100-ton gun
| Company type | Armaments manufacturer |
|---|---|
| Industry | Defense, Artillery manufacturing |
| Predecessor | Armstrong Whitworth (armaments branch) |
| Founder | William Armstrong, 1st Baron Armstrong |
| Headquarters | United Kingdom |
| Products | Rifled muzzle-loading guns, including the Armstrong 100-ton gun |
Template:More footnotes needed
The Armstrong 100-ton gun, commonly referred to simply as the 100-ton gun,[1] stands as the largest black powder cannon ever constructed. This British coastal defence weapon is a 17.72 inches ([convert: unknown unit])* Rifled muzzle loader (RML) manufactured by the Elswick Ordnance Company, the armaments branch of the British industrial firm Armstrong Whitworth, founded by William Armstrong, 1st Baron Armstrong. A total of fifteen of these guns were produced; eight were installed on two Italian battleships, while the remainder equipped British defensive positions in Malta and Gibraltar to counter the Italian naval threat.
Origins
Around 1870, the largest artillery piece produced by British manufacturers was the 320 mm rifled muzzle-loading (RML) gun, weighing 38 long tons (38.6 t). This gun fired an 818 lb projectile capable of penetrating approximately 16.3 inches of mild steel armor at a distance of 2,000 yards. Although this weapon met contemporary requirements, advancements in artillery technology progressed swiftly. French manufacturers soon developed a 420 mm gun weighing 76 tons, prompting the Royal Navy to request a gun weighing 81 tons.
Armstrong, the principal British artillery manufacturer, initiated development of an even larger cannon: an 18-inch gun, also referred to as the '100 ton' gun. Armstrong proposed this weapon to the Royal Navy; however, it was declined due to concerns over its excessive weight and cost.
General characteristics
At the time, the 100 ton gun was colossal. Its mass was comparable to that of the much later Iowa-class 406 mm (16.0 in)/50 caliber guns, despite having relatively short barrels. These were rifled muzzle-loading artillery pieces mounted rigidly. Operating each gun required a crew of 35 personnel, with 18 assigned specifically to ammunition handling.
Initial construction
The first version of the 100-ton gun featured a consistent bore diameter of 17 inches throughout its length. It measured approximately 32 feet 10.5 inches (L/23.5) in length. The barrel's exterior diameter was 77 inches near the breech, tapering to 29 inches at the muzzle. The bore length extended to 30 feet 6 inches, equivalent to 21.5 calibers. Rifling included 27 grooves, each one-eighth inch deep, with a progressive twist rate reaching L/45 at the muzzle. Instead of conventional studs, shells employed driving bands equipped with attached gas-checks. The overall weight of the gun was around 101.5 long tons (approximately 100 tons).
The construction involved an inner steel tube encased by multiple wrought iron coils. The inner tube itself was composed of two parts joined by a double ring—this segmentation resulted from manufacturing limitations preventing production as a single piece.
Loading mechanisms were hydraulically operated. To load, the barrel was lowered into a fixed position allowing insertion of the charge; then a ram head pushed the projectile up the bore until it seated against the charge. Following firing, the barrel returned to this position for cleaning: a ram with a sponge head was inserted and activated to release a strong water jet that cleared residual embers from the barrel interior. Once cleaning was complete and the ram withdrawn, new charges and projectiles were brought forward and positioned before the barrel for subsequent loading. All these steps were controlled manually by an operator using levers.
Firing could be triggered mechanically or electrically, with aiming facilitated through an optical sighting system.
The crew could achieve a firing rate of one round every six minutes. The muzzle velocity reached approximately 472 m/s, with maximum elevation limited to 10°30'. At full charge (around 204 kg) and maximum elevation, projectiles could travel up to roughly 5,990 meters. At this range, they were still capable of penetrating about 394 mm of steel armor (the type—mild or hardened—is unspecified).
