RML 17 . 72 inch gun The RML 17 . 72 inch ( 450 mm ) guns ( " 100 - ton gun " ) were rifled muzzle - loading guns made by Elswick Ordnance Company in the United Kingdom . The 12 guns Elswick made armed two Italian battleships , and to counter these , British fortifications at Malta and Gibraltar . Origins . Around 1870 the largest gun made by UK firms was the 320 mm RML ( rifled , muzzle loading ) gun , with a mass of 38 long tons ( 38 . 6 t ) , firing an 818 pound ( 371 kg ) projectile capable of piercing 16 . 3 inches ( 414 mm ) of mild steel at 2 , 000 yards ( 1 , 800 m ) . This weapon was adequate for the needs of the time , but the progress of gun technology was very rapid . French industries soon made a 420 mm , 76 tonne gun . This led the Royal Navy to ask for an 80 long ton ( 81 t ) gun . Armstrong , the main British artillery producer , began a project for creation of an even larger weapon , an 18 inch ( 457 mm ) gun , also called the ' 100 ton ' . Armstrong offered it to the Royal Navy , which rejected the gun , deeming it too heavy and costly . One - hundred ton gun description . These new artillery pieces were enormous weapons for their time . Their weight was comparable to that of the " Iowa " - class 406 / 50 mm , even though their barrels were quite short . They were muzzle - loading guns , with a rifled tube and rigid mount . Each gun required a crew of 35 men , including 18 men to handle the ammunition . The gun was 9 . 953 m long . The barrel ' s maximum diameter was 1 . 996 m , which reduced to 735 mm at the muzzle . The construction method of an inner steel tube surrounded by multiple wrought iron coils , was very complex , with several structures containing one another . The internal barrel was 30 feet 3 inches ( 9 . 220 m ) long , or 20 . 5 calibers . The weight of the gun was 103 , 888 kg , or about 100 tons . Firing was mechanical or electrical , with an optical system for aiming . Projectiles were of three types , all weighing 2 , 000 pounds ( 910 kg ) and having a diameter of 17 . 7 inches ( 450 ) mm : Firing charges were polygonal in shape , with 399 x 368 mm maximum width and length . They were made of 1 cwt ( 51 kg ) ' Large Black Prism ' propellant , and four or five were needed for every shell fired at maximum power . The recoil was 1 . 75 m as two hydraulic pistons in the rear part of platform absorbed the rest of energy . The gun crews could only fire a projectile once every four minutes . Muzzle velocity was 472 m / s and maximum elevation was 10° 30 ' . At maximum charge ( 204 kg ? ) and maximum elevation , a projectile could achieve a range of only 5 , 990 meters , but at that distance the projectile could still pierce 394 mm of steel ( it is not clear if it was mild or hardened ) . Projectiles could be exploded by timer or via 15 - second fuses . The weight of the mount was : 20 , 680 kg ( mobile mounts with 18 wheels ) , 24 , 118 kg ( platform ) and 2 , 032 kg ( base ) . The platform was sloped at 4 degrees to slow the recoil . On the platform mount , hydraulic systems powered chains that traversed the guns through an arc of 150 degrees ; another hydraulic system provided elevation . Sale to Italy . After the reunification of Italy , the Regia Marina began an innovative program to field the best and most powerful battleships of the time , the first being the " Duilio " - class , armed with 380 mm guns . They were already very powerful , but in February 1874 when the UK started to build HMS " Inflexible " , armed with 406 mm guns , Italia n admirals called for even more powerful guns , to hold the lead in battleship design . Armstrong was ready to sell those guns . On 21 July 1874 it signed a contract with Italy to deliver eight of its 100 - ton guns , enough to arm the " Duilio " and her sister - ship " Dandolo " . During firing trials on 5 March 1880 , one of " Duilio " s guns cracked while firing at the maximum charge . At the suggestion of the British Army , it was officially established that the maximum practical charge was 204 kg and not 255 . British response . The Italian contract shocked British authorities , who had the Malta naval base to defend . The opening of the Suez Canal ) in 1869 had rendered Malta the most important British base in the Mediterranean . Although Malta ' s defenses included 320 mm guns , this left Malta poorly defended against a possible attack from " Duilio " - class ships . This was a worrying problem because Francesco Crispi , one of the key architects of the Italian reunification , had called Malta " " Italia irredenta " " ( " Unredeemed Italy " ) . The British feared that " Duilio " and " Dandolo " , which were already well - armored , could fire on Malta ' s shore batteries , destroying them one after the other , while keeping outside the effective range of the batteries ' guns . But the British Army ' s concerns had no immediate effect on London bureaucracy ; until the Italians launched " Duilio " in May 1876 , London made no decision . Then the Royal Navy finally responded , requesting proposals from British arms manufacturers for a gun capable of piercing 36 - inch steel at 1000 yd ( 900 mm at 900 m ) . The manufacturers returned with designs for immense guns of 163 , 193 , and 224 tons . In December 1877 , Simmons , chief of Malta defenses , was called to London to discuss the issue . He asked for four guns comparable to " Duilios " at 3 , 000 yards . Due to the emergency , it was decided that the fastest and simplest solution was to quit designing the bigger guns and to buy the same weapons as those on " Duilio " , because generally a shore battery with the same caliber guns as a vessel retains an advantage over the vessel . Four guns were requested in March 1878 and manufacture started in August ; in the meantime " Duilio " had been conducting sea trials since 1877 . When Gibraltar ' s commanders heard of these big guns they too asked for some , which they obtained . Two of the four guns ordered for Malta would go to Gibraltar instead . Malta service . HMS " Stanley " , a cargo vessel specially adapted for the task , delivered Malta ' s two guns . One gun was placed in Fort Cambridge , which was ready in 1880 , and the other in Fort Rinella , which was completed in 1884 . Cambridge received its gun on 16 September 1882 but only mounted it on 20 February 1884 . Rinella received its on 31 July 1883 and mounted it on 12 January 1884 . By this time , the " Duilio " - class ships had been operational for around seven years . The work to make these machines serviceable was so great that until 1885 there were no firing tests . The first ammunition load comprised all the models available , included 50 AP and 50 HE . Shrapnel , once fired , was not replaced , being considered less effective . Between 1887 and 1888 activity stopped due the need to rework hydraulic systems , but nevertheless these guns were considered quite reliable , serving for more than 20 years . The career of these guns was not impressive , as no Italian battleship had ever threatened Malta . The Malta guns were phased out in 1906 , as was the remaining gun at Gibraltar . All had fired their last shots several years before , in 1903 and 1904 . During the First World War the guns at Malta were supposedly made ready for use when SMS " Goeben " was known to be nearby . Although the 100 t guns were powerful , modern weapons would have totally outclassed them : the range and rate of fire were too low , as modern 280 – 305 mm guns had a range of over 15 – 20 km range and a rate of fire of one shot every 30 seconds . " Goeben " would have had no difficulty firing on Malta ' s guns , if needed . Gibraltar service . The first battery built for the guns in Gibraltar was Napier of Magdala , on Rosia Bay , and the second , called Victoria Battery , was placed one kilometer north . Construction started in December 1878 , with the first ready in 1883 and the second in 1884 . " Stanley " also delivered Gibraltar ' s two guns . The first gun arrived on 19 December 1882 and the second on 14 March 1883 . These two guns were ready on their mounts on July and September 1883 . The first firings took place in 1884 , but the weapons were not fully operational until 1889 due to hydraulic system problems . The barrel on the gun at Napier cracked during firing trials ; this was because the crew had managed to stress the gun by firing one shot every 2 . 5 minutes . The wrecked gun was not easily repairable so it was used as a foundation for a building . The gun at Victoria Battery was moved to Napier , which the military deemed the more effective site . The two surviving guns . The guns at Napier of Magdala Battery and at Fort Rinella are still intact and one can visit them . The guns were too costly to demolish and were left as junk , but both were later restored to display condition . Fort Rinella is under the guardianship of Fondazzjoni Wirt Artna - the Malta Heritage Trust . The pink paint on the Fort Rinella gun was added only recently ; originally they were not painted at all .