The first M109 was introduced into service in the American Armed Forces in 1963. It has had various upgrades through out the years and was almost removed from service prior to the 1991 Gulf War, when it was questioned if self propelled guns had any place in a modern American Army, as it could not provide the accuracy of missiles, but due to its success in the Gulf War, the M109 was kept in US service.
The M109
It started life as the T196 prototype which went on for field testing in 1959 at Fort Knox. Issues were found with the suspension and when a new NATO STANAG was introduced about what fuels were to be used by AFV‘s, a new diesel engine was fitted and re-designated the T196E1. An order for the vehicle was placed in 1961 with Cadillac Motor Car Division for a limited production at the at the Cleveland Army Tank Plant, which was then extended in 62 & 63, with production at the same plant but with the Chrysler Corporation. It entered US service in 1963 under the designation M109. It used the M126/A1 155mm main gun in the M127 Howitzer Mount and carried 28 rounds.
The M109A1
This model saw the original main gun replaced with the M126A1, which was an increased Cal Length and like all increased length you get a longer range. The A1 now had an effective range of 18100m, an improvement of 3500m over the M109. The M109A1B was a modified export model.
The M109A2
This model entered production with the BMY Combat Systems in 1978, with the US Army taking delivery in 1979. It was fitted with a new M185 main gun and other improvements known as the “incorporated 27 mid-life” which includes:
1. redesigned rammer and improved recoil mechanism,
2. engine operation warning devices,
3. a redesigned hatch and door latches,
4. an improved hydraulic system
5. bustle designed to carry an additional 22 rounds of ammunition
The M109A3
M109A1 upgraded by the Army in their depots with the “incorporated 27 mid-life” upgrades of the A2.
The M109A4
This model saw the introduction of NBC equipment for the crew and modifications to the turret traverse systems of the A2/A3.
The M109A5
These improvements provide the M109A5 with greater range and allow for sustained fire for prolonged periods of time.
The M109A6 Paladin
Developed by the Ground System Division of United Defence LP (now BAE Systems Land and Armaments) entered service in 1994 and by June 1999 the American Army had received 950 of the A6 Paladin's, with an order of 7 more in July 2000 and a further 18 in January 2002 for the National Guard.
The A6 has seen the most upgrades of all the series. This includes increased armour, internal stowage arrangement for ammunition and equipment has been redesigned to be safer, engine and suspension upgrades, and product improvement of the M284 cannon and M182A1 mount. The integration of an inertial navigation system and encrypted digital communication system allow the howitzer to send grid location and altitude to the battery Fire Direction Centre. The battery FDC in turn coordinates fire through a battalion or higher FDC. This allows the battery of M109's to manoeuvre on the battlefield dispersed in pairs, which then stop and fire within 30 seconds and then move on again to its next location between salvo's of the other M109's in the battery and repeat the process. This gives the M109's a high level of protection and survivability as they are not static or fixed positions and subject to incoming fire. This manoeuvre is known as "shoot and scoot".
The A6's M284 is a 155mm cannon mounted on a M182 gun mount. The projectiles it fires have a range of 24km for unassisted rounds or 30km using assisted rounds. It has a maximum firing rate of up to eight rounds a minute and a sustained firing rate of one round every three minutes, which is obtained with an automatic fire control system and an optional full-stroke hydraulic loading system or semi-automatic loading. The crew are protected with an up to date NBC system and the turret is fitted with Kevlar spall suppression lining for additional ballistic protection.
The A6's are powered by a diesel, 440hp, DDEC 8V71T engine from Detroit Diesel Corporation (same engine used on other models, except this one is beefed up!), and an Allison ATD-XTG-411-4 transmission providing 4 forward and 2 reverse gears. The new suspension system is a high-strength torsion bars with high-capacity shock absorbers. These give the A6 a range of 350 km with a maximum road speed of 56 km/h.
The M109 series uses an 8 man crew, Gun Commander, Driver, Gunners and in a accompanying M992 FAASV-5 (Field Artillery Ammunition Supply Vehicle). For close quarter fighting the A6 can carry either a 12.7mm M2 machine gun or grenade launcher, which is mounted on the right hand side of the turret.
In 2005 BAE Systems Land and Armaments started supplying 219 modification kits to the American Army. The kits will allow the Paladins to fire Modular Artillery Charge System (MACS) and the 155mm precision-guided extended-range XM92 Excalibur projectile being developed by Raytheon and Bofors Defence of Sweden (a BAE Systems subsidiary).
The M109's were due to be replaced, but the $11 billion XM2001 Crusader program was cancelled in early May 2002 by United States Secretary of Defence Donald Rumsfeld, as he felt it was not mobile or precise enough.
The M109 series has and still is in service with over 15 other countries, but it is only the American Army who have the A6 Paladin series. The British Army swapped over in 1993 to the AS-90 and several other European countries are in the process of swapping to the German manufactured PzH 2000.