Mount weights included: mobile mounts equipped with eighteen wheels at approximately 20,680 kg; platform mounts weighing around 24,118 kg; and bases about 2,032 kg. The platform was inclined at four degrees to help absorb recoil forces. Hydraulic systems powered chains that allowed traversing across a 150-degree arc on platform mounts, while another hydraulic mechanism controlled elevation adjustments.
Re-chambering
Following evaluations conducted in Italy, the initial gun was sent back to the manufacturing facility to be modified with a caliber of 17.75 in (451 mm) and a powder chamber diameter of 19.75 in (502 mm). This process, known as chambering, was a recent advancement that increased the charge chamber volume by approximately 35%. Theoretically, expanding the chamber size permitted a larger propellant charge without increasing the maximum pressure. However, enlarging the chamber bore reduced the barrel's structural integrity, necessitating reinforcement near the front section of the chamber while maintaining the original weight. Additionally, shallower polygonal rifling was introduced as part of these enhancements. All subsequent guns were manufactured incorporating these modifications from the outset.
Ammunition
This artillery piece represented a second-generation rifled muzzle-loading (RML) gun featuring polygroove rifling and exclusively firing studless projectiles equipped with automatic gas-checks to ensure rotation.
Three types of projectiles were utilized, each weighing 2,000 pounds (910 kg) and measuring 17.7 inches (450 mm) in diameter:
- Armor-piercing (AP) Palliser rounds, 44 inches (1.12 m) in length, with a steel nose section capable of penetrating 21 in (0.53 m) of steel armor at 2,000 yards (530 mm at 1,800 m), containing a 32-pound (14.5 kg) internal explosive charge.
- High explosive (HE) Common shells, measuring 48+1⁄2 inches (1.23 m) in length, featuring thinner walls and loaded with a 78-pound (35 kg) high-explosive charge.
- Shrapnel shells: 45 inches (1.1 m) long, containing only a 5 pounds (2.3 kg) high-explosive charge but packed with 920 bullets each weighing approximately 4 ounces (110 g).
The firing charges were polygonal in shape, with maximum dimensions of 399 x 368 mm. These charges consisted of 1 cwt (51 kg (112 lb)) of 'Large Black Prism' propellant; typically, four or five charges were required to fire each shell at full power. The recoil distance measured 1.75 m (5 ft 9 in), as two hydraulic pistons located at the rear portion of the platform absorbed the residual energy.
The Italian order
Following Italy’s reunification, the Regia Marina embarked on an ambitious program aimed at deploying some of the most formidable battleships available during that era. The initial vessels in this initiative were from the Duilio-class, equipped with 380 mm artillery pieces. Although these guns were already highly potent, Italian naval commanders sought even greater firepower after Britain commenced construction of HMS Inflexible, armed with 406 mm (16.0 in) guns, in February 1874. To maintain superiority in battleship armament design, Italy requested artillery surpassing these specifications.
On 21 July 1874, Armstrong formalized an agreement with Italy to supply eight 100-ton guns—sufficient to outfit both Duilio and her sister ship Dandolo.
Transport
The commissioning of the 100-ton gun was intimately connected with the erection of the Swing Bridge spanning the River Tyne in Newcastle upon Tyne. This hydraulic swing bridge, also constructed by Armstrong, was the largest of its kind globally at that period. It was inaugurated on 17 July 1876 by the Italian Navy steamer Europa, which arrived specifically to pick up the first 100-ton gun.
In La Spezia, a dedicated 160-ton crane was installed at the naval arsenal to facilitate handling of the massive gun. This steam-powered hydraulic crane, designed by George Wightwick Rendel, represented Italy’s first of its kind.
Tests at La Spezia
The Italian Navy conducted firing trials of the 100-ton gun at Muggiano, close to La Spezia. The gun was mounted on an iron pontoon measuring 26 by 16 m, which extended approximately 1 m above the water surface. This pontoon was moored in a basin near shore, and elevation adjustments were hydraulically controlled via a steam engine. The design of the pontoon allowed rotation of the gun in lieu of a traditional turret.
