RBL 7-inch Armstrong gun
| Company type | Artillery piece |
|---|---|
| Industry | Military artillery |
| Founded | 1861 |
| Founder | William Armstrong |
Area served | United Kingdom, British military forces |
| Products | Rifled breechloading guns |
The Armstrong RBL 7-inch gun, frequently referred to as the 110-pounder,[1] represented a large-caliber Armstrong gun and was among the early rifled breechloading artillery pieces.
William Armstrong's pioneering design combined rifling with a built-up gun structure and breechloading technology, which had been effective in smaller artillery pieces. However, when scaled up to a seven-inch bore firing a projectile weighing approximately 110 pounds, it became evident that the pressure generated by the propellant charge exceeded the capacity of his breechloading mechanism to safely contain it.
Description
The Armstrong "screw" breech operated with a substantial block that slid vertically into a slot behind the chamber, secured by a large hollow screw manually tightened against it after loading. A metal cup affixed to the front of this block, combined with the pressure from the screw behind, provided obturation, effectively sealing the breech to prevent gas leakage during firing. This sliding-block, referred to as the "vent-piece," allowed insertion of the vent tube through it to ignite the charge; in contemporary terminology, it functioned as a vertical sliding-block.
Loading involved raising the vent-piece, inserting the shell through the hollow screw and ramming it into the bore, followed by placing the powder cartridge through the screw into the chamber. After lowering the vent-piece and tightening the screw, a tube was inserted atop the vent-piece to fire the weapon.
The shells featured a thin lead coating that made them slightly larger than the bore diameter, engaging with rifling grooves to impart spin. This spin, coupled with an elimination of windage due to the close fit, enhanced both range and accuracy compared to smoothbore muzzle-loaders using smaller powder charges.
Each powder cartridge was topped with a "lubricator" composed of tallow and linseed oil sandwiched between two tin plates, followed by a beeswax-coated felt wad and finished with millboard. As the lubricator traveled down the barrel behind the shell, lubricant was expelled between the tin plates while the wad removed lead residue from the shell’s coating, ensuring a clean bore for subsequent shots.
History
This breech-loading system had already demonstrated success in smaller artillery pieces like the RBL 12 pounder 8 cwt field gun. Despite Armstrong’s reservations about its suitability for heavier guns, British authorities insisted on adopting it for larger calibers:
The original model weighed 72 cwt (8,064 lb), but it was the heavier 82 cwt (9,184 lb) variant—with an added strengthening coil around the powder chamber—that entered service first in 1861. Designed to replace smoothbore muzzle-loading 68-pounder guns, this represented Britain’s initial modern rifled breech-loading naval artillery. The lighter 72 cwt version was eventually introduced in 1863 exclusively for land deployment.
During extensive hearings in 1862–63, Britain’s Select Committee on Ordnance evaluated Armstrong breechloaders against other artillery systems and concluded:
The limited maximum propellant charge—12 pounds initially, later reduced to 11 lb for the 82 cwt model and 10 lb for the 72 cwt—restricted muzzle velocity sufficiently to prevent effective penetration of ironclad warship armor:
Additional criticism targeted operational drawbacks such as the manual effort required to lift the heavy (136 lb) vent-piece before reloading, which hampered combat efficiency. Moreover, obturation depended entirely on how firmly gunners tightened the breech screw after loading:
Given these inherent limitations in Armstrong’s breech design and absence of superior alternatives at that time, production of the 110-pounder ceased in 1864. Subsequently, Britain reverted to muzzle-loading heavy artillery. The remaining guns were reassigned as fortress artillery and remained in service throughout much of Queen Victoria’s reign.