International Operators
M109
Libya - 18
Oman - 15
M109A1
Denmark - 76 upgraded to A3DK
Ethiopia - 17
Greece - 51 A1B
Kuwait - 5 A1B
Peru - 12
Saudi Arabia - 28
Tunisia - 11
Iran - 390
M109A2/A3
Belgium - 127 A2 (of which 64 upgraded to A4BE; all now decommissioned) and 40 A3 (sold to Brazil)
Germany - 570 A3GE A1/A2 (phased out by 1 July 2007, replaced by the PzH 2000
Greece - 84 A2, 50 A3GEA1, 196 A3GEA2 (plus 56 A3GEA2 to be used to upgrade the 50 A3GEA1 to A3GEA2 level)
Egypt - 279 A2
South Korea - 1040 (K55)
Morocco - 84
Norway - 56 A3G (14 upgraded to A3GN, and then 9 of these upgraded to A3GNM to suit the winter climate)
Pakistan - 150 A2
Portugal
Netherlands - 126 A2/90 phased out, largely replaced by the PzH 2000
Brazil - 40 A3 (former Belgian) Brazilian Army
Republic of China (Taiwan) - 225
M109A4
Belgium - 64 A4BE
Canada - 76 A4B+ Phased outfrom the Canadian Forces since 2005, they were used between 1967 to 2005. All vehicle had been modernized to the M109A4B+ SPH standard in 1980s. They were primary used by the 4 Canadian Mechanized Brigade Group in Germany.
M109A5
Egypt - 201
Israel - 600 Doher
Pakistan - 115
Portugal
Thailand - 20
Morocco - 60
Saudi Arabia - 48
Bahrain - 20
Italy - 192
Greece - 12
Spain - 96
M109A6 Paladin
United States - 951
M109 KAWEST
Switzerland
Chile - 48 former Swiss
International Models
Switzerland - The Swiss firm RUAG developed an upgrade package for the Swiss Army.
The KAWEST upgrades included:
A new Swiss-designed L47 155mm main gun with an increased firing range of up to 36 km, a new gun-laying system and more ammunition storage. A reduction in the crew from 8 to 6, is able to fire 3-round bursts within 15 seconds or maintain a constant firing rate of over one round per minute.
Upgraded Swiss PzHb (Panzerhaubitze) 79 and 88 (M109A1) have been redesignated the PzHb 79/95 and PzHb 88/95.
Israel - The IDF took delivery of M109A2's & A3's around 1970 and were designated the Rochev (Rider) and were used in the Yom Kipper War of 1973. The Rochev's were upgraded (except some were kept in the reserve units) by the IDF from 1993 and designated the Doher. Work was completed by 1997.
The Doher upgrades included:
Inertial Navigating System (INS), air filtering system, changes in the driver's panel & cabin and NBC protection added. Additonal MG on the roof, electrical travel lock for the main gun, external generator, commanders hatch can now be secured in a semi open poistion, providing greater situational awareness and protection.
South Korea - Samsung Aerospace Industries (SSA) was the prime contractor for licenced production of 1040 M109A2. Licenced production of the M109A2, also designated the KM109A2, was completed in 1997. Its AKA the K55.
The M992 Field Artillery Ammunition Support Vehicle -
Entering production in 1983, the FAASV is an M109 hull with a rounded structure in place of the turret, which is used to store 93 155 mm projectiles, 99 propellant charges and 104 fuses. When fully loaded it weights just under 26tons. It has a crew of two and can carry 6 further passengers. When re-supplying an M109, the M992 backs up to the rear door and extends its conveyor into the M109 which is used to transfer rounds between each vehicle. It was equipped with a HALON fire suppression system. A total of 664 vehicles were built for the US Army.
The M992A1 & A2 - Under the FAASV HELP (Howitzer Extended Life Program) the M992 saw changes to the propellant storage set up, upgrades to the conveyor system to work with the A6 Paladin and the same improvements to the Paladin’s engine were made to the M992 engine so that it could keep pace with the Paladin. The upgraded vehicle was re-designated the M992A1. 125 were built from scratch.
The A2 was introduced in 1994. It featured a new auxiliary generator, (replacing the existing one) improvements to the engines radiator, the heater & hydraulic reservoir was moved and all the upgrades from HELP were added. All M992’s were upgraded to the A2 by 1999 including 96 new builds. 36 A2 conversion kits were purchased to convert old M109 SPG’s.
In 2005 a new up-powered auxiliary generator was added and a new storage configuration for the Modular Artillery Charge System (MACS), which resulted in the removal of the conveyor.
The M109 series has seen a lot of action:
Vietnam War - It was so successful with the American Army, its lighter version, the M108 was with drawn from service.
IDF - In the 1973 Yom Kippur and in both the 1982 & 2006 Lebanese Wars.
Gulf War - It was used by the American, British, Egyptian and Saudi Arabian Armies in 1991.
2003 invasion of Iraq - By the American Army.