The armament of the "Defence"-class ships was intended to be 18 smoothbore, muzzle-loading 68-pounder guns, eight on each side on the main deck and one each fore and aft as chase guns on the upper deck, plus four rifled breech-loading 40-pounder guns as . This was modified during construction to eight rifled 110-pounder breech-loading guns, ten 68-pounders and four breech-loading guns. Both breech-loading guns were new designs from Armstrong and much was hoped of them. Six of the 110-pounder guns were installed on the main deck amidships and the other two became chase guns; all of the 68-pounder guns were mounted on the main deck. Firing tests carried out in September 1861 against an armoured target, however, proved that the 110-pounder was inferior to the 68-pounder smoothbore gun in armour penetration and repeated incidents of breech explosions during the Battles for Shimonoseki and the Bombardment of Kagoshima in 1863–1864 caused the navy to begin to withdraw the gun from service shortly afterwards.