User blog comment:Ficus7/Allowed Technology/@comment-24171828-20140913160116/@comment-14850713-20140914172840

Ej, ERA was made to defeat HEAT rounds. Armor-piercing (AP) shells of battleship guns are like sabot rounds of tank guns. Their hardened warheads pierce through armor by sheer velocity. So even if you scale up ERA to ship size, they will still be useless against AP rounds capable of punching through the main armor.