The installation was overseen by George Rendel and Captain Noble, both partners in Armstrong’s firm. Noble was recognized as an authority on cannon gas pressures. Other British observers included Col. Younghusband from Woolwich Arsenal and Col. Brakenbury representing the London Times.
Initial firing tests took place on 20, 22, and 23 October 1876. Velocity measurements were successfully recorded on the third day; using a 330 pounds (150 kg) charge propelling a 2,000 pounds (910 kg) projectile, a velocity of 1,446 feet per second (441 m/s) was achieved.
These trials against armored targets garnered international interest. The targets simulated ship hulls and were positioned on embankments within a ravine. The first target consisted of two vertically stacked Creusot steel plates, each 22 inches (56 cm) thick and measuring 11 feet 11 inches (3.63 m) long by 4 feet 8 inches (1.42 m) wide, backed by two layers of teak totaling 29 inches (74 cm) in thickness. Behind this assembly lay a 1.5 inches (3.8 cm) iron skin followed by structural frames mimicking those found on ships. These steel plates were noted for their softness, intended to provide ductility that would prevent fracturing.
The second target shared similar characteristics but featured wrought iron front plates supplied by Sheffield’s Cammell above and Marrell below. The third target maintained identical dimensions; however, its upper half incorporated two wrought iron plates from Cammell measuring 12 and 10 inches thick separated by 14 inches of timber. The lower half combined a 14-inch chilled cast iron plate at the rear with an 8-inch wrought iron plate in front. The fourth target resembled the third but utilized Marrell plates with timber interposed between wrought and chilled iron layers. All four targets had an aggregate thickness of approximately 4 feet 4 inches (1.32 m).
Positioned roughly 110 m from these targets, the raft-mounted 100-ton gun operated alongside additional artillery including an RML 11-inch 23-ton gun and two RML 10-inch 18-ton guns stationed about 80 m from their respective targets to ensure comparable range. The smaller guns were arranged to be moved laterally to clear firing paths for the larger weapon.
On 25 October, firing with the 10-inch gun targeted the upper section of the steel plate target. The projectile penetrated only about 10 inches (25 cm) into the first plate; shortly thereafter, audible vibrations emerged as cracks propagated from the impact point. Both Cammell and Marrell wrought iron plates withstood this fire from the 10-inch gun. Subsequent firings by both the 10- and 11-inch guns breached the steel target. That day concluded with the 100-ton gun discharging towards open sea. On the following day, it fired upon an undamaged Creusot plate, completely demolishing it; however, despite breaking apart, the shot did not fully penetrate.
Experts determined that steel was inadequate for armor purposes but were intrigued by crack formations caused by lighter projectiles. In ensuing days, firings against wrought iron targets showed that while these plates remained intact without fragmentation, projectiles passed through them retaining velocities near 600 feet per second (180 m/s), leaving substantial tears in their structure—reigniting debate over iron versus steel armor effectiveness. By mid-November 1876, Nathaniel Barnsby, Director of Naval Construction for the Royal Navy, planned to visit La Spezia to evaluate these findings and assess steel’s suitability.
A comprehensive illustrated report documented these trials in detail. Between 20 October and 8 November 1876, the 100-ton gun discharged a total of thirty-nine rounds. Most charges utilized English government-produced Waltham Abbey gunpowder composed of one-and-a-half inch cubes; some firings employed less potent Fossano powder. The highest recorded pressure reached approximately 20.8 tons per square inch (3,170 atm) with a 330 pounds (150 kg) charge producing a muzzle velocity of about 443 m/s.
Pressure readings exhibited considerable variability; intriguingly, certain higher charges generated lower peak pressures. Consequently, Armstrong representatives recommended capping charges at around 145 kg (300 lb), yielding velocities near 434 m/s—exceeding contractual expectations of 423 m/s at a pressure of roughly 2,800 atm.
Evaluation of the Chambered Gun
Following the production of the initial chambered guns, one was subjected to testing in La Spezia during March and April 1878. A total of 85 rounds were fired during this evaluation. The objectives were threefold: to gather ballistic performance data using British gunpowder and compare it with that of the original gun; to assess the Italian Fossano gunpowder against the English P2 variant; and to identify the optimal cartridge design along with the most effective ignition method.
