The RML gun is a step in the evolution of artillery. In 1859 William Armstrong introduced the rifled breech loading gun. This gun was a major break through from the smooth bore guns which it was designed to replace. Loading from the breech (rear) was safer for the gunners and cylindrical shell and rifling in the barrel produced a more accurate gun firing to a greater range. The Armstrong guns were far from popular with the gunner community and a number of incidents resulted in it being superseded with the older muzzle loading guns but the rifling and cylindrical shell being retained. New guns were produced but as there were a large number of smooth bore muzzle loading guns still available, Sir William Pallister devised a method of converting these guns by boring out the cast iron guns to form a casing, and then inserting a coiled wrought iron barrel, kept in position by an iron collar and screw plug. The successful system was adopted in 1863. To differentiate between the guns the converted guns were classified as RML (Rifled muzzle loading) and the new guns as MLR (Muzzle Loading Rifled). The term RML is now the commonly used name to identify all these guns.