68 - pounder gun The 68 - pounder cannon was an artillery piece designed and used by the British Armed Forces in the mid - 19th century . The cannon was a smoothbore muzzle - loading gun manufactured in several weights , the most common being , and fired projectiles of . Colonel William Dundas designed the 112 cwt version in 1841 and it was cast the following year . The most common variant , weighing 95 cwt , dates from 1846 . It entered service with the Royal Artillery and the Royal Navy and saw active service with both arms during the Crimean War . Over 2 , 000 were made and it gained a reputation as the finest smoothbore cannon ever made . The gun was produced at a time when new rifled and breech loading guns were beginning to make their mark on artillery . At first the 68 - pounder ' s reliability and power meant that it was retained even on new warships such as HMS " Warrior " , but eventually new rifled muzzle loaders made all smoothbore muzzle - loading guns obsolete . However , the large surplus stocks of 68 - pounders were given new life when converted to take rifled projectiles ; the cannon remained in service and was not declared obsolete until 1921 . Design . The cannon was designed in response to the need for heavier weaponry as armour on ships of the line improved . Colonel William Dundas , the government ' s Inspector of Artillery between 1839 and 1852 , designed the cannon in 1846 . It was cast by the Low Moor Iron Works in Bradford in 1847 and entered service soon after . Like numerous cannon before it , it was a cast iron smoothbore loaded from the muzzle . The cannon was relatively cheap to produce – the Royal Commission on the Defence of the United Kingdom estimated that each cannon cost approximately £167 . ( 2010 : £12645 ) . Over 2000 were cast before 1861 and its exceptional durability , range and accuracy earned it a reputation as the finest smoothbore cannon ever made . Operation . The gun was a traditional muzzleloader ; it needed to be loaded from the end of the barrel . Before it could be loaded the bore of the barrel was cleaned with a sponge , after which a propellant charge ( gunpowder in a cloth bag ) was rammed down into the breech . This was followed by a projectile , often encased in wadding . The gun was primed ( using a metal spike inserted through the vent that pierced the charge ) , and fired using a percussion cap ( which ignited the charge and forced the projectile out of the barrel ) . The 68 - pounder had an effective range of approximately , however at its maximum elevation of 15 degrees it had a maximum range of , a distance that the projectile would cover in 15 seconds . With a powder charge ( the " far " charge , although the gun was proofed to 25 lb charges ) the cannon fired a solid shot at a muzzle velocity of . The cannon could fire solid shot , explosive shells , grapeshot , case shot and molten iron shells ( thin walled shells filled with molten iron ) . Although the cannon ' s barrel bore was , both shot and shells were in diameter . This allowed a windage gap of around the projectile ; enough to aid the loading process , but not enough to seriously diffuse the propellant gasses . The official weight of the shot was listed at 68 lbs but in reality this varied according to the material of the shot itself ; cast iron shot weighed , wrought iron shot and steel shot weighed , and chilled steel weighed . It was estimated that one 68 - pound shot had the destructive power equivalent to five 32 - pound shot . The explosive shells were primed with of gunpowder . They were fitted with simple fuses that were ignited by the flash of the charge – early wooden fuses were eventually replaced by more reliable fuses designed by Captain Edward Boxer in 1849 . The gun crew still had to gauge the best length of fuse for the range they were firing – ideally the shell should explode just before hitting its target . To prevent the shell exploding in the barrel it was fitted with a sabot to ensure the fuse faced away from the charge . On land a minimum crew of nine men ( usually commanded by a non - commissioned officer ) was required to fire the gun , which was normally mounted on a traversing gun carriage . On board a ship the gun crew could be doubled to 18 men who needed to traverse the gun carriage by hand , using hand spikes and rope tackles . The extra crew was on account of the fact that sailing ships usually only fired their cannon from one side of the deck . In the unlikely event of both sides being in action at once , nine men would be detached to man the gun opposite . In both cases the gun was elevated using wooden wedges driven under the breech of the barrel by brute force . It was aimed using an advanced hexagonal sighting mechanism marked with the elevation on one face and the gun ' s range ( according to different weights of cartridge charges ) on the other five faces . Service . The cannon was put to use both on land and at sea . It was fitted to numerous Royal Navy warships of different sizes such as , , , and the " Conqueror " - class ships of the line . Several of these ships saw action during the Crimean War where the 68 - pounder was used extensively during the Siege of Sevastopol . Along with 32 - pounders and Lancaster guns they were taken from their ship mountings and dragged up to siege batteries by the Naval Brigade , from where they regularly bombarded Russian positions for the next year . The cannon was also fitted in large numbers to the " Aetna " - class ironclad floating batteries , although these had little impact on the war . Most notably the 68 - pounder was fitted to the s and . Originally it was intended to fit forty 68 - pounders , primarily on one gun deck , but this specification changed during their building and they were finally equipped with twenty - six 68 - pounders ( 13 on each side ) . Alongside these , the ships were equipped with new rifled breech loading Armstrong gun s of two types ; 7 inch and 40 pounders . Although the Armstrong guns represented a new direction in artillery , the breech loading mechanism meant that they were unable to withstand the explosion of a heavy cartridge . Smaller cartridge charges were therefore required and the gun ' s muzzle velocity suffered as a result . Ironically the Armstrong Guns were therefore incapable of penetrating the armour fitted to the " Warrior " - class ships , while the 68 - pounder ( with its high muzzle velocity ) could . As late as 1867 it was planned to fit the new s with 68 - pounders , but they were instead completed with a RML 7 inch gun and a RML 64 pounder 64 cwt gun . On land the 68 - pounder was used extensively in British coastal defences constructed during the 1850s - notably at forts like Gomer and Elson defending Portsmouth , and Forts Victoria , Albert and Freshwater Redoubt defending the Needles Passage . The 1859 Royal Commission envisaged arming the numerous new forts they proposed with the 68 - pounder cannon and costed for them accordingly . The introduction of the Armstrong gun initially led many to think that weapon would be used instead , but whilst the forts were being built , the Armstrong gun ' s weaknesses were exposed and the military reverted to using muzzle loaded weapons . However , the advantages of rifling and the Armstrong ' s wrought iron construction were retained , leading to a new design of artillery piece – rifled muzzle loaders . Conversion to rifled muzzle loader . The introduction of rifled muzzle loaders ( also classed as RMLs ) rendered smoothbore guns largely obsolete . However , the 68 - pounder and other smoothbores still existed in large numbers and various attempts were made to adapt the guns to fire new projectiles . Eventually Captain William Palliser patented a method of boring out the gun barrel and inserting a wrought iron rifled liner . This allowed rifled shot and shells to be fired from old smoothbore cannon and experiments revealed that it made them even more powerful than they had been before . Introduced in 1872 , 68 - pounders adapted in this way had a calibre of and were known as a RML 68 - pounder , or officially as the RML 80 - pounder 5 ton . With a powder charge they could fire an projectile at a muzzle velocity of . They were deployed as coast defence and garrison artillery around the British Empire and remained in service until eventually declared obsolete in 1921 . At least two 68 pounders were converted to 7 inch 6 . 5 tons RML guns firing a 115 lb or 150 lb double shot .