Smoothbore guns were the norm throughout the Napoleonic War and during the Crimean War 1853-6. The first operational use of rifled guns appears to have been in the Italian War of 1859 when employed by the French. In the following year the British used adapted Armstrong BL guns in China, which had been in service since 1858. The success of these guns in the field, led to the Royal Navy demanding a 7-inch breech loading gun for sea use. Up until 1863 some £2.5 Million was spent on developing new rifled breech loading guns by the British.
The Royal Navy took the 7-inch RBL gun into service in 1859 but by 1864 had had ceased to use them. The primary problem was the breech mechanism, and the limitations of these guns was highlighted by Japanese experience in the 1863 during the Shimonoseki campaign where they proved liable to failure.
Between 1863 and 1864 there was comparative test done with Armstrong breech and muzzle loading guns, and Whitworth muzzle loaders. The muzzle loading guns generally came out as superior to the breech loaders then employed.
Between 1864 and 1865 further tests were done with various 7-inch RML which resulted in the Woolwich RML gun being adopted. In 1865 an Artillery Committee unanimously endorsed the RML, and this was further reinforced with Committees in 1869 and 1870. Thus, the Rifled Muzzle Loader was adopted in preference to breech loading guns. In 1870 the Lord Northbrook, Under Secretary for War and his committee approved the use of 12-inch 35 ton and 12.5-inch 38-ton RML guns which were also used in some number for coastal defence batteries.
In 1875 further serious consideration was given to the RML guns when a 38-ton gun was fired successfully for two consecutive days. The Krupp equivalent gun cost twice a much as the RML gun, a major consideration. At this time the Russians had adopted the Krupp system while the Italians purchased Armstrong guns for their navy.
In 1874 to 1875 considerable advances had been made with propellants and slow-burning powder had been developed which could almost double the power of guns. The sheer size of the RML guns made them unsuitable for casemates and on ships, and hence considerations was once again given to using breech loading rather than muzzle loading guns.
In 1879 as 38-ton RML on HMS Thunderer exploded with serious loss of life. This was attributed to accidental double loading, something less likely with a breech loading gun. In 1881 to 1882 funds were allocated to produce 103 6-inch BL guns for sea service, eight 9.2-inch BL guns and ten 12-inch BL guns. Despite consideration at this time that an RML gun of a similar calibre was as effective as any equivalent calibre BL gun, other concerns can to the fore. Prime amongst these was that breech loading guns of similar calibre were small than rifled muzzle loaders and thus more BL guns could be carried on a ship than RML guns, thus increasing overall firepower for the same size of hull.
By 1881 therefore the British had accepted that a transition had to be made from Rifled Muzzle Loading guns to Breech Loading guns for both ship and for land use. (TNA WO 33/36)