The U.S. Marine Corps has, as is their custom, taken an innovative approach to developing a new lightweight, self-propelled artillery system (the Expeditionary Fire Support System, or EFSS). They have combined an existing commercial vehicle, the Supacat HMT (High Mobility Transport) with an Israeli 120 mm mortar system. The HMT is a seven ton, four wheel cross country vehicle with a capacity for 3.2 tons. It has a 180 horsepower engine and a 4x4 drive optimized for cross country work. The cab is being modified to hold the five man gun crew. The Israeli mortar system weighs 1.6 tons and is mounted on a computer controlled turntable. The mortar can fire regular 120mm shells 8.2 kilometers, or rocket assisted ones 13 kilometers. This is not as far as a 155mm howitzer can reach, but the marines feel that air power and rockets can handle longer range targets.
The breech loading mortar system allows for rapid fire and the turntable system takes data directly from forward observers and quickly positions the 120mm tube to put the shells on the target. The EFSS can put shells on the target within minutes of a request. The system can fire 20 rounds in two minutes and uses a GPS assisted fire control system to provide accuracy comparable to any other artillery system. The EFSS is light enough to be moved by helicopter or Osprey tilt-wing transport.
The 120mm shells are also about half the weight of 155mm ones. This is to be overcome with a higher rate of fire and the use of several types of cluster bomb shells. One of these, for example, will destroy most armored vehicles, and kill or wound most troops in a 100x100 meter area. Each of the 32 bomblets can penetrate four inches of armor, but will be hitting the thinner top armor on armored vehicles.
The marines went after the 120mm mortar, instead of another 155mm howitzer, because the mortar is lighter, faster firing, more mobile and, with the right ammunition, just as destructive as the larger howitzer.
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