Saudi Arabia has purchased 180 older American M109A5 and M109A6 155mm self-propelled artillery vehicles for conversion/upgrade/refurbishment, in Saudi Arabia, to 177 M109A6 versions with all the latest updates and modifications. All this will cost about $7.4 million per converted vehicle. Saudi Arabia will be the only foreign user of the M109A6 and the only other user besides the United States.
Meanwhile the U.S. Army is finally starting to produce large quantities of the M109A7, an even more extensive upgrade of the M109A5. The M109A7 would have been about twice as expensive and the Saudis decided that the long used and well tested M109A6 was adequate to their needs, especially since their M109A6s would be customized to perform in very hot and very dusty Saudi Arabia with modifications that were well proven in other American armored vehicles.
The M109A6 is a 28 ton tracked armored vehicle that carries a 155mm gun that can fire shells up to 30 kilometers. This version of the M109 has the latest GPS navigation and fire control systems that enables the vehicle to halt and open fire in 30 seconds at distant targets whose precise locations were received and entered into the fire control system while the vehicle was moving. The Saudis can use GPS guided shells that enable their M109s to halt, fire several GPS guided shells and then be on the move again (at up to 56 kilometers an hour) in less than two minutes. The crew of five is adequate to operate the gun as well as perform all regular maintenance. The M109A6 carries 39 rounds with it and using the ATK GPS fuze system (it is screwed into the front of the shell in place of the normal fuze) those 39 guided rounds can do as much damage as ten times as many unguided shells would do. This maks the 177 Saudi M109A6 vehicles a formidable artillery force.
Meanwhile in 2018 the U.S. Army was finally allowed to put the latest M109 version, the M109A7, into full production, with an initial order of 48 vehicles. Back in 2013 the first M109A7s appeared as part of low-rate initial production. Before that there were only prototypes. The 2013 decision produced 18 of the 27 ton M109A7 vehicles, along with 18 of the 26 ton armored M992 CAT (Carrier, Ammunition, Tracked) ammunition carrier vehicles. These carry 90 rounds each (the M109A7 carries 39) and have a crew of 3. Each pair of vehicles cost about $14.5 million. Originally known as the M109 PIM (Paladin Integrated Management program) when it began testing in 2011 it was renamed M109A7 when the years of testing and revisions produced a stable design. The M109A7 is supposed to eventually replace current M109A5 and M109A6 models used by the U.S. Army.
Despite the popularity of the M109, this design is from the late 1950s and the U.S. Army has long been seeking a replacement, without much luck. For example, in 2009, the army cancelled its second attempt (the XM1203 NLOS-C) at creating an M109 replacement. The third attempt was the M109A7/PIM. The idea behind PIM was for the army to rebuild about 60 percent of its existing 900 M109s, rather than trying to come up with another new design. But PIM is quite an extensive upgrade. It uses many engine and drive train components used by the M2 Bradley infantry vehicle and a new engine control system. These new components are more efficient and the makes the M109 easier to maintain and supply with replacement parts. This use of M2 vehicle components made the M109A7 capable oh handling more weight (up to 34 tons for the combat ready vehicle).
The cab and gun mounts from the Paladin remain largely unchanged. From the XM1203, the automatic rammer, but not the automatic loader, is used. So troops will still have to manually load the propellant and 41 kg (90 pound) shell but the semi-automatic rammer will then push the propellant and shell into the firing chamber and close the breech. Automating this part of the process improves accuracy somewhat because when troops manually shoved (rammed) in the propellant and shell, they often applied too much, or too little, pressure and left the shell out of position by a tiny bit, just enough to hurt accuracy. Of course that is not a problem when using the GPS guided shells. PIM includes new electronics and numerous small improvements, many based on user suggestions. This makes the M109A7/PIM competitive with some new European self-propelled 155mm howitzers.
The NLOS-C was to have been the first of the eight revolutionary MGV (Manned Ground Vehicle) systems to enter service in 2009, as part of the FCS (Future Combat System) program. But the FCS lost its focus, budget discipline, and Congressional support. It was cancelled in 2009. Before that the prototype NLOS-C was cobbled together in 6 months in 2002, after the new (and very high tech and high priced) Crusader SP artillery system was cancelled. The 45 ton Crusader used an autoloader and an engine similar to the one used in the M-1 tank. With the end of the Cold War in 1991, Crusader was eventually deemed too heavy and too expensive. The NLOS-C used some Crusader components but was closer in size to the M109 without being enough of an improvement to justify the cost.
Although the M109 has been frequently updated, the NLOS-C incorporated many more new technologies. This included an auto-loader (from the Crusader) and a more modern 155mm gun and an APC chassis with a hybrid-electric engine (to reduce fuel consumption). This all weighed 23 tons and the NLOS only had a 2 man crew, compared to 5 in the M109.
The final version of the NLOS-C was to be heavier (about 27 tons) because more defensive systems were added, to reflect experience in Iraq. The NLOC-C also got a lot of new electronics. The vehicle carried 24 rounds of 155mm ammo. Congress originally demanded that NLOS-C be in service by 2008, but development needed a few more years. Field testing (operating as one would in combat) began in 2007 using the 6 prototypes.
One problem that quickly appeared was the inability of the 2 man crew to hold up during 24/7 operations. The then current M109A6 had enough people (five) to take care of maintenance, standing guard, and, basically, always having 1 or 2 people rested and alert. Not so easy when you only have two guys. One solution was to have two or more crews per vehicle, as combat aircraft (and some warships) have done for years. The off-duty crews would be back with the support troops. PIM was designed to operate with a crew of 4, compared to 5 in the M109A6 and earlier models. But it quickly became apparent that a five man crew was more practical because of the need to effectively deal with the typical workload encountered when in a combat zone.
One of the things that helped kill the NLOS-C was the new GPS guided Excalibur shell and even cheaper ATK fuzes that added GPS to any shell. The forst smart shell entered service in 2007 and changed everything. Excalibur has worked very well in combat, and this is radically changing the way artillery operates. Excalibur or ATK means 80-90 percent less ammo has to be fired, meaning less wear and tear on SP artillery, less time needed for maintenance, and less time spent replenishing ammo supplies and more time being ready for action. Excalibur was followed by the even cheaper ATK fuze that turned an unguided 155mm shell into a GPS guided one.
In the war on terror, even the M109 has not been used much. The lighter, towed, M777 has proved more useful, especially when using the Excalibur shell or ATK fuze. Currently, the army plans to keep the M109A7 around until 2050. The M109 was a solid design, which is pretty clear from how difficult it's been to come up with a replacement. So, in the end, the army replaced the M109 with another M109 upgrade.
The army still plans to acquire over 500 M109A7s, reflecting the impact of the GPS guided shell and the number of older M109s that are still fit for service. Since the late 1990s, because of the growing use of smart bombs and GPS guided rockets and shells, the U.S. Army cut the number of artillery weapons roughly in half. This ends a century of artillery tactics and technology, which featured large scale use of unguided shells fired at targets the gun crews could not see (indirect fire). Such tactics were radical and new a century ago and reached their peak during the World Wars, where individual battles often saw bombardments lasting days and expending millions of shells and rockets. All that is gone now and an era has ended. As good an upgrade as the M109A7 is the Saudis realize that the older M109A6 tec plus guided shells was enough to get the job done.