Either way, now the idea was to install the French 155mm Canon de 155 Grande Puissance Filloux (GPF) mle.1917 high-power howitzer on the F1 chassis. This gun would fit perfectly into the huge assault tank. As FCM already had enough experience with “risking” building something before the army orders came thru, it decided to tried its luck one more time and to start building 4 of these turretless tanks. During the construction process, the rear part of the vehicle housed now a superstructure, made of 60mm plates. Inside this superstructure there was the modified 155mm GPF gun plus the ammunition. The access to the superstructure was allowed via a passage in the rear part of the vehicle. The frontal turret was also not installed, there was just a miniturret with two 7,5mm machineguns on the roof of the superstructure, that could – if necessery – fire also at airborne targets.
最终决定1917型 155mm GPF 大威力榴弹炮将被装上F1的底盘。这门炮可以轻松装上这辆巨型突击坦克上。FCM对于“冒险行为”已经非常有经验了,于是他们决定再冒险一次,制造四辆这种突击炮。在建造过程中,车体的后半部分装了一个战斗室,装甲厚度60mm。在战斗室内部还装有155mm GPF火炮以及其所使用的炮弹。车体的后方有一个门,可以从那个门进入车辆的后部。原来前部的炮塔被取消掉了,取而代之的是一个装在战斗室顶部的小炮塔,上面装有两挺7.5mm机枪,在必要的时候可以起到防空的作用。

