The M102 105mm howitzer is used in air mobile (helicopter) and light infantry operations. The weapon carriage is lightweight welded aluminum, mounted on a variable recoil mechanism. The weapon is manually loaded and positioned, and can be towed by a 2 ton truck or High Mobility Multipurpose Wheeled Vehicle (HMMWV), can be transported by UH-60 Black Hawk helicopters, or can be dropped by parachute with airborne units.

The M102 105mm towed howitzer is a lightweight towed weapon that provides direct support fires to light, airborne and air assault forces. It is nearly three-quarters of a ton lighter than the World War II-era M101A1 105mm towed howitzer that it replaced.

When emplaced, the howitzer’s high volume of fire compensates in large measure for the lower explosive weight of the projectile compared to the 155mm howitzers.

A sustained rate of fire of 3 rounds per minute can be reached with a maximum of 10 rounds per minute for the first three minutes. Range can be increased to 15,100 meters (9.38 miles) with rocket-assisted projectiles.

It has a very low silhouette when firing and a roller tire attached to the trail assembly of the M102 permits the weapon to be rotated 360 degrees around a firing platform, which provides the pivot for the weapon. The weapon can be elevated from -5 degrees to a maximum of 75 degrees. The M102 has been replaced in the active Army by the M119A1 105mm towed howitzer.

The M102 is still found in several Army National Guard units and the Air Force uses the same cannon and recoil system in the AC130 gunship.

Since 1964, the US Army had acquired 1,150 M-102 towed howitzers.

The requirement for a light towed 105 mm howitzer to replace the 105 mm M101 (which is covered in detail in a separate entry) in selected units was issued in 1960. The first prototype was completed at Rock Island Arsenal in 1962 and was type-classified as Standard A in December 1963. First production M102s were completed at Rock Island in December 1965 and the howitzer was first used in combat in South Vietnam the following month. The weapon subsequently underwent major modifications to solve design problems.

Over 1,200 M102s were built by Rock Island Arsenal before production was finally completed in the early 1970s. A further 22 were built for foreign military sales in FY80.

The main advantage of the M102 over the earlier M101 is that it only weighs 1,496 kg compared to 2,258 kg. It can also be traversed rapidly through 360° to engage targets in other sectors.

In 1985, the US Army had 526 M102 howitzers in its inventory. The M102 has been replaced in front line service by the BAE Systems Land Systems 105 mm Light Gun, designated the M119 (L119 in British Army service) in US Army service. The US Army holds quantities of the M102 for overseas sales to authorised countries.

Figures released by the United Nations for the years 1992 to 2006 show that there were no exports of the M102 in this period.

In mid-2004 it was stated that a total of 11 US Army National Guard field artillery battalions still use the 105 mm M102. It is hoped that these will be replaced by an additional buy of the 105 mm M119A2.

The 105 mm howitzer M102 consists of the M137 105 mm cannon, M37 recoil mechanism, M31 carriage and fire-control system.

The two-wheeled box carriage is constructed of aluminium. In the firing position, a circular baseplate is lowered to the ground under the forward part of the carriage and the complete carriage can be quickly swung through 360° by means of a roller located at the rear of the trail assembly. The baseplate is staked to the ground before firing begins. The elevating mechanism utilises a pair of elevating screw assemblies and permits an elevation of +75° and depression of -5°. The variable-length recoil system used on this weapon eliminates the need for a recoil pit.

The fire-control system consists of the M1A2 quadrant, M14A1 quadrant, M113A1 panoramic telescope and an M114A1 elbow telescope. Radioactive light sources are used to illuminate the fire-control system. The tritium light sources are a heavy radioactive isotope of hydrogen gas, sealed in a Pyrex glass container, coated with phosphor. Weapons Command initiated a self-illumination development programme at Frankford Arsenal, Delaware in January 1969, in response to numerous reports of poor instrument light performance in Vietnam. The equipment successfully completed testing in February 1970. Production contracts for the modification kits were awarded in September 1973 and the first kits were issued in 1975.

The M102 fires the same range of ammunition as the M101 but with a slightly higher muzzle velocity and, therefore, a slightly longer range:

• APERS-T (M546) with the complete round weighing 17.35 kg, maximum muzzle velocity of 549 m/s and a maximum range (charge 7) of 12,400 m

• HE (M1) with the complete round weighing 21.06 kg, maximum muzzle velocity of 494 m/s and a maximum range (charge 7) of 11,500 m

• HE (M413) (carries 18 M35 grenades) with the complete round weighing 19.06 kg, maximum muzzle velocity of 494 m/s and a maximum range (charge 7) of 11,500 m

• HE (M444) (carries 18 M39 grenades) with the complete round weighing 19.06 kg, maximum muzzle velocity of 494 m/s and a maximum range (charge 7) of 11,500 m

• HEP (M327) with the complete round weighing 15.27 kg, maximum muzzle velocity of 559 m/s and a maximum range of 8,685 m

• HERA (M548) (RAP) with the complete round weighing 17.46 kg, maximum muzzle velocity of 548 m/s and a maximum range of 15,100 m

• Illuminating (M314 series) with the complete round weighing 21.06 kg, maximum muzzle velocity of 494 m/s and a maximum range (charge 7) of 11,500 m

• Smoke (M60 series) with the complete round weighing 19.46 kg, maximum muzzle velocity of 494 m/s and a maximum range (charge 7) of 11,500 m

• Smoke (M84 series) with the complete round weighing 19.03 kg, maximum muzzle velocity of 494 m/s and a maximum range (charge 7) of 11,500 m

• HE (M760) to a maximum range of 14,000 m