The 155 mm GCT turret was originally developed for use with the Giat Industries 155 mm self-propelled gun (known bythe French Army as the CN 155 AU F1-T)that was subsequently sold to the French, Iraqi, Kuwaiti and Saudi Arabian armies. In 1992, the turret was displayed on a Russian Federation and Associated States (CIS) T-72 MBT chassis.

The GCT turret was one of the four 155 mm turret systems evaluated in India installed on a T-72 MBT chassis.

The GCT turret is all-welded steel with the commander and gunner seated on the right and the loader on the left. The commander's cupola is equipped with periscopes for all-round observation and has a single-piece hatch cover that opens to the rear. The loader, who also operates the anti-aircraft machine gun, has a single-piece rear-opening hatch cover. The crew enters the turret via a door in each side.

The 155 mm 40 calibre barrel has a vertical sliding wedge breech block and is hermetically sealed by a metal blanking plate. The breech is hydraulically opened with manual controls for emergency use. The barrel has a double-baffle muzzle brake. The 155 mm gun has an elevation of +66°, depression of -4° and the turret can be traversed through 360°. Turret traverse and gun elevation are hydraulic with manual controls for emergency use.

Forty-two projectiles and cartridge cases are carried inthe turret rear arranged in seven racks of six identical projectiles and seven racks of six cartridge cases; a further 22 propelling charges for short range are housed near and under the loaders seat. Any combination of High Explosive (HE), illuminating or smoke projectiles are possible in racks of six similar projectiles, for example 36 (6 x 6) HE and six (1 x 6) smoke or 30 (5 x 6) HE, six (1 x 6) illumination and six (1x6) smoke. The various types of projectiles can be selected and fired with the automatic loading system without any prior preparation of the system. The gunner can select single shots or bursts of six rounds.

Turret reloading is via two large doors in the turret rear which fold down into the horizontal to provide a platform for the crew. The turret can be completely resupplied by a crew of four in 15 minutes or by a crew of two in 20 minutes. The gun can continue to fire while being resupplied.

The standard fire-control system consists of the following subassemblies:

(a) gimbal suspension providing for the mounting of the goniometer in the turret and permitting it to move freely by 10° relative to the axis in all directions

(b) one hermetically sealed conventional optical goniometer. Traverse angles are read on engraved drums and elevation angles appear on an elevation scale (c) one azimuth plate that can be manually adjusted and is provided with a spirit level to set the goniometer vertically

(d) a contrarotation device making it possible to preserve the vertical position of the goniometer during turret rotation

(e) a direct fire sight for anti-tank use.

The standard fire-control system in French Army 155 mm GCT service is being modernised by fitting an Inertial Fire Control (CTI) system which comprises the following components:

(a) platform unit (UPF)

(b) control and display unit (UCV)

(c) computer and control unit (UCC)

(d) inductive path measuring device (MPU). Basically this allows the GCT to know the exact coordinates of its position when it comes to a halt and the bearing of its ordnance, without the need to use any external optics.

A 7.62 mm or a 12.7 mm calibre machine gun can be mounted at the loader's station for anti-aircraft defence. The 7.62 mm machine gun has elevation/ depression limits of +45 to -10° and is provided with 2,050 rounds, of which 550 are for ready use. The 12.7 mm machine gun has elevation/depression limits of +50 to -20° and is provided with 800 rounds, of which 100 are for ready use. Two pairs of electrically operated smoke grenade dischargers are mounted on the toward part of the turret, below the main armament.

Sometime in 1999, Giat Industries expect to be awarded a combined development and production contract from the Delegation General pour I'Armement (DGA) to upgrade at least part of the French Army's fleet of 155 mm GCT (or AUF1) self-propelled artillery systems to extend their operational lives into the 21st century.

The substantial upgrade to the GCT will include the installation of a new 155 mm 52 calibre ordnance fitted with a new screw type breech mechanism, double baffle muzzle brake and a modified recoil system. A new modular charge system is being developed by Giat Industries and firing an extended range full bore - base bleed projectile a maximum range of 40 km will be achieved.

The turret will be stripped down and refurbished and it is expected that an automatic gun laying system will also befitted.

The chassis will also be refurbished and the current powerpack consisting of a Hispano Suiza HS 110 12-cylinder engine coupled to a mechanical

transmission will be replaced by a new powerpack consisting of a Renault Mack E9 series diesel coupled to a new ENC 200 transmission. The suspension will also be upgraded for improved cross-country mobility.

According to Giat Industries, some 80 per cent of the maintenance requirement for the French Army GCT is in the chassis.

The exact number of systems to be upgraded has yet to be decided but the first batch will consist of 70 units with the second batch expected to consist of 104 units. When upgraded they will be designated the AUF2.

Production complete but can be resumed. In service with France (273 systems), Iraq (86), Kuwait (18) and Saudi Arabia (63).