Depends on the scale. I mean, the models themselves are comparable to BFG size, but the scale of the ship seems to be a lot smaller, like I'd maybe rate the battleship as being maybe Star Wars scale or less (e.g. .6-1.2km for ship length). That'd make the turrets more reasonable, especially if they were a sort of linear acceleration guns, which they appear to be. If nothing else, you can always cut them short!