You mean a flail?
They don't keep a giant rock man stuffed inside. Neither golems nor barriers are actually ejected from the cylinder. Insofar as I can tell, their molecular makeup is stored in the crystal and, when fired, it simply converts the surroundings to suit those needs. Barriers form and rise up from the dirt, etc.
As for Heat Buster-- flame is insubstantial, and will expand in the nearest open direction to follow it's air supply of it's own accord. Steam, like wind, would need to be built up in the chamber, then focused and released. At best, I could see a gun-like skill arising that has a significant durability penalty on the cylinder. -3 dura per shot kinda thing.
It would likely also be slow to load, although may do a linear "AoE" to pierce targets directly en route to the actual target.
-Drools- Do want.
I could almost see this being used just to destabilize and then launch crystals so they explode on impact. Water cannon at mach 3, yes please.
I was thinking more of a Shock Variable type of cylinder that makes Shock into a Railgun or somthing instead of flashy lighting.