Bombardment of Kagoshima
The intended armament of "Achilles" changed no less than five times before it was finally mounted. She received four rifled 110-pounder breech-loading guns mounted on the upper deck, two of which served as chase guns at the bow and stern, and 16 smoothbore, muzzle-loading 100-pounder Somerset cannon, eight on each side on the main deck. The breech-loading guns were a new design from Armstrong and much was hoped for them. 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 withdraw the gun from service shortly afterwards. In 1865, six 68-pounder smoothbores were added, three on each side of the main deck, although she was not comprehensively rearmed until her 1868 refit.