M777 155mm Ultralightweight Field Howitzer


The 155 mm Lightweight Howitzer was originally developed as a private venture. Its origins can be traced back to the early 1980s when Vickers Shipbuilding and Engineering Limited (VSEL) (which today is BAE Systems Land Systems) originally perceived a potential market for a lightweight 155 mm towed howitzer.

In the spring of 1987 the project definition was completed. Its objective was to have a weapon with the same range as the US Army’s M198 155 mm towed howitzer but weighing no more than 4,000 kg.

The current M198 weighs 7,163 kg which limits its air mobility; it can only be carried by two helicopters, the US Army Boeing CH-47 or the US Marine Corps Sikorsky CH-53.

The US Army was fully briefed on the system and agreed that if the company built a prototype of the system with its own money it would carry out a complete evaluation of the system.

In September 1987, the main board gave approval to build two prototypes of the system, which is today called the 155 mm Lightweight Howitzer. Both were completed in late 1989.

The complete upper part of the weapon was test fired at Eskmeals in June 1989 with a total of 50 rounds being fired at all elevations, 12 of which were zone 8S (top charge).

Although the weapon was originally targeted at the US Army, the US Marine Corps took the initiative as it was looking for a lightweight 155 mm system to replace all current 105 mm and 155 mm towed artillery systems.

Following its unveiling at the 1989 Association of the United States Army Exhibition in Washington DC, one of the two prototypes went to the US for early evaluation.

This evaluation, under the supervision of the US Army Armament Research and Development Command on behalf of the US Marine Corps, took place in three phases through to 1990.

It also completed limited land mobility trials and airlift certification in single and split mode. At the end of Phase 1 the system was awarded limited live crew clearance for the US.

Phase 2 was conducted at the US Marine Corps Base at Camp Lejeune, North Carolina and at the Naval Base at Little Creek, Virginia. During Phase 2 the system achieved a single lift with the UH-60L Black Hawk helicopter. Amphibious trials were carried out successfully at Little Creek.

The final phase took place at Aberdeen Proving Ground, Maryland where the system carried out successful climatic chamber firings at temperatures ranging from -25 to +145°C. These climatic firings were followed by air transportability (split lift) trials and 622 km of land mobility trials on test tracks ranging from trails to Belgian blocks and included wading to a depth of 1.5 m.

The US then had a competition which involved extensive tests with the 155 mm Lightweight Howitzer and the Light Towed Howitzer developed at the then Royal Ordnance facility at Nottingham. In the end the former was selected.

For the US programme, Textron Marine & Land Systems was selected to be the prime contractor with the then Vickers Shipbuilding and Engineering Limited being the main sub-contractor.

By 1998 it was clear that the US programme was running into problems and early in 1999 the now BAE Systems Land Systems assumed the role of prime contractor of the troubled XM777 towed artillery system from its team member Textron Marine & Land Systems. This company no longer has any involvement with the programme.

In September 2000, following an extensive competition, BAE Systems Land Systems finally selected its core industrial supplier base for US production of the XM777 155 mm weapon.

The body assembly is manufactured by HydroMill Inc of Chatsworth, California, stabilisers, spades and trails are supplied by Major Tool and Machining Inc of Indianapolis, Indiana, the breech operating load tray system is provided by Rock Island Arsenal, Rock Island, Illinois, with titanium being supplied by RTI International Metals Inc of Niles, Ohio.

In late 2002, BAE Systems Land Systems was awarded a USD135 million contract by the US DoD for the Low Rate Initial Production (LRIP) of the M777 following its type classification.

Under the initial phase of the LRIP contract, BAE Systems Land Systems has built 94 M777s for the US Marine Corps, with first weapons delivered in February 2003 from the company’s Hattiesburg, Mississippi facility.

The M777, which while under development was called the XM777, will replace the current 155 mm M198 towed howitzer which weighs 7,163 kg.

Under the five-year Engineering and Manufacturing Development (EMD) contract a total of nine systems were built at the BAE Systems Land Systems facility at Barrow-in-Furness. These have underwent an extensive series of tests in the US during which more than 10,000 rounds of ammunition have been fired.

The nine EMD guns were followed by two preproduction (PP1 and PP2) guns from the US production line to test and validate the US production base.

According to BAE Systems Land Systems, about 70 per cent of the M777 is made in the US, including the 155 mm/39 calibre barrel, which is provided by Watervliet Arsenal. Barrow-in-Furness manufacture the upper cradle as well as the suspension and running gear.

In March 2005, BAE Systems Land Systems was awarded a contract worth USD834 million covering the supply of 495 M777A1 155 mm/39 calibre lightweight howitzers for the US Army and Marine Corps.

The 495 M777A1 will be delivered over a four-year period starting in July 2006 and running through to October 2009.

The US Army is expected to take delivery of 233 systems and the US Marine Corps 262, as the replacement for the current in-service and much heavier 155 mm M198 towed howitzer.


Although the M777 uses advanced materials in its construction, it is claimed to be simple to operate and maintain under field conditions.

Marines with Golf Battery, 2nd Battalion, 11th Marine Regiment, 1st Marine Division, conduct a mock firing drill with an M777 Howitzer during Weapons and Tactics Instructor Course 1-14 near Yuma, Ariz., Oct. 5, 2013. A Helicopter Support Team with Landing Support Company, Combat Logistics Regiment 17, 1st Marine Logistics Group, rigged the artillery pieces to a CH-53E Super Stallion in order for them to be transported to the training site.

