1870: 40.6 cm RML 16 inch 81 Ton Mk I 'Woolwich Gun'
RML = Rifled Muzzle Loading

To our Victorian forebears, bigger was most definitely better. Britain’s largest guns of this era were designed for shipboard use aboard the Royal Navy’s latest warships, and only later considered for railroad mounting.

The following gun from Woolwich Dockyards makes interesting reading; a colossal piece of firepower - an 81-ton gun, destined for one of the Royal Navy’s new fleet of ironclads, the HMS Inflexible. Ironclads were the spearhead of the arms race of the day: immense warships, housing heavily armored ‘citadels’ in their centers and carrying the largest guns that could be made at the time.

The 81-tonner was indeed large. The Engineer notes that only two years  previously, the largest gun yet made weighed 35 tons, and had been nicknamed ‘The Woolwich Infant’; it was ironic, the report says, that the new weapon did indeed make this one look child-sized. The 81-tonner was 27 feet long and was made with a 14-inch caliber; but the metal of the barrel was so thick that the caliber was increased to 16 in to accommodate the rifling needed to stabilize the flight of its shells, which the article estimates would weigh some 1200 lb. This would be fired 450 pounds of gunpowder with a muzzle velocity of 1300 ft per second, imparting enough energy to penetrate 23in of forged-iron armor plate at 1000 yards.

Inflexible was a pioneer in other senses too; it was the Navy’s first ship to be completely lit with electricity (and subsequently the first to see a fatal electrocution), and also the first with underwater torpedo tubes. She served for almost 40 years, and was finally scrapped in 1903.

The Inflexible was intended to counter new Italian warships which threatened British bases in the Mediterranean. It was equipped with four 81-ton guns, which were so big they could not be reloaded from within their turrets; instead, a muzzle-loading device equipped with hydraulic rams was mounted on the deck, which were forced inside the barrel twice, firstly to extinguish burning material, and secondly to push the shell and its gunpowder charge into the gun; this operation took four minutes. The guns saw action with Inflexible at the bombardment of Alexandria in 1882, when they fired 88 shells.

Inflexible’s 81-ton gun, pictured in reloading position

HMS Inflexible, in 1886

The origins of this gun go back to July 1873 when the Admiralty requested the War Office, at that date responsible for the supply of naval guns, to prepare a design for a 60 ton gun, 22 ft 4 in in overall length. The largest gun actually in British service at this time was the 12 in/35 ton. At a meeting on 21 October 1873 a design for a 75 ton 16 in of the above length, to fire a 1650 lb projectile with a 300 lb black powder propellant charge, was discussed and a requirement to pierce 20 in of wrought iron at 1000 yds was mentioned; the Italian battleship Duilio, laid down in April 1873, would have armour of this thickness, as also, it was erroneously believed, would the Russian battleship Petr Veliki, launched in August 1872. On 26 November 1873 a less ambitious design was produced for a 60 ton 15 in gun, still 22 ft 4 in long, firing a 1350 lb projectile with 230 lb charge. Finally, on 11 March 1874, the manufacture of an experimental gun of about 75 tons - on a later estimate 80 tons - was approved. This was to have a 24 ft bore and was to be tried successively at 14, 15 and 16 in cal - when bored to 16 in, it was expected to give an MV (muzzle velocity) of 1400 ft/sec with a 1650 lb projectile and a 300 lb propellant charge. It took 18 months to complete this gun, as enlarged plant had to be acquired at Woolwich, and meanwhile the Inflexible, which was to mount 4 of these guns when the design had been settled, had been laid down on 24 February 1874.

The experimental gun was eventually bored to 14.5in, not 14 in, and rifled on the unsatisfactory but usual RML system with 11 grooves, studded projectiles and the twist increasing from zero to 1 in 35 at the muzzle. It was 'proved' on 17 September 1875 attaining an MV of 1550 ft/sec with a 1260 lb projectile and a 240 lb charge. After further firings it was bored to 15 in and rerifled, then chambered to 16 in and finally bored to 16 in and rerifled. It should be noted that in the later firings copper gas-checks were used. These were rimmed discs attached to the base of the projectile; the rim expanded into the rifling grooves on firing so that the serious erosion from powder gases escaping past the projectile was greatly reduced. After a total of 166 rounds the gun was examined on 30 December 1876 and it would found that the steel tube had cracked in a rifling groove for a length of 55 to 85 ins from the bottom of the bore. This was thought to be due to holes drilled and tapped for the fitting of crusher gauges to measure the pressures in the bore on firing.

