Gatling Gun for Transformers Prime Beast Hunters Voyager Class Optimus Prime. I add a version that can be printed piece by piece (they need to be glued), including a rotating barrel and  another one as a single piece.

As the title says, it's meant for the Voyager Class BH Prime (and it can be stored on its back). I don't own other scales of the figure, but you could try to fit it if you want, just consider that the peg for the hand's grip is 5 mm in diameter for this scale.