[GLITTERTECH] Cluster Mortar Does Not Fire

[tymur999]

I've had a few cluster mortars in my base for a while now. I've kept them in an unroofed area, and even when they lock on, they don't see to fire. Am I doing something wrong? I only kept the opening 2x2 so only the mortar fits. Is there some  kind of ammo I need? Please help me.