The original gun, firing a projectile weighing 2,000 pounds (910 kg), achieved a velocity of 1,424 feet per second (434 m/s) at a pressure of 18.3 tons per square inch with appropriate charges. In contrast, the chambered gun reached a velocity of 1,585 feet per second (483 m/s) at a slightly lower pressure of 17 tons per square inch, indicating that chambering enhanced the gun’s energy output by approximately 25%.
Regarding propellants, Fossano gunpowder demonstrated notable efficiency. Three test shots utilized an average charge of 433.4 pounds (196.6 kg) of English powder and 492.2 pounds (223.3 kg) of Fossano powder. On average, Fossano powder increased the gun’s energy by roughly three percent while decreasing pressure by about 4 tons per square inch. Additionally, while English powder ignited best at the center of the charge, Fossano powder showed no significant disadvantage when ignited at the charge’s end.
Incident
During firing tests conducted on 5 March 1880, one of Duilio's guns developed a crack while operating at maximum charge. Following recommendations from the British Army, it was officially determined that the maximum safe charge should be limited to 204 kg (450 lb), rather than the previously used 255 kg (562 lb).
British Reaction
The British authorities were alarmed upon learning about the Italian contract, especially considering their responsibility for defending the naval base at Malta. Since the opening of the Suez Canal in 1869, Malta had become Britain's key Mediterranean stronghold. Although its defenses included 320 mm (13 in) artillery pieces, these were insufficient against potential attacks from ships like those of the Duilio class. This concern was heightened by Francesco Crispi, a principal figure in Italian unification, who had referred to Malta as "Italia irredenta" ("Unredeemed Italy").
The British feared that heavily armored vessels such as Duilio and Dandolo could engage Malta’s coastal batteries from beyond their effective firing range, systematically neutralizing them. Despite these worries, no immediate actions were taken by London until after Duilio was launched in May 1876. The Royal Navy subsequently requested proposals from domestic arms manufacturers for artillery capable of penetrating 36 inches (900 mm) of steel armor at a distance of 1000 yards (900 m). The responses included designs for massive guns weighing 163, 193, and 224 tons.
In December 1877, Simmons, who oversaw Malta’s defenses, was summoned to London for discussions. He requested four guns comparable to those on Duilio, capable of engaging targets at approximately 3,000 yd (2,700 m). Given the urgency, it was decided to forego developing larger guns and instead procure identical weapons to those mounted on Duilio, since shore batteries equipped with guns matching a ship’s caliber generally maintain an advantage over that vessel. Four guns were ordered in March 1878 with production commencing in August; meanwhile, sea trials for Duilio had been underway since 1877.
Upon learning about these large-caliber guns, commanders at Gibraltar also requested similar armaments and successfully acquired two of the four guns initially intended for Malta.
Service in Malta
The cargo ship HMS Stanley, specially modified for this purpose, transported the two guns destined for Malta. One was installed at Cambridge Battery, completed in 1886, while the other was positioned at Rinella Battery, finished in 1884. The gun for Cambridge arrived on 16 September 1882 but was only mounted on 20 February 1884. Meanwhile, Rinella's gun was delivered on 31 July 1883 and mounted by 12 January 1884. By then, the Duilio-class battleships had been in service for approximately seven years.
Extensive work was required to render these weapons operational, resulting in no firing tests until 1885. The initial ammunition shipment included a variety of types, such as 50 armour-piercing and 50 high-explosive shells. Shrapnel rounds were fired once but not replenished, as they were deemed less effective. Operations ceased between 1887 and 1888 to allow for hydraulic system modifications; nonetheless, the guns were regarded as reliable and remained in service for over two decades.
The guns’ service history was uneventful since no Italian battleships posed a threat to Malta after their installation. These guns were retired in 1906, alongside the last remaining gun at Gibraltar, having fired their final rounds a few years earlier in 1903 or 1904.
