armour at the muzzle. The 16-calibre gun weighed and fired a shell. It was credited with the nominal ability to penetrate armour. When the ship was refitted in 1881–85, she became the only British ironclad to have her entire muzzle-loading armament replaced by breech-loaders. Bellerophon received ten BL Mk III guns, mounted in the central battery and four 6-inch (152 mm) guns as chase guns fore and aft. The forward guns were mounted in new embrasures in the forecastle on the upper deck as the original guns were too low and were usually washed out in a head sea. Eight 4-inch breech-loading guns as well as four quick-firing 6-pounder Hotchkiss and 12 machine guns were fitted for defence against torpedo boats. The ship also received two Whitehead torpedo launchers that were carried on the main deck, outside the armoured battery. The new eight-inch guns were some longer than the original nine-inch guns and the central battery proved to be too small for effective use of the guns. ArmourBellerophon had a complete waterline belt of wrought iron that was thick amidships and tapered to thick at the bow and stern. From the height of the main deck, it reached below the waterline. The central battery were protected by a section of 6-inch armour, long, with transverse bulkheads at each end. The forward chase guns were protected by a strake of armour. The upper deck was thick over the battery and the main deck was thick. The armour was backed by of teak and the skin of the ship was thick. The total weight of her armour was . Construction For the first time since the construction of , the basic method of construction of an ironclad's hull was altered. The usage of longitudinal girders to impart strength and resistance to the hull was discarded, and a "bracket frame" system devised by Nathaniel Barnaby was adopted. This system allowed for the inclusion into the ship of a double bottom, with clear survival implications if damaged, while at the same time allowing for a saving in weight so that of the hull of Bellerophon weighed , versus for of . Some steel was used in the hull to save weight. HMS Bellerophon was ordered on 23 July 1863 from the Royal Dockyard in Chatham, Kent. She was laid down on 28 December 1863 and launched on 26 April 1865. The ship was commissioned