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Lightweight 155 mm Howitzer

The Lightweight 155 mm Howitzer (LW155) is a highly successful joint U.S. Army/Marine Corps acquisition program that entered full-rate production in 2005. The prime contractor for the LW155, which is designated the M777, is the U.K.’s BAE Systems. It has delivered more than 600 of the towed howitzers to the Army and Marine Corps. The M777 will become the Corps’ sole howitzer.

The proven combat performance in Iraq and Afghanistan of the M777, or “Triple 7,” has earned it the reputation of being the most effective towed howitzer of its kind.

The goal of the LW155 program was to develop a more capable replacement for the aging and heavy M198 155 mm towed howitzer in both the Marine Corps and Army, one that weighed less than 10,000 pounds. That goal was achieved.

M777 155 Howitzer

Marines from Kilo Battery, 3rd Battalion, 11th Marine Regiment, 1st Marine Division, send a round down range with their M777 155 mm howitzer during artillery relocation training in the Yausubetsu Maneuver Area, Hokkaido, Japan.

The weight of the M777 is 9,700 pounds, compared with more than 16,000 pounds for the M198. This was made possible by the use of titanium and aluminum alloys in all of its major structures except its steel gun tube, as well as hydraulic systems to operate several components.

This weight reduction translates into greater strategic deployability – two M777s can fit into a C-130 transport, compared with one M198 – and greater tactical mobility. Unlike the M198, the M777 is light enough that it can be airlifted by all Marine Corps medium- and heavy-lift helicopters (CH-53Es, CH-46Es, and CH-53Ds) as well as new MV-22 Osprey tilt-rotor aircraft, providing commanders with significant operational flexibility.

Christopher Hatch, the LW155 deputy program manager, noted, “An extremely valuable feature of the M777 has been its ability to be moved rapidly by rotary-wing aircraft to different locations that are inaccessible to ground transportation. It’s uniquely suited for Afghanistan, where it’s been light enough to be lifted into high-altitude forward operating base locations. We can’t lift an M198 into those places.”

The M777 features greater survivability than the M198 by virtue of its shorter emplacement and displacement times – both under three minutes compared with 10-12 minutes for the M198 – providing it the ability to “shoot and scoot.”

The LW155 fires standard unguided projectiles to a range of 15 miles and rocket-assisted projectiles to 19 miles. Its rate of fire is four rounds per minute maximum and two rounds per minute sustained.

The latest M777A2 version of the howitzer added a software upgrade and a Digital Fire Control System (DFCS) from BAE Systems that allows the gun to program and fire a longer-range and more accurate round – the M982 Excalibur Guided Projectile. The Excalibur munition, developed by Raytheon and BAE Systems, can reach ranges in excess of 25 miles while always landing within 10 meters of its target.

This gives the Marine Corps’ and the Army’s towed artillery the ability to deliver precision fires, allowing them, according to BAE Systems, “to target a specific room within a building, reducing the chance of innocent casualties and allowing supporting fire to be brought down much closer to friendly troops.” U.S. forces have used the Excalibur projectile effectively in Iraq.

The M777A2’s onboard DFCS is used to accurately locate and aim the gun. With the majority of its components mounted on and underneath the gun’s main cradle section, the DFCS includes a GPS receiver; an inertial navigation unit; a vehicle motion sensor; a mission computer; a battery power supply; secure voice and data radios for communicating with and passing data to and from the fire direction center; and separate displays for the gunner, assistant gunner, and chief of section.

The hand-held Chief of Section Display is connected to the DFCS by a cable and shows the details of a fire mission transmitted from the fire direction center – the firing azimuth, elevation, and propellant charge – on its screen.

Hatch noted that the DFCS has made the LW155 guns more autonomous. “We’re finding that, at many of the forward operating bases in Afghanistan, only two guns are being deployed instead of an entire battery of six. Commanders are actually getting greater coverage by dispersing the guns more geographically,” he said.

M777A1 Howitzer

An M777A1 howitzer lights up the gun line as Bravo Battery 1/11 conducts a fire mission. Bravo Battery was then the only unit utilizing the M777 in combat.

The M777 achieved an initial operational capability in December 2005. All USMC guns are now M777A2s and Excalibur-capable. The Marine Corps has fully fielded the LW155 to its 10th, 11th, 12th, and 14th Marine Regiments and to its schoolhouses. Additional guns are outfitting the Maritime Prepositioning Ships and war reserve stocks.

The Marine Corps’ Approved Acquisition Objective is 511 M777A2s (its original plan was to buy 356). The service had ordered 489 as of this past July, with 372 delivered. The Corps is slated to receive its final deliveries in November 2012.

The prime mover towing the Marine Corps’ M777A2s is the 7-ton Medium Tactical Vehicle Replacement (MTVR) truck.

The M777A2 is exceeding its reliability requirement of 800 mean rounds fired between system aborts – achieving 880, Hatch said. Ironically, the biggest reliability issue to date, he noted, has been the wear and tear incurred by the cables that run to the gun, such as from the Chief of Section Display, and are out in the open.

An under way LW155 software upgrade effort aims to allow all of the ballistic computations to be done on the howitzer itself rather than relying on a fire direction center to transmit firing data to the gun. A forward observer would call in a grid location that would come directly to the gun instead of to the fire direction center, reducing the time to fire.

Another M777A2 upgrade in the works designed to reduce logistics costs involves removing the DFCS mission computer from the gun and embedding its functionality into the Chief of Section Display.

Canada acquired 12 M777s for its forces deploying to Afghanistan in February 2006 through U.S. Foreign Military Sales (FMS). It has ordered 25 more. Australia is buying M777s through FMS. The first of 35 weapons was delivered in August 2010. The U.S. government also has been discussing with India an FMS sale of M777s.

The M777 program is managed by the Army/Marine Corps Lightweight 155 mm Joint Program Office at Picatinny Arsenal, N.J. BAE System’s facility at Hattiesburg, Miss., is responsible for final integration and test of the weapon system. The manufacture and assembly of the complex titanium structures and associated recoil components are carried out at Barrow-in-Furness in the U.K.

This article was first published in Marine Corps Outlook: 2010-2011 Edition.


Glenn Goodman, senior editor of the Journal of Electronic Defense, is also a frequent contributor...