The adoption of iron armor meant that the traditional naval armament of dozens of light cannon became useless , since their shot would bounce off an armored hull . To penetrate armor , increasingly heavy guns were mounted on ships ; nevertheless , the view that ramming was the only way to sink an ironclad became widespread . The increasing size and weight of guns also meant a movement away from the ships mounting many guns broadside , in the manner of a ship @-@ of @-@ the @-@ line , towards a handful of guns in turrets for all @-@ round fire .