the French and Germans definitely decided to adopt their two separate tanks. The prototypes of the AMX-30 weighed , and were compact, with a width of , comparable only to the Swiss Panzer 61, and a height of , comparable only to the Soviet T-55. In contrast to the AMX-50, the AMX-30 was issued a conventional turret, because it was found that it was more difficult to seal oscillating turrets from radioactive dust and against water when the tank was submerged. Oscillating turrets also had a large ballistic weakness in the area of the skirt and turret ring. Originally, the first two prototypes were powered by a spark ignition engine, named the SOFAM 12 GSds. Later, a multi-fuel diesel engine was adopted, developed by Hispano-Suiza. The seven 1963 prototypes of the AMX-30 were later rebuilt with the new diesel engine. Two further prototypes, meant to be direct preproduction vehicles, were delivered in November 1965. Besides the diesel engines, they had changed hull and turret casts and different gun mantlets; the latter would again be changed in the production vehicles. The first production versions of the AMX-30, named AMX 30B to distinguish them from the AMX 30A prototypes, were completed in June 1966, manufactured with a welded and cast hull and a fully cast turret. The production version of the tank had a combat weight of . The AMX-30's survivability was based on its mobility; French engineers believed that the tank's mobility would have been compromised had they added enough steel plating to protect against modern anti-tank threats, including high-explosive anti-tank (HEAT) warheads. As a result, the type had the thinnest armour of any main battle tank produced at the time. The turret has a maximum armour thickness of , the armour sloped at 70 degrees on the front plate and 23 degrees on the side, offering protection against armour piercing projectiles. The Line-of-Sight armour values are: for the front of the hull; for the forward sides of the hull; for the rear sides and rear of the hull; for the hull top and bottom; for the turret front; for the turret sides; for the turret rear and for the turret top. Further protection is offered by a nuclear, biological and chemical protection suit, including a ventilation system. One of the unique features of the AMX-30 was the Obus à Charge Creuse de 105 mm Modèle F1 (Obus G) HEAT projectile