In order to update the existing fleet of 155 mm M109G self-propelled howitzers of the German Bundeswehr, Rheinmetall W & M GmbH has undertaken a programme to modify the vehicles to a new standard. The main modification is the replacement of the existing 155 mm barrel with a new 39 calibre barrel based on the ordnance of the FH-70 towed howitzer, but other modifications were introduced at the same time.

The installation of the new 39 calibre barrel allows the full family of improved 155 mm ammunition to be fired. This family includes High Explosive (HE), illuminating and smoke, all of which can be fired to a maximum range of 24,700 m. Enhanced range projectiles such as Base Bleed (BB) can be fired to a range of 30,000 m. Various carrier projectiles such as the Rheinmetall RB 63 and Rh 49 can also be fired.

The new ordnance is mounted in the cradle and recoil system of the M109G and has a revised obturation system. An external rotation key is located in a cradle extension under the barrel and the barrel dust cover of the original M109G has been modified.

Other innovations to the barrel include a new flexible bellows and a fume extractor located halfway along the tube.

The original M109G muzzle brake is retained but is held in place by new fasteners. Other modifications to the ordnance involve machining alterations to the breech ring and buffer.

Modifications to the turret include a new projectile magazine at the rear of the turret bustle. This can be reloaded through two outward-opening doors and holds 22 projectiles. The vehicle can carry a total of 34 projectiles. New provisions are made for propellant charge stowage. Other changes include door locks, a blast cover for the panoramic sight, and new sealing for the shields. A hand-drive mechanism is provided forthe traversing gear and new elevation balancing cylinders are provided.

Changes to the rest of the vehicle include a new barrel clamp, revised ventilators, a new air filter system, a new instrument layout for the driver, the location of a driver's control panel in the main compartment, a turbo-supercharger system, reinforced torsion bars on the suspension and a driver's hatch lock. Alterations have been made to the engine power pack to allow it to be replaced more readily.

Other modifications are that the turret hydraulics have been altered to suit the metric system and the traversing gear hydraulic motor is now the same as that used on the Leopard 1 MBT. An electrical firing circuit has been introduced and various new fire-control data panels have been incorporated.

The German 155 mm M109A3G self-propelled artillery systems are also being fitted with the KUKA Ammunition Handling Kit, details of this are given in the earlier Automatic loaders and flick rammers section.

The first production contract is for a total of 262 systems for delivery from July 1999 through to June 2000. There is also an option on another batch of 262 AHKs.

Modification programme complete for the German Army. The overhaul and conversion work was carried out by a German Army depot.