search subs or ss and you will find a bunch of answers.

Sometimes you can surface for air, pop smoke, and use the gun to take pot shots at ships

BUT:

1. The accuracy isn't real good at range (works good if your close)
2. The gunner you need to use is high level (and adds a lot of weight)
3. You could put a repairman on the slot and increase your repair

Or

1. You could leave the slot open to save wieght and add some buldge or increase speed (increase speed is my favorite).

• So it really is a nice thing, but not real effective in terms of practicallity.

the KM ss flak is tons of fun to use its guns .