|Manufacturer:||BAE Systems Land and Armament|
|Product type:||Armoured Vehicles|
Future US Army requirements for new heavy artillery emphasised air transportability, time into and out of action, common parts and interchangeability area of fire. A feasibility study encompassing these requirements was carried out, presented and approved at a meeting held in January 1956. The Pacific Car and Foundry Company (which subsequently became PCF Defense Industries) submitted a concept study for a new family of self-propelled weapons and was subsequently awarded a contract for the design, development and construction of six prototype vehicles: two 175 mm self-propelled guns designated the T235, three 203 mm (8 in) self-propelled howitzers designated the T236 and one 155 mm self-propelled gun designated the T245.
Major design features included the interchangeability of the 175 mm gun in howitzer and 155 mm gun in a common mount, on a common chassis; use of 175 mm howitzer and 155 mm gun field pieces and portions of the M17 standard mount; and drastic reductions in the weight over conventional equipment which was made possible through a new hydraulic lockout system.
The chassis was also considered suitable for use as a light recovery vehicle and, in 1957, the programme was expanded to include both armoured (T120) and unarmoured (T119 and T121) recovery vehicles.
Ordnance service tests with the first prototype chassis began late in 1958. In 1959, a policy was established that diesel rather than petrol engines would be used for future vehicles and three of the prototypes, the T235, T236 and T120, were retrofitted with Detroit Diesel diesel engines and designated the T235E1, T236E1 and the T120E1. Trials of the T235E1 and T236E1 were completed early in 1961 and, in March 1961, both vehicles were standardised, the T235E1 as the M107 and the T236E1 as the M110. The T120E1 was subsequently standardised as the M578 ARV but the T245, T119 and T120 were not developed further.
In June 1961, the Pacific Car and Foundry Company was awarded an initial production contract for both the M107 and M110. First production vehicles were completed in 1962 and the first M107 battalion was formed at Fort Sill in January 1963. Production of the M107 was also undertaken at a later date by the FMC Corporation of San José and Bowen-McLaughlin-York (BMY) of York, Pennsylvania, (both companies subsequently merged to become United Defense LP) with the first production model coming off the York line in 1965. Production was completed in May 1980, by which time 524 units had been completed by BMY. Today, United Defense is called BAE Systems, Ground Systems.
In the US Army M107s were deployed in battalions of 12 guns, held at corps level. All M107s in the US Army and Marine Corps were converted to M110A2s by 1981 and other countries have converted their M107s to the M110A2 configuration. Most countries have now replaced their M107 and M110 system with the Lockheed Martin Missiles and Fire Control, Multiple Launch Rocket System.
A list of arms transfers issued by the United Nations for the period 1992 to 1998 shows that no surplus M107s were exported by any country between these years.
The M107 is operated by a team of 13, of which the (commander, driver and three gunners) are carried on the gun, with the rest in the now BAE Systems, Ground Systems M548 unarmoured tracked cargo carrier, which also carries the ammunition.
The hull of the M107 is identical to that of the M110 and is made of all-welded cast armour and high-tensile alloy steel, with the driver at the front of the hull on the left, the power pack to his right and the main 203 mm armament at the rear.
The driver, who is the only member of the crew seated under armour, has a single-piece hatch cover in front of which are three M17 day periscopes. The middle M17 day periscope can be replaced by a passive periscope for driving at night. The Detroit Diesel 8V-71T engine is coupled to the Allison Transmission XTG-411-2A cross-drive transmission which is at the front of the hull.
The torsion bar suspension either side consists of five dual rubber-tyred road wheels with the drive sprocket at the front and the fifth road wheel acting as the idler. There are no track-return rollers. Attached to each road wheel arm is a hydraulic cylinder, which serves as a shock-absorber, a hydraulic bump stop and a suspension lockout that transmits recoil shock directly to the ground. The tracks are of the single-pin type with removable rubber pads.
The M107 has infra-red night vision equipment but does not have an NBC system or any amphibious capability. In most countries passive (image intensification or thermal) night vision equipment has replaced the infra-red equipment.
The M107 is armed with a 175 mm M113 gun (development designation T256E3) in mount M158, and has an elevation of +65°, a depression of -2° and a traverse of 30° left and right. Elevation, depression and traverse are all hydraulic, with manual controls available for emergency use. The gun has a hydropneumatic recoil system, minimum recoil being 0.711 m and maximum recoil 1.778 m. The breech block is of the Welin-step thread type with a percussion firing mechanism. Mounted at the rear of the vehicle on the left side is a rammer and loader assembly which lifts a 175 mm projectile from the rear or left side of the vehicle, positions and rams it into the chamber. Power for operating this system is obtained from the vehicle's hydraulic system but it can also be operated by handcranks.
The 175 mm gun M113 only fires an HE projectile M437A2 or M437A1. The projectile weighs 66.78 kg, with the M437A1 containing 13.6 kg of TNT and the M437A2 containing 14.96 kg of Composition B.
The M107 could fire the former Space Research Corporation ERSC Mk 7 MOD 7 projectile to a maximum range of 40,000 m. This was not, however, adopted by the US Army, although it has been used by Israel. Production of this round was completed by the Space Research Corporation many years ago and the company no longer exists.
The 175 mm ammunition used by the M107 is the separate loading type; two rounds are carried on the vehicle and the rest in the supporting the now BAE Systems, Ground Systems M548 unarmoured tracked cargo vehicle. The normal rate of fire is one round every 2 minutes but 2 rds/min can be fired for short periods. When travelling, the barrel is retracted slightly to the rear to reduce the overall length of the complete vehicle. Mounted at the rear of the chassis is a large hydraulically operated spade, which is positioned before firing begins.
Fire-control equipment includes a panoramic sight M115 on mount M137 (magnification of ×4 and a 10° field of view), elevation quadrant M15, gunner's quadrant M1A1 and direct fire telescope M116C on mount M138 (magnification of ×3 and 13° field of view).
There are no variants of the M107 although the M110 8 in (203 mm) self-propelled howitzer and the M578 ARV use the same chassis as the M107. The Israel Defence Force calls its 175 mm M107s the Romach.