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M108

105 mm self-propelled howitzer

M108

The M108 SPH was considered lacking range and lethality and was gradually phased out of service

 
 
Country of origin United States
Entered service 1962
Crew 5 men
Dimensions and weight
Weight 21 t
Length 6.1 m
Width 3.15 m
Height 3.27 m
Armament
Main gun 105 mm
Barrel length 30 calibers
Machine guns 1 x 12.7 mm
Projectile weight 14.9 kg
Maximum firing range 11.2 km
Maximum rate of fire 4 rpm
Elevation range - 6 to + 75 degrees
Traverse range 360 degrees
Ammunition load
Main gun 86 rounds
Machine guns 500 rounds
Mobility
Engine General Motors 8V71T diesel
Engine power 425 hp
Maximum road speed 56 km/h
Range 386 km
Maneuverability
Gradient 60%
Side slope 30%
Vertical step 0.53 m
Trench 1.8 m
Fording 1.1 m
Fording (with preparation) Amphibious

 

   The M108 was first fielded in 1962, as a replacement for the troubled M52 self-propelled howitzer. It was developed from the T195 self-propelled gun testbed, which itself was later further-developed into the 155 mm T196 six months later.

   The M108 was intended to be the short-ranged component of a new generation of US Army self-propelled artillery, alongside (from shortest range to longest) the 155 mm M109, the 203 mm M110, and the 175 mm M107. Though unimpressive compared to the M109, the range of the M108 filled a wide gap between the minimum range of 155 mm self-propelled artillery, and 120 mm mortar carriers.

   Though effective in combat during the Vietnam war, the M108 was considered lacking in lethality compared to larger 155 mm howitzers (despite the fact that 105 mm rounds are comparable in payload to 120 mm mortar rounds, and the aforementioned range gap between these and 155 mm shells), and it was gradually phased out of service from the US military in the early 1970s. The M108s removed from US service were gradually passed on to allies, and replaced by additional M109s in US service.

   The M108 has been operated by USA, Belgium, Brazil, Spain Taiwan, Turkey. The M108 fleets in the militaries of Belgium and USA have both been retired, but as of 2010, this weapon continues to see service in Brazil, Spain, Taiwan, and Turkey.

   The M108's main gun is a rifled 105 mm M103 howitzer, with a tube 30 calibers long, fitted to an M139 mount. It fires a 14.9 kg projectile at 472 m/sec, can elevate and depress to +75 and -6 degrees respectively, and has an effective range of 11.16 km. The M103 fires HE, WP, smoke, and chemical rounds, and also the M67 HEAT round. It can also fire all standard NATO 105 mm rounds, with the exception of rocket-assisted munitions. A 12.7 mm M2HB heavy machine gun is usually fitted to the rooftop skate mount, providing the M108 with some degree of protection against aircraft and enemy personnel. 87 105 mm rounds are carried, along with 600 12.7 mm machine gun rounds.

   The M108's aluminum armor provides sufficient protection from blast overpressure, shell splinters, and small arms fire (up to 12.7 mm AP over the frontal arc), but it has no spall liners or NBC system. Due to its lack of an NBC system, M108 crews must exercise maximum caution when firing chemical rounds, as contamination by their own munitions could result from a headwind from the impact area.

   The chassis of the M108 is flat on all sides, and virtually featureless. The chassis roof is long, with a shallow slope at the front. The front of the hull has a flat, slightly-peaked glacis plate, and a large, square door with right-side hinges is in the center of the rear end. The driver's hatch is on the extreme front-left, is square in shape, and hinged on the left side. The 90-degree hull sides overhang the tracks with a pronounced gap. The turret is horseshoe-shaped, with a steeply-sloped face and sides, and a 90-degree slope on the rear. On each side of the turret is a small, square-shaped door. The turret roof has a small, circular hatch at the extreme front-right, and a round cupola at the rear-left, fitted with a skate mount for a machine gun. The main gun is short, with a conspicuous cylindrical fume extractor behind the muzzle, and a cylindrical mantlet.

   The M108 has a crew of 5 men. The driver's position is in the aforementioned location, while the section chief, gunner, and 2 cannoneers reside in the turret. Crew accommodations are austere, and the M108 does not have an air conditioner or heater as standard equipment.

   The M108 is powered by a Detroit Diesel 8V71T diesel V8, generating 425 hp at 2300 rpm, mated to an Allison XTG-411-2A automatic transmission with 4 forward gears, and 2 reverse gears. 511 liters of fuel are carried, giving the M108 a maximum range of 386 km. With 425 hp driving 21 tonnes, the M108 has a power/weight ratio of 20.32 hp/tonne, and a governed top speed of 56 km/h.

   The M108's suspension is a standard torsion bar system, with 7 individually-sprung roadwheels, and a T136 or T137 track, both with 79 shoes-per-track. The track is a "flat track" type, with no return rollers; the drive sprocket is forward and idler rear. Combined with the vehicle's weight, its track footprint gives the M108 0.69 kg/cm² of ground pressure.

   The M108 is 6.1 m long, 3.15 m wide, 3.27 m tall, has no gun overhang, and weighs 21 tonnes. It can tackle a 60% gradient, a 30% side slope, a 0.53 m vertical obstacle, or a 1.8 m trench. It has 0.45 m of ground clearance, and is amphibious with preparation.

   The M108's unit cost is approximately $244 000, though it is no longer offered. No information is available on the size of its production, though several hundred are still in use today.

 

Variants

 

   M109; the ubiquitous M109 self-propelled howitzer is basically an M108 with a bigger 155 mm gun. There are many variants of the M109, which are too numerous to cover here. Most of the US Army M108 howitzers were converted to the M109 standard;

   M992 FAASV; this is the primary ammunition resupply carrier for the M109, which is developed from the same chassis as used for the M108 and M109.

   XM701; this attempt to develop an infantry fighting vehicle for the US Army (as a contender for the MICV-65 requirement), and is basically a hybrid of the M108/M109 chassis, and the M107/M110 chassis. This project was effectively a disaster, as the ultimate product failed nearly all of its mission-critical design requirements.

 

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Video of the M108 self-propelled howitzer

 
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