| RML 17.72 inch (450 mm) gun | |
|---|---|
"Rockbuster" at Napier of Magdala Battery, Gibraltar |
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| Type | Naval gun Coast defence gun |
| Place of origin | United Kingdom |
| Service history | |
| In service | 1877-1906 |
| Used by | United Kingdom Italy |
| Production history | |
| Designer | Elswick Ordnance Company |
| Unit cost | £16,000[2] |
| Number built | 15[1] |
| Specifications | |
| Weight | 103 tons |
| Barrel length | bore : 362.9 inches (9.22 m) (20.5 calibres)[3] |
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| Shell | HE, AP, Shrapnel, 2,000 pounds (910 kg)[3] |
| Calibre | 450-millimetre (17.72 in)[3] |
| Recoil | 1.75 m |
| Elevation | 10° 30' |
| Traverse | 150° |
| Muzzle velocity | 1,548 feet per second (472 m/s)[4] |
| Maximum range | 6,600 yards (6,000 m) |
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. They were mounted on two Regia Marina battleships, and also in fortifications at Malta and Gibraltar.
Contents |
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) and 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'. It was proposed to the Royal Navy, but rejected because it was considered too heavy and costly.
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 of them 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.
Armstrong was ready to sell those guns, with a contract for eight units of 450-mm calibre, enough to arm the Duilio and her sister Dandolo. This happened 21 July 1874.
These new artillery pieces were enormous weapons for their time (their weight was comparable to the Iowa-class 406/50 mm), even though the barrel was quite short. They were muzzle-loading guns, with rifled tube and rigid mount.
The gun was 9.953 m long. Its maximum diameter was 1.996 m, but it reduced to 735 mm at the muzzle. The construction method of an inner steel tube surrounded by multiple wrought iron coils[5] was very complex, with several structures containing one another. The internal barrel was 30 feet 3 inches (9.220 m) long, or 20.5 caliber.
Firing was mechanical or electrical, with an optical system for aiming. Projectiles were of three types, all weighing 2,000 pounds (910 kg) and 17.7 inches (450) mm diameter:
Projectiles could be exploded by timer or via 15-second fuses.
Launch charges were polygonal, 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.
Projectiles could be fired only once every four minutes. Muzzle velocity was 472 m/s and maximum elevation was 10° 30' (direction was 150 degrees). At maximum charge (204 kg?) and maximum elevation it could achieve only 5,990 m range, but at that distance it could still pierce 394 mm of steel (it is not clear if it was mild or hardened).
The weight of the mount was: 103,888 kg (gun), 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.
The recoil was 1.75 m and two hydraulic pistons in the rear part of platform absorbed the rest of energy. Rotation was obtained with chains powered by hydraulic systems, and another hydraulic system was used for elevation.
Crew was 35, including 18 for ammunition depots.
This contract shocked British authorities, as they had the Malta naval base to defend. At that time, (after the Suez Canal), Malta was the most important British base in the Mediterranean. Even if many coastal fortresses were armed, even with 320 mm guns, this left Malta poorly defended against a possible attack from Duilio-class ships. This was a worrying problem also because Crispi called Malta 'Italia irredenta' ('Unredeemed Italy').
The British feared that the Duilios could reach Valletta port and start to fire on their fortresses, destroying them one after the other, while keeping outside the effective range of the fort's guns (these battleships were also well protected). But the requests made by the British Army had no effect on London bureaucracy, and until the Duilio was launched in May 1876, no decision was made.
At that time, the Royal Navy started to take care of this issue (already signalled by the British Army) and asked for a gun capable of piercing 36-inch steel at 1000 yd (900 mm at 900 m). Several design were proposed for immense guns of 163, 193 and 224 tons.
In December 1877, Simmons, chief of Malta defenses, was called to London to discuss this issue and he asked for four guns comparable to Duilios at 3,000 yards. Strangely enough, apparently nobody had thought to forbid Armstrong to sell to Italy these much-feared weapons that were completed and sold regularly, rather than embargoed.
Due to the emergency, it was decided that it would be simpler to quit designing the bigger guns and buy the same weapons as the Duilios, because, generally, a land fortress with the same caliber guns has an advantage compared to a ship.
Four guns were requested in March 1878 and construction was started in August, while in the meantime Duilio had been conducting sea trials since 1877.
The career of these guns was not impressive, as no Italian battleship had ever threatened Malta. When Gibraltar commanders heard of these big guns they asked for some, and obtained them: two of the four ordered for Malta were delivered there.
The first battery was Napier of Magdala, on Rosia Bay, Gibraltar, and the second, called Victoria, was placed one kilometer north.
Construction started in December 1878, with the first ready in 1883 and the second in 1884. At that time, the Duilio-class ships had been operational for around seven years, leaving a gap in Malta defenses.
The first gun was transported by HMS Stanley (a special cargo vessel) adapted for the task and delivered on 19 December 1882. The second was delivered 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 Malta guns were placed on Fort Rinella, completed in 1884, and Fort Cambridge, ready in 1880. The first ammunition load comprised all the models available, included 50 AP and 50 HE. Shrapnel, once fired, was not replaced, being considered not so effective.
Stanley delivered two guns: Rinella received its on 31 July 1883 and mounted it 12 January 1884, and Cambridge respectively on 16 September 1882 and 20 February 1884.
The work to make these machines serviceable was so great that until 1885 there were no firing tests. Between 1887 and 1888 the activity was stopped due the need to rework hydraulic systems, but nevertheless these guns were considered quite reliable, serving for more than 20 years.
Another problem took place: 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.
One of the British guns was also cracked: Napier gun, during a fire trial, had the barrel cracked, it this case because the crew managed to fire one shot for every 2.5 minutes. This wrecked gun was not easily repairable; it was used as a foundation for a building, and was replaced with the other, because Fort Napier was deemed more effective. The Malta guns were phased out in 1906, as was Napier's. They had fired their last shots several years before, in 1903 and 1904. During the First World War the guns at Malta were claimed to have been ready for use when SMS Goeben was known to be nearby. Although the 100 t guns were powerful, they would have been totally outclassed by modern weapons: the range and rate of fire were too low, as modern 280–305 mm guns had over 15–20 km range and the rate of fire of one shot every 30 seconds. Goeben would have had no difficulty firing against Malta guns, if needed.
Napier and Rinella's guns are still intact. They were too costly to demolish and were left as junk, then later restored to acceptable condition. The 'pink' paint was added only recently; originally they were not painted at all.
Rinella Fort also exists today, and is under the guardianship of Fondazzjoni Wirt Artna - the Malta Heritage Trust. It was 71 m by 66 m, with an external wall 6 m tall. There were two floors, the lower had an ammunition depot, and also shaft motors to power the hydraulic systems. The large fixed barrette that contained the gun was 127 mm thick iron, with several 510 mm windows to reload the gun (by muzzle) with special reloading systems, directly from the ammunition depots in the lower floor.