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Guided mortar rounds have 20-kilometer range

Feb. 2, 2013 - 02:40PM   |   Last Updated: Feb. 2, 2013 - 02:40PM  |  
Marines operate the Expeditionary Fire Support System in May during an exercise in Jordan. Procurement officials aim to double the range of the 120 mm towed mortar system with a new round called the Precision Extended Range Munition.
Marines operate the Expeditionary Fire Support System in May during an exercise in Jordan. Procurement officials aim to double the range of the 120 mm towed mortar system with a new round called the Precision Extended Range Munition. (Staff Sgt. Robert Fisher / Marine Corps)
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Marines who operate the Corps' new Expeditionary Fire Support System will soon have a new guided mortar round that promises to increase accuracy and double the range.

Industry experts say the new 120mm Precision Extended Range Munition, or PERM, should be fielded to units in as little as two years.

Raytheon Co. announced Jan. 22 it has received a contract to provide functioning PERM rounds for live-fire testing within 18 months, making them the second company to enter the Marine Corps' design competition. Alliant Techsystems Inc. also has been tapped to compete for the final design. Marine officials will select the better of the two, and PERM could be hitting targets in the war zone by 2015, according to industry sources.

The system's existing rounds have a range of five to eight kilometers. PERM rounds are expected to reach up to 20 kilometers — the key to that being their ability to correct during flight.

"I liken this to a golf shot," said Michael Means, business development lead for Raytheon's PERM program. "If you hit a shot and it is windy, it is going to affect the trajectory of that ball and you have to compensate for it. This applies to a ballistic mortar, too. … So the crew would try to compensate for that with their gun alignment, and if their gun alignment was off that would add to their margin of error."

PERM takes the guesswork out and helps negate minor errors by using preprogrammed GPS coordinates to guide itself to within a meter or two of a target. Raytheon's entry uses tail fins for stabilization and flaps — technically called canards — near the nose that allow the round to make constant corrections after leaving a mortar tube.

That will make EFSS far deadlier on the battlefield. Introduced in 2009, the system consists of two highly mobile vehicles that can fit inside an MV-22 Osprey or a CH-53E Super Stallion. One pulls an M327 120mm mortar tube, and the other a trailer of ammunition.

Lighter and safer

The new round will reduce the resupply burden, Means said, at a time when leaders are placing a premium on lightening the force. Greater accuracy means Marines can take out a target with fewer rounds, thus reducing the need for ammunition resupply.

"Precision to the Marines is a big deal when you talk about expeditionary missions," Means said. "Having fewer rounds to accomplish the mission is a major deal. If they can accomplish it with one or two rounds, … that is a huge logistics benefit."

And the new round should require little new training. The company took great pains to keep the design simple, shying away from rocket motors that would make the round more expensive and more dangerous.

A defective rocket, for example, could cause a catastrophic explosion in the tube that would likely injure or kill mortarmen. And forgoing a rocket also keeps the round light, so it can be handled by a single Marine, unlike PERM's big 155mm cousin Excalibur.

Excalibur is a guided round for the Marine Corps' M777 howitzers, which set a record the first time Marines used it in Afghanistan in June 2012 by hitting a target 36 kilometers away. But weighing about 100 pounds, it often takes two Marines to wrangle. PERM will weigh at most a pound or two more than a conventional round — about 35 pounds.

PERM's explosive power should be comparable to the system's existing M1101 round. Though it could be slightly weaker to accommodate the guidance system without increasing overall weight, PERM will bring more force to bear on a target because it descends at such a sharp angle, said Rick Williams, Raytheon's program manager for PERM.

Standard rounds can come in at a 45 degree angle, especially at long ranges. When they detonate, the top half of the round blows straight up into the air, he said. PERM rounds, however, are likely to place more energy and fragmentation directly on a target.

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