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. Ammunition This was a second-generation RML gun, equipped with polygroove rifling and firing only studless ammunition with automatic gas-checks for rotation. Projectiles were of three types, all weighing and having a diameter of 17.7 inches (450) mm: Armour-piercing (AP) Palliser, 44 inches (1.12 m) long, steel forward section, capable of piercing 21 inches of steel at 2,000 yd (530 mm at 1,800 m). with a 32-pound (14.5 kg) explosive internal charge. High explosive (HE) Common, long, with thinner walls and a HE charge. Shrapnel shell: long, with a charge of only HE, but also 920 bullets of each. 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 remaining energy. Service 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, Italian admirals called for even more powerful guns, to hold the lead in battleship design. 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. During firing trials on 5 March 1880, one of Duilios 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