User blog comment:FairyRaven/Fairy Tail Chapter 391: Gray vs. Silver, Review and Commentary/@comment-4933386-20140705051946/@comment-7418318-20140706081641

He landed that piece of rubble, though it didn't do much.

And I doubt Gray could create ice that can act all on its own. I doubt you can pre-program movments into the ice or give it some kind of conciousness. Besides that Gray specialized in static Ice-Make, so if there's anyone who would do such an elaborate and dynamic cannon it'd probably be Lyon.