RML 64-pounder 58 cwt
The RML 64-pounder 58 cwt guns (converted) were British rifled muzzle-loading guns converted from obsolete smoothbore 32-pounder 58 cwt guns. Design. When Britain adopted rifled ordnance in the 1860s it still had large stocks of serviceable but now obsolete smoothbore guns. Gun barrels were expensive to manufacture, so the best and most recent models were selected for conversion to rifled guns, for use as second-line ordnance, using a technique designed by William Palliser. The Palliser conversion was based on what was accepted as a sound principle that the strongest material in  the barrel construction should be innermost, and hence a new tube of stronger wrought iron was inserted in the old cast iron barrel, rather than attempting to reinforce the old barrel from the outside. This gun was based on the cast-iron barrel of the Dundas Pattern 32-pounder 58 cwt gun, which previously fired a 32-pound solid shot. The gun was bored out to 10.5 inches and a new built-up wrought iron inner tube with inner diameter of 6.29 inches was inserted and fastened in place. The gun was then rifled with 3 grooves, with a uniform  twist of 1 turn in 40 calibres (i.e. 1 turn in 252 inches), and proof fired. The proof firing also served to expand the new tube slightly and ensure a tight fit in the old iron tube. Ammunition. The 64-pounder used three types of ammunition. This ammunition was common to the other natures of 64 pounder gun - the 71 cwt converted gun and the 64 cwt gun. Although many guns were sited on coastal artillery positions, their effectiveness again armour of heavily armoured ships was limited. Common shell could be used against buildings or fortifications, shrapnel shell (for use  any Infantry or Cavalry) and case shot (for close range use against 'soft' targets. Ignition was through a copper lined vent at the breech end of the gun. A copper friction tube would be inserted and a lanyard attached. When the lanyard was pulled the tube would ignite, firing the gun. A number of different fuzes could be used enabling shells to either burst at a pre-determined time (and range), or on impact. Guns were fired using a silk bag containing a black powder propellant. A typical rate of fire was one round every three minutes. Deployment. This nature  of gun was designed for both land and sea service, though for the latter it was increasingly obsolete not long after introduction. It was used widely all across the British Empire. It did see Naval Service (NS) with the Naval Forces of the Colony of Victoria in Australia aboard the ex Ship-of-the-Line Nelson. To maintain maximum capability the gunners aboard the Nelson were drilled for both Smooth Bore and Rifled ammunition, and so the guns retained the original Millar Pattern sights as well as having one set of R.M.L. sights placed to the right of the centre  line - otherwise the sighting arrangement normally used in British service was a single set of R.M.L. sights on the centre line. The mountings used on this vessel were Wood Naval Standing Carriages. The gun mountings for coast defence in both British and colonial locations varied enormously. Carriages in both wood and iron varied in complexity – from a simple wooden garrison carriage, right through to some guns mounted on Moncrieff Disappearing gun carriages. Some, such as the depressing type carriages at Gibraltar were unique to their location. Some mountings were designed on mountings which provided some protection for their crews. Many  were mounted on wooden garrison carriages on open platforms and were used for gun drill, as well as range practice. They became obsolete for coast artillery use in 1902, whereupon many were scrapped and disposed of.