What a 6-inch coastal battery could deter

How effective would a 6-inch gun be in a coastal-defence battery?

It could drive off a cruiser armed with 6-inch guns and might also deter an 8-inch cruiser under favourable circumstances.

The battery is a useful deterrent against the opponents most likely to enter its range. A 6-inch cruiser would have to respect comparable fire coming from a fixed shore position. An 8-inch cruiser might also be forced away, although that outcome is less certain. The fort is best judged by the ships it can deny access, without expecting it to defeat capital ships.