I think that the action should be rolled by the gunnery officer directing fire. This should be a Rival with actual levels in Gunnery rather than Minions with group skills.
I used "each turret is a minion, each battery a group" with reconfigure on the fly as desired for available targets... but with the three new actions, those get even meaner. But note that Imperial Gunnery Corps adversary entry is a minion entry.