The M777A2 is an improved version of the standard M777 lightweight 155mm towed howitzer (referred to as LW155 in the U.S. Army) designed and manufactured by the Company BAE Systems. The M777A2 is a towed 155 mm Howitzer jointly developed by the U.S. Army and U.S. Marine Corps to replace the M198 155mm towed howitzer.
Country users: Australia, Canada, India, Ukraine, and the United States
Technical Data
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Gun
The M777A2 lightweight 155mmm towed howitzer uses a 155 mm/39 caliber ordnance using the same barrel as the US Army M109A6 self-propelled howitzer. It can be elevated to 71º and depressed to -3º. with traverse left and right of 23°. In July 2016, U.S. Marine has tested the M777A2 fitted with M776 Chrome Tubes which helps to extend the life of the tube by two to three times and prevented the buildup of residue within the bore during controlled testing. The elevating mass comprises two sub-assemblies, the cradle, and the cannon tube assembly. The cradle includes four extruded titanium tubes, an accumulator, two recoil cylinders,, and a balancing gear. The cannon tube assembly includes the cannon tube, muzzle brake, towing eye, primer feed mechanism,, and screw breech. The M777A2 system makes extensive use of hydraulics to operate the breech, loading tray,, and suspension system to reduce crew size and fatigue. Additionally, the M777A2 provides significant time savings for displacement and emplacement. Its primer feed mechanism supports a maximum firing rate of four rounds per minute and a sustained rate of two rounds per minute. In the firing position, two stabilizers are deployed at the front and two split trails fitted with self-digging spades and dampers at the rear. A small hydraulic hand pump is installed at each wheel station to raise and lower the system into and out of action. The M777A2 is operated by five military personnel to handle the various functions of the gun. It can be ready to fire in less than three minutes and can leave its firing position at the same time.
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Ammunition
The M777A2 lightweight 155mmm towed howitzer can fire the full range of U.S. 155mm ammunition including unassisted projectiles to a range of 24 km and assisted projectiles to 30 km. With the upgraded fire controls system, it can also fire Excalibur Precision 155 mm Projectiles, Global Positioning System (GPS)-guided, extended-range artillery projectile M982 and M982A1 at a maximum range of 40 km. The target, platform location and GPS-specific data are entered into the projectile’s mission computer through an Enhanced Portable Inductive Artillery Fuse Setter. Excalibur uses a jam-resistant internal GPS receiver to update the inertial navigation system, providing precision in-flight guidance and dramatically improving the accuracy of fewer than 2 meters of miss distance regardless of range. Excalibur has three fuse options (point-detonation, point-detonation-delay, and height-of-burst) and is employable in all weather conditions and terrain. Excalibur’s capability allows for first-round effects on targets while simultaneously minimizing the number of rounds required to engage targets and minimizing collateral damage.
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Mobility
The M777A2 barrel is mounted on a carriage which includes two main components, the body,, and the saddle. Mounted on either side of the body is a hydro-gas suspension unit fitted with a stub axle and one aluminum road wheel on each side. In the travel position, the M777A2 is towed by its muzzle by a military truck. which has a capacity of 2 tone minimum. In the US Army and Marine corps, the M777A2 is towed by the 7-ton Medium Tactical Vehicle Replacement (MTVR) truck.
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Combat Equipment
The M777A2 lightweight 155mmm towed howitzer has a Digital Fire Control System (DFCS) that includes an inertial navigation unit with Global Positioning System backup to allow it to self-locate. The DFCS also includes a mission computer, displays, and digital communications. Software upgrades incorporating the Enhanced Portable Inductive Artillery Fuse Setter and the Excalibur Platform Integration Kit hardware give the M777A2 the capability to program and fire the Excalibur precision-guided munition. The M777A2’s Digital Fire Control System (DFCS) is capable of determining onboard ballistic computations within 1 mil. The DFCS uses a global positioning system, an inertial navigation unit, and a vehicle motion sensor to accurately locate and orient the weapon thus improving precision and responsiveness. The system integrates radios for voice and digital communications as well as a chief of section display, which aids in navigation during movement when mounted in the cab of the prime mover. The system’s mission computer processes the fire mission and provides directional commands to the displays of the onboard gunner and section chief.
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