Royal Ordnance Nottingham has developed a range of 155 mm ordnance systems that can be installed in new self-propelled artillery systems or retrofitted to existing vehicle platforms.

The 39 calibre 155 mm ordnance is, for example, fitted to production versions of the Marconi Marine, Land and Naval Systems, AS90 self-propelled artillery system ordered by the British Army in 1989, while the 47 and 52 calibre ordnances have been installed in the AS90 for trials and development work.

The Royal Ordnance 155 mm 39 and 155 mm 52 calibre weapons are also installed in the Marconi Marine, Land and Naval Systems AS90 Universal Turret - covered in the previous entry - which remains at the prototype stage.

The M109 system has also been fitted with Royal Ordnance 155 mm 39, 47 and 52 calibre ordnances for trials and development work.

All these 155 mm systems have chambers conforming to Quadrilateral Ballisitics Memorandum of Understanding (MoU) and can fire all 155 mm ammunition conforming to this MoU.

They all have rapid breech operation based on the sliding block principle with Crossley pad obturation. The flick rammer is hydraulically powered and electronically controlled. Firing mechanism is electric/ percussion with a 13 mm vent tube or DM191/M82. Tube loading is manually assisted.

A burst rate of fire of three rounds in 10 seconds can be achieved with an intense rate of fire of 6 rds/min for a period of 3 minutes. Breech operation is automatic following loading of first projectile and charge.

The following reversionary modes are available:

(1) manual tube loading - manual insertion

(2) power rammer - manual rammer

(3) firing mechanism - lanyard firing.

Optional enhancements include automatic primer tube loading, barrel temperature indicator and fallback detection.

Using a Base Bleed (BB) round a range of 40 km can be achieved with the 52 calibre ordnance.

The 39 calibre ordnance is in production for the AS90 and in service with the British Army. The 155 mm 52 calibre ordnance has been trialled on AS90 and will be fitted to part of the British Army's fleet of 155 mm AS90s as part of an upgrade. Prime contractor for this upgrade, which also includes the South African Somchem Division of Denel Modular Charge System, is Marconi Marine, Land and Naval Systems.