The hull was crowned by a flat-domed cast superstructure that superficially resembled a circular conventional turret. In reality however it was at first planned to be fixed; the 47 mm gun was supposed to traverse through a horizontal slit like in a pill-box, rotating on a pivot fixed to the hull floor, a proposal made by Colonel Balland. In a second version of this design by engineer Jean Restany, the "pseudo-turret" was traversable, but simply carried along by the electrically driven gun-mount; the turret therefore would not have to be equipped with a heavy gun-mantlet and, not bearing the weight of the armament, could be much lighter. On the right side of the superstructure a vertical cylinder protruded, on top of which a small rotating commander's cupola was fitted, that was armed with dual co-axial machine guns. The superstructure, with the commander/gunner on the right and the loader on the left, had sufficient room to hold a Schneider 47 mm antitank gun that was much more powerful than the shorter 47 mm SA 35 gun equipping the standard APX1 and APX4 turrets. Expecting that this superior firepower would give his design a clear advantage leading to a quick production contract, as had so often happened in the past, Renault was unpleasantly surprised when lobbying by Poniatowski contributed to a change in specifications to the effect that a 75 mm gun had to be carried in the hull. The ACK1 hull was simply too flat for this. To save his project Renault started a strong counter-lobby. Part of this was proposing, already on 10 December 1936, that as an alternative option the turret should hold a longer (at least L/29) main 75 mm armament. It was also claimed that the weight of the projects, 24 tonnes, could be reduced to 19.6 tonnes by limiting the armament to a single gun.