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Further Reading

M224 60mm Lightweight Company Mortar System (LWCMS)

On 19 March 2013, 7 Marines from II Marine Expeditionary Force were killed and another 8 were injured following an incident during a training exercise at Hawthorne Army Depot, Nevada, when an M224A1 mortar they were using exploded. Reports indicated that a round had prematurely detonated in the mortar's cannon. It was also reported that an indefinite moratorium on the weapon's use worldwide, by the Marine Corps and the Army, had been put into place by the Department of Defense while the cause of the accident was investigated.

The M224 Lightweight Company Mortar System (LWCMS) provides the company commander with an indirect-fire weapon. The complete system consists of the following major components: M225 cannon assembly (14.4 lbs), M170 bipod assembly (15.2 lbs), M7 baseplate (14.4 lbs), and M8 auxiliary baseplate (3.6 lbs). The M224 60mm LWCMS is ideally suited to support airborne, air assault, mountain, ranger, special operations forces, and light infantry units. The M224 can be drop fired (conventional mode) or trigger fired (conventional or hand-held mode). The lightweight M8 auxiliary baseplate is used when firing the mortar in the hand-held mode. The improved M224A1 consists of the following components: M225A1 cannon assembly, M170A1 bipod assembly, M7A1 baseplate, M8 auxiliary baseplate, and the M67 sight unit.

The M224 60mm lightweight mortar is a smooth bore, muzzle loading, high-angle-of-fire weapon. The cannon assembly is composed of the barrel, combination base cap, and firing mechanism. The mount consists of a bipod and a base plate, which is provided with screw type elevating and traversing mechanisms to elevate/traverse the mortar. The M64 sight unit is attached to the bipod mount via a standard dovetail. An additional short range sight is attached to the base of the cannon tube for firing the mortar on the move and during assaults. It has a spring-type shock absorber to absorb the shock of recoil in firing.

The M224 replaced the older, World War II-era, M2 and M19 60mm mortars. These weapons only possessed 2,200 yards of effective range. The M224 was designed to fire all types of the older ammunition, but its primary rounds were of the newer, longer-range type. The M224A1 fires the complete family of 60mm ammunition including high-explosive, smoke, illumination, infrared illumination and practice cartridges. With ranges from 70 meters to 3,500 meters, the M224A1 meets lethality, range and weight requirements for light forces.

Mortars can provide a heavy volume of responsive, accurate fire with a variety of ammunition. They are ideal for attacking close in targets, targets on reverse slopes, and those targets in areas difficult to reach with low angle fire. Mortars are particularly effective in providing white phosphorous and illumination support.

Mortars are transported by vehicle, helicopters, or by man pack. Mortars can be man packed in terrain where vehicular support is restricted. However, in a fast moving operation, the mobility of mortars, coupled with their limited range capability, may be a restricting factor. Mortars also have the capability to be fired from a light armored vehicle.

Mortar fires can be massed on a target by the organic unit. However, massing of mortar fires outside the zone of action of the organic unit is difficult due to the limited range of the mortar. Responsiveness is an inherent characteristic of mortars.

The high angle trajectory and long time of flight causes the mortar to be vulnerable to enemy counter fire. Active and passive measures are used to increase survivability. Because ammunition for mortars may have to be man packed, sustainment of mortars may be difficult. So mortars should be employed as an immediately available source of fire support for the infantry commander. Other indirect fire weapons are used when they can achieve the desired results.

In the 1990s, the Infantry Companies in the Marine Corps included a 60mm mortar section that employed 3 mortars. When the mortar section was in general support, it supported all rifle platoons as directed by the company commander. By keeping the section in general support the company commander retained flexibility, ease of coordination of fires, and the ability to mass fires. Direct tactical control of the section remained with the weapons platoon commander. Fires were controlled from the company command post when observation of the entire company zone of action was possible from that position. If not, the mortar section leader manned an observation post to control the fires. General support was the preferred method of employment.

The mortar section could also be employed in direct support of a specific unit of the company; e.g., a rifle platoon. The section leader established direct liaison with the supported rifle platoon commander and conducted fire missions as requested by him. The weapons platoon commander was responsible for the control of the section's actions to include positioning and displacement.

The mortar section, or an element thereof, could be attached to a rifle platoon. Attachment was justified when the mortar section could not give adequate support to a rifle platoon by operating in general support or direct support. Situations for attachment arise when a rifle platoon were: Operating as the advance party in an approach march; operating as a patrol whose route takes it out of mortar range; or conducting a withdrawal or is situated in a platoon strong point. When a mortar squad became attached to a rifle platoon, the rifle platoon commander assumed the tactical command, supply, and administrative functions normally exercised by the weapons platoon commander. Attachment was the least desirable method of employment. The employment of separate mortar squads attached to individual platoons lessens the destructive power achieved by consolidating the section. Attachment also increased the problems associated with ammunition distribution and resupply, as well as fire control.

In June 2011, the US Army's Program Executive Office for Ammunition fielded the Army's first improved M224A1 60mm LWCMS to 1st Special Forces Group in Fort Lewis, Washington. 1st Special Forces Group was the first US Army unit to receive the new mortar. Eventually all former legacy M224 systems in the US Army were to be replaced with the new lightweight systems. The US Army hoped to replace all existing M224 mortars with M224A1s by 2014. US Marine Corps also began receiving M224A1s by 2012.

The M224A1's new M225A1 cannon tube on the new system was made from "Inconel," a nickel-based material, as opposed to steel. Inconel was just as strong as steel, but was significantly lighter. It also had better wear characteristics and had the potential for a longer service life. Additional testing and evaluation was required before the service life could be extended passed the existing round limit. The new M170A1 bipod, which held the cannon steady at the desired elevation and angle, was also completely redesigned. Through changes such as incorporating the lighter, but still high performing materials of aluminum and titanium into the bipod, the bipod weight was reduced by 17 percent. In addition to a reduction in weight, the bipod’s new design requires less maintenance. One of the major upgrades included gears that did not need to be lubricated by grease and oil. The kevlar coating was reinforced with composites and protective coatings infused with lubricants that eliminated the need for external lubrication. The M225A1 cannon, M170A1, and M7A1 baseplate meant that the overall weight on the M224A1 was reduced by 20 percent over the earlier M224, a reduction of 9.3 pounds. This improvement represented the first major redesign of a 60mm mortar system since the 1970s.