As I made the artillery, I was thinking "what a shame I cant shoot artillery myself".
So I made artillery calls !  

It is simply a priority target spawned by a weapon shot. This target is attacked first by all turrets in range and so artillery shoots on it !

I went and tried to make a vfx to visualize the priority target and convey a sense of power with it. I'm pretty happy with it !

Next to do : Changing weapon !