Following abandonment of Armstrong’s breech-loaders, Britain launched an extensive program producing rifled muzzle-loaders (RMLs) for naval use. The Armstrong 110-pounder was succeeded by various RML models of 7- and 8-inch calibers. Guns under construction as 7-inch Armstrong breech-loaders were completed instead as RML 64-pounder muzzle-loaders. Nevertheless, Armstrong’s construction technique—featuring a wrought-iron "A" tube reinforced by wrought-iron coils—was deemed robust and adopted for early rifled muzzle-loaders introduced in the mid-1860s.
When Britain resumed use of breech-loading artillery in 1880, it employed obturation systems such as Elswick’s cup and France’s De Bange design that relied on firing pressure itself to seal the breech rather than manual screwing effort.
Use in action
Royal Navy vessels deployed this artillery extensively against coastal defenses during the Bombardment of Kagoshima and Bombardment of Shimonoseki in 1863 and 1864. Two separate accounts describe the same episode aboard HMS Euryalus during the Kagoshima bombardment in August 1863:
While these guns performed well when correctly managed, they were considered challenging and potentially hazardous under combat pressures.
In the New Zealand Wars, this artillery was employed during the shelling of Maori defenses at Gate Pa on 29 April 1864.[2] Despite enduring one of the most intense bombardments of the conflict, Maori defenders utilized anti-artillery bunkers effectively and succeeded in repelling British forces while inflicting significant casualties.[3]
Ammunition
Surviving examples
- An 82cwt cannon located at Victoria Barracks, Sydney
- An 82cwt cannon situated in Saint Helier, Jersey
- A 72cwt cannon displayed at Fort Nelson, Portsmouth, UK.[4] This piece is equipped with a reproduction breech and carriage.[4]
- Preserved at Fort Henry, Ontario, Canada
- A 72 cwt cannon located at Quebec Citadel, Canada
- A 72 cwt cannon positioned at Fort No. 1, Lévis, Quebec
See also
Notes and references
- ↑ Cite error: Invalid
<ref>tag; no text was provided for refs namednameorigin - ↑ "Chapter 42: Gate Pa and Te Ranga". NZETC.
- ↑ "Gate Pā, Tauranga".
- ↑ 4.0 4.1 Impey, Edward, ed. (2022). Treasures of the Royal Armouries A Panoply of Arms. Royal Armouries Museum. p. 246. ISBN 9781913013400.
Bibliography
- Treatise on Ammunition. War Office, UK, 1877Template:Fix/category[permanent dead link]
- Treatise on the construction and manufacture of ordnance in the British service. War Office, UK, 1877
- Treatise on the Construction and Manufacture of Ordnance in the British Service. War Office, UK, 1879
- Text Book of Gunnery, 1887. LONDON : PRINTED FOR HIS MAJESTY'S STATIONERY OFFICE, BY HARRISON AND SONS, ST. MARTIN'S LANE Archived 4 December 2012 at archive.today
- Text Book of Gunnery, 1902. LONDON : PRINTED FOR HIS MAJESTY'S STATIONERY OFFICE, BY HARRISON AND SONS, ST. MARTIN'S LANE Archived 12 July 2012 at archive.today
- Alexander Lyman Holley, "A Treatise on Ordnance and Armor" published by D Van Nostrand, New York, 1865
- Lieutenant-Colonel C H Owen R.A., "The principles and practice of modern artillery". Second edition, published by John Murray, London, 1873
- W.L. Ruffell, "The Armstrong Gun Part 4: Other Armstrong Equipments in New Zealand" – use ashore in New Zealand Wars
- W.L. Ruffell, "The Armstrong Gun Part 5: British revert to Muzzle Loading"
External links
- 1892 Manual for the 7-inch R.B.L. guns weighing 72 cwt and 82 cwt, mounted on Moncrieff and sliding carriages, Land Service available at the State Library of Victoria
- Overview of the 7-inch R.B.L. hosted on the Victorian Forts website
- Illustration of the 82 cwt gun mounted on a sliding garrison carriage provided by the Victorian Forts website
- Illustration of the 82 cwt gun positioned on a casemate platform from the Victorian Forts website
- Image collection on Flickr
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