During First World War, the Maltese guns were reportedly prepared for action when SMS Goeben was detected nearby. Despite their considerable size—approximately 100 t (98 long tons; 110 short tons)—the guns were outmatched by contemporary artillery. Their limited range and slow firing rate could not compete with modern 280–305 mm (11.0–12.0 in) naval guns, which boasted ranges exceeding 15–20 km (9.3–12.4 mi) and could fire every 30 seconds. Consequently, Goeben would have easily overpowered the Maltese defenses.
Service in Gibraltar
Gibraltar’s first battery designed for these guns was Napier of Magdala, located at Rosia Bay. The second battery, named Victoria Battery, was situated roughly one kilometre to the north. Construction commenced in December 1878; Napier was completed by 1883 and Victoria by 1884.
HMS Stanley also delivered Gibraltar’s pair of guns. The initial piece arrived on 19 December 1882, followed by the second on 14 March 1883. Both guns were mounted by July and September of 1883 respectively.
Although firings began in 1884, full operational status was delayed until 1889 due to issues with the hydraulic systems. During testing, the barrel of the Napier gun cracked because the crew had fired at an excessive rate—one shot every two and a half minutes—putting undue stress on the weapon. This damaged gun could not be effectively repaired and was repurposed as a foundation for a structure. The Victoria Battery’s gun was relocated to Napier, which military authorities considered a more strategic position.
The surviving guns
The two remaining guns at Napier of Magdala Battery and Fort Rinella remain intact and accessible to visitors. Due to their high demolition costs, they were initially abandoned but later restored for exhibition purposes. Fort Rinella is managed by Fondazzjoni Wirt Artna - the Malta Heritage Trust. The pink coloration seen on the Fort Rinella gun is a recent addition; originally, these guns were left unpainted.
Gallery
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Projectile measuring 17.72 in (45.0 cm) -
Duilio's twin turret -
RML gun of 17.72 in (45.0 cm) caliber, located in Gibraltar -
RML artillery piece, 17.72 in (45.0 cm), Gibraltar -
Video showing loading and firing of the model
Citations
References
- "Italian Naval Ordnance". The United States Army and Navy Journal and Gazette. Vol. XV. 3 November 1877.
- Brassey, Thomas (1882). The British Navy. Vol. II. Longmans, Green and Co. London.
- Caruana, Joseph, The British 100 t guns, Storia militare magazine n.22, July 1995.
- "Several articles". The Engineer. XLII. The Engineer, London: 269. 1876.
- Handbook for RML 17.72 inch gun, 1887, HMSO publications.
- Hughes, Q., Malta: A Guide to the Fortifications and Britain in the Mediterranean: the defense of her Naval stations
- "The Great Armstrong Gun and Swing Bridge at Newcastle". The Illustrated London News. 29 July 1876.
- "TBD". The Journal of the Royal Artillery. 126–127: 40. 1999.
- Mackinlay, George (1887). Text Book of Gunnery. Her Majesty's Stationery Office.
- Ordnance College (1902). Text Book of Gunnery. London: His Majesty's Stationery Office. Retrieved 12 July 2012.
- Possner, Roger (2009). The Rise of Militarism in the Progressive Era, 1900-1914. McFarland. p. 218. ISBN 9780786454112.
- "Progress of Artillery". Scientific American: Supplement. 6: 2222-2223. 1878.
- Di Rimieni, A. (1876). "Gli Esperimenti del Cannone Margherita alla Spezia". L'illustrazione italiana. No. 54. Fratelli Treves, Milano. pp. 363, 374, 407, 430.
- Schull, Herman W. (1901). "Spanish Ordnance in the Defense of Havana". Journal of the United States Artillery. 15 (2): 129–146.
External links
- Commons category:RML 17.72 inch gun
- NJM Campbell, BRITISH SUPER-HEAVY GUNS
- Footage of 100-ton gun firing at Fort Rinella, Malta on YouTube
- Image of 100-ton gun automatic gas-check on BBC website (retrieved 2016-09-03)
- Animation depicting the firing cycle
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