The M106 was a Cold War-era (1947-1991) dedicated mortar carrier of the United States Army before being supplanted by the more modern M1064 series in same battlefield role. The type was built upon the existing - and proven - framework of the classic M113 Armored Personnel Carrier (APC), a ubiquitous tracked system seeing service all over the globe primarily with American allies. The M106, for its part in military history, was featured in the fire-support role, capable of lobbing various 107mm projectiles through Non-Line-of-Sight (NLoS) fire in support of infantry and mechanized ground actions.
The M106 conversion was handled by FMC Corporation of the United States. The vehicles saw combat service in the Vietnam War (1955-1975).
The variant was born through the developmental-minded "XM106" form and entered service as the "M106". The primary change to the M113 was the introduction of a rounded, two-piece roof hatch which sat over the 107mm (4.2") M30 (or Soltam M-65) heavy field mortar at the rear of the vehicle. The mortar sat atop a 90-degree (right and left of centerline) traversing turntable (rear-facing fire) and could be dismounted for use as a standard mortar weapon system as needed. The vehicle's exterior port side hull wall was used to carry the baseplate and bipod support structure for this feature.
Up to 88 x 107mm projectiles could be carried on board the vehicle and this collection amounted to a mix of High-Explosive (HE) shells along with illumination and White Phosphorous (WP) types.
Beyond the 107mm mortar weapon was a single, optional 12.7mm Heavy Machine Gun (HMG) installed at the commander's cupola over the center of the hull roof. This gave the operator complete 360-degree coverage around the vehicle to counter both aerial and lightly-armored threats (as well as infantry). Vision blocks were embedded into the cupola for situational awareness when "buttoned down". Armor protection was of aluminum, suitable against only small arms fire. The vehicle's overall weight reached nearly 13 tons and dimensions included an overall length of 16.2 feet, a width of 9 feet, and a height of 7.3 feet.
Internally, drive power came from the M113's Chrysler gas-powered engine but this changed to a Detroit Diesel 6V53T diesel-fueled engine of 210 horsepower to drive the conventional track-and-wheel arrangement once the M113 line switched to the diesel units. This change then gave rise to the "M106A1" variant in turn. The M106A1's powertrain included the Allison X200-4 series transmission.
All told, the vehicle could range out (on roads) to nearly 290 miles. The track-and-wheel running gear gave it a good steady pace to keep up with accompanying mechanized forces.
M106 total production reached 860 units of which the United States Army procured 589 and 271 being shipped to foreign allies (the series was not widely exported, ending up in the inventories of just Argentina, Greece, and Peru). The follow-up M106A1 was built to the tune of 1,316 units with the U.S. Army taking into inventory 982 and the remaining 334 shipped overseas.
With the M113A2 APC's introduction into service, the M106 line was, again upgraded in turn resulting in the "M106A2" carrying the same improvements and capabilities as the APC form.
The United States no longer operates the M106. The replacement M1064 vehicles entered service in 1990 and have only seen export to ally Lithuania.