Switching ammo types in battle?

[LordBravey]

Is there a way? I have a gun that uses bullets, and a cannon. So I have bullets and cannon ammo. However, both guns are using bullets, and when I run out, switch to cannon ammo. Is there a way to manually switch between these two? Also, is this a bug?

And a side question, if this isn't a fantasy mod, why are there golems and ghosts and skeletons and the like? I'm not complaining, I'm just curious.