2S1 122 mm self-propelled howitzer is a light armoured unit of artillery of circular shooting based on high-speed crawler undercarriage. The all welded steel hull comprises three compartments: driver\'s at the front-left, engine behind the driver and the turret at the rear. The crew includes 4 men and additional 2 in ammunition carrier vehicle. The main armament is designated 2A31 and is a modified version of D-30 towed howitzer. This has a semi-automatic vertical sliding wedge breech block and a firing pin that can be recocked in the event of misfire.