Looks heavy
Personally, I always stand by even numbers- fours and eights for miniguns and similar sorts of shapes. Looks more balanced, and eight is dense enough to get that cool rolling effect when you animate them for spin, without getting everything all crowded. If you want a small number of barrels, I recommend twinning it and leaving it more of a two-sided design.
BTW: If those barrels with the vent-holes are modeled (not transparency-texed) can you email me a model of one of them? When I try to do vented cylinders with Booleans my software goes all funky, and gives me something harder to describe. I think it's what Lovecraft was going on about when he described horrific non-Euclidean shapes...