However, firings continued, with some further development of the crack, and the gun was then chambered to 18 in diameter and attained an MV of 1600 ft/sec with a 1700 lb projectile and 425 lb charge. By June 1877 the total of rounds fired was 274 but, though the Inflexible had been launched on 27 April 1876 and construction of all 4 of her guns was under way in March 1877, important details were as yet unsettled. In particular it had not been decided whether to abandon the studded projectile in favor of an improved gas- check combined with shallower but more numerous rifling grooves, a system to be known as polygroove. Accordingly the first of the Inflexible's guns was bored to 15.5 in and given polygroove rifling but troubles with excessive pressures and shells ,setting up' occurred so it was not until August 1878 that it was recommended that this system should be used with a bore of 16 in. It had been decided a year previously that the guns were to be chambered. The Inflexible's 4 guns were completed in 1880-1881 and this much delayed ship was finally ready in October of the latter year. Two more guns completed in 1881-1.882 were mounted in a twin turret at Dover and one more, intended as reserve for the Inflexible, was completed in 1885-1886 to give, with the original experimental gun, a total of eight.

All were built at the Royal Gun Factory Woolwich which at that date had a monopoly of gun construction for the British Services. The 16 in RML was built on what was known as the Fraser two layer modification. There was a steel W tube which was heat-treated and quenched in oil but not tempered, and over this a wrought iron breech piece, 1B coil, 2B coil and B tube were shrunk. These were linked to one another by overlapping bayonet type joints. The C coil, incorporating the trunnion ring, was shrunk over the breech piece and part of the 1B coil and the cascable screw, which contained the axial vent, was screwed into the breech piece and butted firmly onto the end of the W tube. The cascable and trunnion ring were wrought iron forgings while the other parts were built up by hammer welding two or more coils"themselves made by coiling wrought iron bar over a mandrel and hammer welding.

No attempt was made to carry out the shrinking so as to give precise calculated stresses in the various layers. This construction was crude but cheap, and reasonably effective for relatively short guns, and gave better longitudinal strength than the more complex Armstrong construction used in the 17.72in RML.

Weight 80 tons (average)

Length (oa) 26 ft 9 in (321 in)

Length (bore) 18 cal (288 in)

Diameter 72 in (max) 25 in (at muzzle)

Chamber size 59.6 x 18 in, volume 14 600 cub in

Projectile Weight 1700 lb (including 21 lb gas check)

Charge 450 lb prismatic black (4 x 112.5), later 450 lb prismatic brown

Muzzle Velocity 1604 ft/sec with black powder, 1540 with brown.

Rifling Length 227.4in twist 0 to 1 in 50 at muzzle, 33 grooves, polygroove plain section 0. 1 x 1 in, lands 0.523 in

16 Inch RML

Details of the 16 Inch RML Mark 1

Brown powder charges were approved in April 1885 as black powder was found to expand the A tube and, in one instance, to crack it. The two Dover guns, Nos 6 and 7, were identical to the others except for shorter trunnions. A report of 23 May 1888 shows no available reserve guns for Inflexible as No 4 had had to be replaced by No 8 and neither No 4 nor the original No 1 were yet repaired. Two years later it was suggested that the two Dover guns might be replaced by smaller BL’s and transferred to the Navy as additional reserves but nothing came of it, perhaps because the trunnions would have had to be lengthened. The life of the 16 in RML before relining was rather dubiously estimated at 350 rounds. The Inflexible's two twin turrets allowed 10' elevation and 2' to 5' depression depending on the training angle with fixed loacling positions at 9' 35" depression. The hydraulic loading gear could accommodate a shell 60in long which gave ample margin as the longest common shell was a little under 51 in and the chilled iron Palliser AP (Armour Piercing) 43.45 to 43.7in. At 10' elevation the range at 1590 ft/sec MV was 6730 yds, reducing to 6430 yds at 1540 ft/sec.

The Inflexible took part in the bombardment of Alexandria on 11 July 1882. At that date her outfit per gun was 55 Palliser AP, each with a 161b black powder burster intended to explode on impact as there was no fuse, 15 nose fused cast iron common shell each with a 601b black powder burster, 5 shrapnel, containing 860-4oz shot, and 5 case, intended mainly for use against torpedo boats and containing 1920-8oz shot. Her total expenditure in the bombardment was 21 Palliser, 56 common and 11 shrapnel, all fired with full charges. The Palliser AP was unlikely to burst unless it struck a heavy gun or mounting and the effect of the other projectiles was much reduced by the near uselessness of the fuses for which the War Office authorities were responsible. Cast steel base fused common shell, with 112.75 lb black powder bursters, did not become available until much later.

The next heaviest RML in the British Navy was the 12.5 in/38 ton so the 16in was by far the largest. It can be judged as an interesting and fairly satisfactory gun but of obsolescent type by 1881 when it entered service, as two years previously a 15.75 in/21.8 cal Krupp BL had been demonstrated with good results at Meppen. It remains to add that the two Dover 16 in and turret are still extant although declared obsolete in 1902.

‘Inflexible’ at Malta in her early days

Note About These Images

I need confirmation about my suspicion that the carriage shown above and to the right are proof mounts on a railway carnage and that  it was not an official railway gun.

Woolwich humor - comparing gun sizes