The 15 guns Armstrong made were used to arm two Italian battleships and, to counter these, British fortifications at Malta and Gibraltar.

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 (410 mm) of mild steel at 2,000 yards (1,800 m).

Armstrong, the main British artillery producer, began a project for creation of an even larger weapon, an 18 in (460 mm) gun, also called the '100 ton'.

Armstrong offered it to the Royal Navy, which rejected the gun, deeming it too heavy and costly.

[7] The gun was built up from an inner steel tube surrounded by multiple wrought iron coils.

When it reached the back of the gun it would unleash a powerful jet of water to clean the barrel and make sure no fire was left.

[10] This was a second-generation RML gun, equipped with polygroove rifling and firing only studless ammunition with automatic gas-checks for rotation.

They were made of 1 cwt (51 kg (112 lb)) 'Large Black Prism' propellant, and four or five were needed for every shell fired at maximum power.

The recoil was 1.75 m (5 ft 9 in) as two hydraulic pistons in the rear part of platform absorbed the remaining energy.

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.

On 21 July 1874, Armstrong signed a contract with Italy to deliver eight of its 100-ton guns, enough to arm Duilio and her sister-ship Dandolo.

This was a steam driven hydraulic crane designed by George Wightwick Rendel, the first of Italy.

The setup with the pontoon was inspected by George Rendel and Captain Noble, partners in the Armstrong firm.

However, the projectiles went straight through with a remaining velocity of about 600 feet per second (180 m/s) and made a very large rent in the iron plates.

[17] In mid-November 1876, Nathaniel Barnsby, Director of Naval Construction to the Royal Navy was to go to La Spezia to study the results and the merits of using steel.

The highest observed pressure was 20.8 ton per square inch or 3,170 atm with a charge of 330 pounds (150 kg) and a velocity of 443 m/s.

There were three goals: First to collect ballistic data while firing with the British powder, and compare this with the data of the original gun; Secondly to test the Italian Fossano gunpowder and compare it with the English P2 powder; Thirdly, to determine the best form of cartridge and the best means to ignite it.

[22] With the proper charges and a projectile of 2,000 pounds (910 kg), the original gun had given a velocity of 1,424 feet per second (434 m/s) at a pressure of 18.3 tons per square inch.

On average, the Fossano gunpowder increased the energy of the gun by about three percent while it reduced pressure by about 4 tons per square inch.

The Italian contract shocked British authorities, who had the Malta naval base to defend.

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 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).

In December 1877, Simmons, chief of Malta defenses, was called to London to discuss the issue.

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.

[23] Four guns were requested in March 1878 and manufacture started in August; in the meantime Duilio had been conducting sea trials since 1877.

HMS Stanley, a cargo vessel specially adapted for the task, delivered Malta's two guns.

Between 1887 and 1888 activity stopped due to the need to rework hydraulic systems, but nevertheless the guns were considered quite reliable, serving for more than 20 years.

During the First World War the guns at Malta were supposedly made ready for use when SMS Goeben was known to be nearby.

The gun at Victoria Battery was moved to Napier, which the military deemed the more effective site.

Fort Rinella is under the guardianship of Fondazzjoni Wirt Artna - the Malta Heritage Trust.