The 155 mm/39 calibre ordnance (M776E2) is essentially that of the M284 barrel used by the US Army’s M109A6 Paladin fitted with the M199 muzzle brake as used by the current towed M198 howitzer but modified to take a towing eye. The conventional screw breech is hydraulically operated and opens vertically. For this application the breech of the 155 mm M776E2 cannon has the screw breech turned 90° to allow vertical operation between the cradle tubes. Source army-guide.com

M777 howitzer A1 and A2 variants

The M777 will be the artillery system for the Stryker Brigade Combat Teams (SBCT). The M777 is normally operated by a crew of eight men but can be operated with a reduced detachment of five.


The systems fitted with the digital fire control system are designated M777A1, and those with the software update which allows the firing of the Excalibur projectile, M777A2. M777A2 received full material release in July 2007, clearing the upgrade for fielding. All M777A1 systems will be upgraded to the A2 standard.


The M777 was deployed by the US Army and Marine Corps to Afghanistan in December 2007 and to Iraq in 2008.

The Excalibur projectile was first deployed in Afghanistan in March 2008.

Excalibur projectile

XM982 Excalibur Shell

Excalibur is the world’s first GPS driven projectile.

Engineers had to make delicate circuitry inside an artillery round. That’s like dropping a computer from the top of a skyscraper and expecting it to work! But that’s not the only thing that makes Excalibur the present and future choice for artillery.

Excalibur is a 155mm artillery round that can strike within 10 meters of its intended target. It has a 40 kilometer range that has a high angle of attack. Why is that important? Well, in combat, enemy combatants can hide near infrastructure that makes them hard to eliminate. That’s because typical artillery’s angle of attack is somewhere around 45 to 50 degrees. Excalibur’s angle of attack is somewhere around 80-85 degrees. That makes hiding nearly impossible.

And Excalibur virtually eliminates one of the most dangerous aspects of modern combat – friendly fire. In tests, Excalibur was fired with a 15 degree misfire. Now, over big distances, that is a huge mistake! Well, Excalibur’s GPS system and Canard Control Guidance took over and reguided the round back to within 2 yards of its intended target! That’s impressive. Source gopaultech.com


By August 2008, over 400 systems had been delivered to the US Army and USMC.

The Indian Ministry of Defence (MoD) has requested for 145 M777s from multiple contractors under a foreign military sales (FMS) contract.

The $885m contract will also include procurement of associated equipments and logistical support services for the aircraft.

The MoD, however, failed to sign off a deal by the 15 October 2013 deadline imposed by BAE, causing the company to initiate shut down of its M777 howitzers production line at Burrow-in-Furness, UK.

M777 armament

The M777 matches the firepower of current generation 155mm towed systems at less than half the weight. The Howitzer is equipped with a 39-calibre barrel. The muzzle velocity (at Charge 8 super) is 827m/s.

The maximum firing range is 24.7km with unassisted rounds and 30km with rocket-assisted rounds. The M777A2 will fire the Raytheon / Bofors XM982 Excalibur GPS / Inertial Navigation-guided extended-range 155mm projectiles using the Modular Artillery Charge Systems (MACS). Excalibur has a maximum range of 40km and accuracy of 10m.


First firing trials of the M777A1 with Excalibur took place in August 2003. First production rounds were delivered in September 2006. Excalibur successfully completed limited user test in March 2007. It was first fielded in Iraq in May 2007 and in Afghanistan in February 2008.

The M777 is able to deliver up to five rounds a minute under intense firing conditions and is able to provide a sustained rate of fire of two rounds a minute.

Precision Guidance Kit-Modernization (PGK-M)

The PGK-M builds on mature, battle-proven technology to improve the accuracy of 155mm projectiles. It will increase maneuverability and incorporate anti-jam capability – requirements for today’s evolving battle space.

Proven technology

-Completed over 200 tests demonstrating a TRL 7
-<10m circular error probable (CEP) accuracy
-High angle of attack

Innovative guidance

The kit combines enhanced Global Positions System (GPS)-based navigation with an innovative, roll-stabilized guidance unit and antenna array. This integrated technology, paired with a proven, variable deflection canard control method, allows for advanced in-flight correction capabilities.

The PGK-M technology is designed to help warfighters complete every mission accurately:

-Precision at longer distances keeps soldiers away from threats
-Improved GPS anti-jam performance
-Enabled technology compatible for GPS restricted environments (semi-active laser, imagers, pseudolites, datalink, etc.)

Reduced dispersion

Our kit dramatically reduces the dispersion associated with 155mm unguided artillery rounds, achieving precision target engagement. Projectiles fitted with PGK-M provide artillery teams on the battlefield with accurate fire support capabilities that friendly forces can rely on in urban areas.

-Improved accuracy against modern threats
-Reduced Circular Error of Probability (CEP)
-Decreased collateral damage

Low cost

The PGK-M’s highly accurate, lethal capability enables one-shot hits on the target. It requires less ammunition than conventional artillery to complete the mission, saving on costs, and increasing effectiveness.

Source baesystems.com

Fire control

fire-control (1).png

The M777A1/A2 is fitted with the SELEX Sensors and Airborne Systems UK Ltd LINAPS (Laser Inertial Artillery Pointing System) artillery pointing suite coupled to a Lincad Ltd made battery and muzzle velocity radar. Source poadu.wordpress.com

The LRIP systems employ an optical sighting system for direct and indirect firing by day or night. Full production systems will be fitted with the General Dynamics Armament Systems Towed Artillery Digitisation (TAD) system. LRIP systems will be retrofitted with TAD.


The TAD digital fire control system provides onboard ballistic computation, navigation, pointing and self-location, providing greater accuracy and faster reaction times.

The TAD system also includes a laser ignition system, electric drives for the howitzer’s traverse and elevation and a powered projectile rammer. Source army-technology.com



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