construction. The Army plans to upgrade 689 Paladins to A7-standard. The Army is looking to increase the capabilities of the M109A7. By introducing the new XM1113
Rocket-Assisted Projectile (RAP), The Army is working on an autoloader called the Extended Range Cannon Artillery (ERCA) to increase the sustained rate of fire to 6–10 rounds per minute. Another part of the effort is the use of a new supercharged propellant to fire the shells, which required redesigning the howitzer to handle higher pressures. The Army canceled deployment of the ERCA program in March of 2024, citing engineering challenges such as excessive barrel wear.
Hypervelocity projectile (HVP) In January 2016, the U.S. Army test-fired hypervelocity projectiles originally designed for use by
U.S. Navy electromagnetic railguns. They found that they significantly increased the gun's range. The Army is looking into using the M109 Paladin firing the HVP for
ballistic missile defense, as traditional missile interceptors are expensive, and gun-based missile defense used for point defense would use artillery at a much lower cost per round. The HVP is capable of being fired out to from a conventional cannon. It weighs with a flight body containing its guidance and warhead—less powerful, but more agile to hit small, high-speed targets. Modifications will be needed for the Paladin to effectively shoot the HVP, possibly including different propellant to achieve higher velocities, automated reloading systems to fire quickly enough to defeat salvo launches, improved barrel life, and a new fire control and sensor system. During a test of the Air Force's Advanced Battle Management System (ABMS) in September 2020, an HVP fired from an Army Paladin howitzer successfully intercepted a
BQM-167 target drone simulating a
cruise missile. HVP was renamed to gun-launched guided projectile (GLGP), canceled in the 2022 budget, and tests continued in 2023. File:Bae PIM upgrade.jpg|A prototype M109A7 File:M109A7_Self-propelled_Howitzer.jpg|A M109A7 155 mm SPH being tested at Yuma Proving Ground, Arizona
Experimental vehicles P-52 The P-52 was a 52-caliber variant of M109A6 Paladin offered to South Korea by BMY Combat Systems in 1992. It was rejected by South Korea in favor of K9 Thunder. Proposal stage only.
M109L52 Jointly developed by the Dutch firm RDM and the German firm
Rheinmetall, the M109L52 was first revealed in 2002. The main improvement was replacing the M126 series gun with the longer 52-caliber cannon from the
PzH 2000, thus the MTLS ammunition of the PzH 2000 can be used. Improvements to the loading system were also made, resulting in an increased rate of fire from 3 rds/min to 9–10 rds/min, able to be sustained for up to 2 minutes. A total of 35 rounds can be carried.
M109-52 The M109-52 is a 52-caliber variant of M109 developed by BAE Systems by integrating Rheinmetall L52 cannon.
M1299 The M1299 was a prototype
self-propelled howitzer developed by BAE Systems in 2019 under the
Extended Range Cannon Artillery (ERCA) program. It was based on the M109A7, and was primarily designed for the purpose of improving the M109A7's effective range. One battalion of vehicles is planned to begin a year-long operational assessment in 2023. It was expected to be fitted with an
autoloader, which would have increased its rate of fire from 3 to 10 rounds per minute. The M1299 was cancelled in March 2024 due, at least in part, to excessive barrel wear. Advanced ammunition developed for the M1299 will continue development, and the U.S. Army will look for existing alternatives to fulfil its re-evaluated long-range fire support needs. ==Derivatives==