1887: 45.0 cm RML 17.72 inch 111 Ton Mk I 'William Armstrong' Elswick Gun
RML = Rifled Muzzle Loading
Weight 102 tons (average)
Length (oa) 32 ft 7.85in (391.85 in)
Length (bore) 20.5cal (363 in)
Diameter 76.45in (max) 29 in (at muzzle)
Chamber Size 59.72 x 19.7 in, volume 17 049 cub in
Projectile Weight 2000 lb (including 24 lb gas check)
Charge 450 lb prismaticl or prismaticl black (4 x 11 N)
Muzzle Velocity 1548 ft/Sec
Rifling Length 302.88 in, twist 1 in 105 to 1 in 50 at 2.88in from muzzle then uniform, 28 grooves, polygroove plain section 0.125 x 1 in, lands 0.888 in
17.72 Inch RML
Details of the 17.72 Inch RML Mark 1
The Italian battleship ‘Duilio’
17.72 inch RML Mk I The origins of this gun go back to the Duilio and Dandolo, two of the remarkable but not entirely satisfactory ships designed by Benedetto Brin for the Italian Navy. When authorized in 1872 it was intended that they should have four 35 ton guns but in 1873 this was increased to four 60 ton. Both ships were laid down in the first half of that year but in 1874, as a consequence of the intention to arm the Inflexible with four 80 ton guns, it was decided that the two Duilio's should each have four 100 ton guns. A contract to build 8 of these guns was placed with Armstrong's at Elswick in July 1874, though only one was to be made initially, the others following when the first had been found satisfactory. It must be noted that the Duilio was about 900 tons smaller than the 11 8 8 0 ton Inflexible and that her beam was only 64 ft 8in compared with 75ft in the latter ship. She was clearly much overgunned as is shown by her ammunition outfit of only 35 rounds per gun.
The first gun, bored to 17 in and not chambered, was sent to Italy for trials in July 1876 but, on satisfactory reports of the 80 ton gun, orders to proceed with the other 7 guns of the original contract had already been given on 23 June 1876. As an unchambered 17 in, 1542 ft/sec MV was attained with a 20001b projectile and a 3751b prismatic black charge. Other tests were satisfactory and the gun was returned to Elswick for boring to 17.72 in and chambering. Further trials were carried out in March and April 1878 and the four guns for the Duilio were delivered in time for her to complete in January 1880, the Dandolo, which had been launched 26 months after the Duilio, following in April 1882. Meanwhile the British wished to increase the coast defenses of Gibraltar and Malta and, as further 16 in RML’s could not be delivered from Woolwich in reasonable time, it was decided to break their monopoly and order 4 of the 17.72in from Elswick which, at that time, had a far better equipped gun-
The construction was very different from that of the 16in RML. The steel 'A' tube was in two lengths joined by a steel ring, in halve s, over the j oint. Over the 'A' tube were shrunk 10 wrought iron coils, identified from the breech end as 2A, 213, 2C, 21), 2E, 21)1, 2E1, 2F, 2G and 2H. The 2D and 21)1 coils were thinner than the rest and had the 2E and 2E' coils shrunk over them. The next layer, which stopped 207.85in from the muzzle, comprised the 3A and 3B coils, the trunnion piece and the 3C coil. Finally there was a layer extending to the trunnions, consisting of the 4A', 4A and 4B coils. The cascable, which screwed into the 2A coil, contained the axial vent and was made from a wrought iron forging as was the trunnion piece. The various parts were shrunk to more precise limits than in the Fraser construction as it was attempted to give each the designed stress. The surface of some of the coils was serrated to give a better longitudinal grip, but not all the coils had overlapping joints, and it was thought that the 'A' tube took by far the greatest part of the longitudinal stresses.
It will be noted that the projectile was relatively light as, if scaled up from the 16 in, it would have been about 2300 lb. Much heavier charges were used by the Italians and in trials 1725 ft/sec MV was attained with a 2000 lb projectile and a 573 lb charge but on 6 March 1880 one of the Duilio's guns pulled apart. The fracture ran from the front end of the parallel part of the chamber to the front end of the 4B coil just behind the trunnions. The charge on this occasion was 551 lb of Fossano powder, which had large irregular grains each containing a number of small high density pieces in a lower density material. Normally such a charge would have given about 17.4 tons/sq in but it was believed that the Fossano grains had broken into fine pieces which would have given a much higher pressure. The gun was repaired by building up on a new A tube and subsequently the Italians appear to have limited charges to 529 lb, which gave about 1700 ft/sec MV, while in Britain a much smaller charge and lower performance was accepted.
The British projectiles were of the same type as those for the 16 in, the Paffiser AP being 48.6in long with a 32 lb burster and the cast iron common of the same length having a 78 lb burster. A later cast steel common shell had a 194 lb burster and was 52.55 in long.
The two Gibraltar guns were mounted at 'Victoria' and 'Napier' of Magdala's batteries and the two Malta guns at 'Rinefla' and 'Cambiidge' batteries. They were in the usual type of coast defense carriage-
Note About These Images
The 111 ton gun is also known as the RML 17.72 inch Mark I naval gun. It was mounted on the Duilio and Dandolo, two of the remarkable but not entirely satisfactory ships designed by Benedetto Brin for the Italian Navy as well as the HMS Benbow (1885) and a few other ships. The carriage shown above and to the right are a proof mount on a railway carnage; it was not an official railway gun.
The railroad and engineering journal Year: 1887
THE ENGLISH 111 -
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