| Specifications | |
|---|---|
| Weight | (combat): 28.3 tonnes (62,390 lbs) |
| Length | 6.46 m (21.18 ft) hull 11.30 m (37 ft) overall |
| Width | 3.15 m (10.33 ft) |
| Height | 3.47 m (11.38 ft) |
| Crew | 13 (vehicle capacity 5) |
| | |
| Caliber | 175 millimetres (6.9 in) |
| Elevation | -5° to +65° deg. |
| Traverse | 360° |
| Rate of fire | rapid: 1 rpm, regular: 1/2 rpm |
| Maximum range | 34 kilometres (21 mi) |
| | |
| Primary armament | 1 x 175mm M113 or M113A1 Gun |
| Engine | General Motors 8V71T; 8 cylinder, 2 cycle, vee, supercharged diesel 450 hp |
| Suspension | torsion bar |
| Ground clearance | 44 centimetres (17 in) |
| Operational range | 725 kilometres (450 mi) |
| Speed | 80 kilometres per hour (50 mph) |
The US Military Self-Propelled Gun The M107 175 mm was part of a family of self-propelled artillery that also included the M110. The M110E2 chassis had a Depot Level upgraded chassis and drive train due to the heavier “tube” (E2 barrel). The 175 mm gun was used primarily to attack enemy Command, Control and Communication (C3) and Supply Trains, where its 21 mile performance out ranged any common Soviet produced weapon. The M110 operated separately from the M107, with about half the effective range (even with Rocket Assisted Projectiles, RAP) but nuclear capable requiring different security, personnel in the Nuclear Personnel Reliability Program (PRP) and nuclear ammunition assembly training (N5). The M107 was the last Self Propelled “Gun” (high velocity, low trajectory, long range) in the U.S. Army inventory. The M110 was a “Howitzer” (low velocity, high trajectory, short range). Both weapons have since been replaced by 155 mm weapons like the M109 howitzer, due to the fall of the Soviet Union and a change of Strategy, Tactics, (no more massive enemy tank and artillery units) and the types of conflicts/wars the United States faces (High Intensity, Guerrilla Warfare, requiring Artillery surgical strikes, not massive destruction).Retube
The retube from 175 mm to 8 inch (short tube or long tube) had to be done above the organizational (field) level of maintenance, since the chassis also had to be upgraded. The lowest level of retube was done at the Battalion Maintenance using an overhead rail crane/winch. Retube normally occurred at Ordnance Depot Support Units. Or Depot Level, Anniston, Picatiny, Miesau. The M578 Light Recovery Vehicle was only used to lift the “powerpack” (engine) or final drives (transmission) from the hull, this was done once a month to clean the rubbish from the engine and transmission compartment covered by two aluminum deck plates. The barrels could not be replaced using a single M578 due to weight and the precise placement of the barrel (tube) into the cradle without damaging the barrel brass runners.You had to use two cranes one either end of the tube. The “retubing” from 175 mm to 8 inch was usually accomplished by the Supporting Ordnance Company and required an overhead electric rail winch and chassis modifications for the E2 Barrel. The M578 used the same chassis and drive train components as the M107 and M110.
Chassis
Both the M107 and M110 are based on a common chassis, It features five road wheels on either side of the chassis with idler arms attached to torsion bars, with the track driven from the front by a 450 hp General Motors turbo supercharged diesel, the turbo charger being connected to the supercharger by a steel pencil size “quill” shaft. The engine and transmission mounted in the front right with the driver to its left. The engine had an attached hydraulic pump that was used to traverse the turret with a manual backup hand crank. The hydraulic pump was sometimes mistakenly used improperly to dig in the rear spade resulting in damage to the hydraulic spade cylinders after the first round is fired. The manual backup was used to Lay the Gun since the hydraulic control was too course. The primary purpose of the hydraulic pump was putting the barrel into battery, ramming ammunition and charges, raising or lowering the rear spade, rapid course deflection adjustment by the gunner, rapid course elevation adjustments by the assistant gunner.
Operations
The M107 was deployed during REFORGER Exercises as General Support to the 7th Corps to the front lines to hit way behind enemy lines. Only two rounds are carried with the gun tractor, along with five of the crew of thirteen. Two rounds are fired by the onboard crew of five (Section Chief, Driver, Gunner, Assistant Gunner, Number One (loads primer, hooks up lanyard “pig tail”, pulls lanyard on command)) and the Gun Section moves to avoid counter battery fires and destruction, similar to Sniper Tactics. The rest of the ammunition and crew followed in the M548 Ammunition Carrier based on the M113 chassis and reloads the M107 at a different location from where the Fire Mission occurred. M107 and M110 use the same drive train components as the M578 Recovery Vehicle, and this vehicle has seen wide use in a variety of engineering roles. Early barrels were limited to 300 firings with the maximum Zone 3 propellant, but later examples extended this to between 700 and 1,200 firings with extensive bore scoping by the supporting Ordnance Company.
Performance
The top speed on the speedometer recorded by one M107 driver was 50 mph at Grafenwöhr Training Area, Germany on a tank trail. During REFORGER our Battery outran Canadian Armor Units, MBTs (Main Battle Tanks). In practiced Direct Fire during REFORGER two M107 Gun Sections destroyed one Tank Platoon. This is due to the faster reload time, since the M107 has a larger open working space and not the cramped closed space of a tank or M109. In live Direct Fire at ranges exceeding the 120 mm Tank Guns the M107 could pick off a Tank Company in column formation and move before the Tanks could get within range. The obsolete tanks used at the Grafenwöhr range as targets would get flipped by the near misses. Practiced point of aim was below the front of the target (lead tank). Point of Aim was Point of Impact due to the high velocity of a Gun instead of a Howitzer. Due to the size of the Grafenwöhr Range (normally used for tank gunnery) we could only use a maximum of Zone 2, even with Zone 2, multiple target tanks would get flipped by near misses. Our direct fire training was halted due to complaints of the Range Managers, their targets were either completely destroyed or had to be flipped upright and repositioned, essentially closing the Range until this could be done.
Laying the gun involved skilled minute movements of the entire “piece” and not just traversing the turret. The driver, gunner and Section Chief would communicate with each other, with the gunner using hand signals to the driver looking in the left rear view mirror to move the vehicle left or right by tapping on the steering bar. And the other canoneers setting the collimeter and aiming stacks.
The large scale deployment of Lance Missile Batteries assumed the mission of the M107.
The M107 was also frequently used by Israel in the various Arab-Israeli conflicts. When these guns were outranged by rocket fire from Tyre, they were upgraded with the addition of Extended Range, Full Bore ammunition and new powder supplied by Gerald Bull's Space Research Corp, allowing operations over 50 km with increased accuracy.
The M107 was retired from the US Army in the late 1970s but it continues to see use in many armies around the world.
