The GCT is a self-propelled 155mm howitzer of French origin. Giat started the development in 1969 when the French government announced the AXM 105 and Mk.F3 were to be replaced. GCT stands for Grand Cadance de Tir, French for high rate of fire. This name was chosen while it had a rate of fire which was twice of what was normal at the time. The first prototypes were built in 1972 and the vehicle entered production in 1977.

The GCT is based upon the chassis of the French AMX-30 main battle tank. The turret is fitted in the middle and the drive train in the rear. Unlike many self-propelled howitzers the fighting compartment does not extend into the rear hull but is fully separate. A unique feature is The whole rear of the turret can be opened to allow the racks of six shells and the charges to be loaded quickly.

The GCT is armed with a 40-calibre 155mm howitzer that is connected to an automatic loader. It is possible to fire a burst of six rounds in 45 seconds. The normal rate of fire is 4 to 6 rounds per minute and during sustained fire 1 to 2 rounds are fired every minute. The maximum range with standard French HE ammunition is 23 km, with US M107 rounds it is 18 km and HE base bleed rounds have a range of 29 km. A machine gun is fitted on the turret roof for self defense.

The GCT is operated under full armor protection. The steel armor gives protection against small arms fire and shell splinters. NBC and fire suppression systems are fitted. A total of 4 smoke dischargers are fitted.

The GCT is based on the tracked chassis of the AMX-30 tank and has a good off road performance. A Hispano-Suiza 720hp diesel engine provides propulsion and an auxiliary power unit provides power when the engine is not running.

The main user of the GCT was the French army. It was exported to three other nations. In French service the GCT is called the AUF-1. Given its age it is either to be upgraded or no longer in active service.