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An Armstrong gun was a uniquely designed type of rifled breech-loading field and heavy gun designed by Sir William Armstrong and manufactured in England beginning in 1855 by the Elswick Ordnance Company and the
Royal Arsenal The Royal Arsenal, Woolwich is an establishment on the south bank of the River Thames in Woolwich in south-east London, England, that was used for the manufacture of armaments and ammunition, proofing, and explosives research for the British ...
at Woolwich. Such guns involved a
built-up gun A built-up gun is artillery with a specially reinforced barrel. An inner tube of metal stretches within its elastic limit under the pressure of confined powder gases to transmit stress to outer cylinders that are under tension.Fairfield (1921) p. ...
construction system of a
wrought-iron Wrought iron is an iron alloy with a very low carbon content (less than 0.08%) in contrast to that of cast iron (2.1% to 4%). It is a semi-fused mass of iron with fibrous slag inclusions (up to 2% by weight), which give it a wood-like "grain" t ...
(later of mild steel) tube surrounded by a number of wrought-iron strengthening coils shrunk over the inner tube to keep it under compression.


The Armstrong rifled breechloading guns of the 1850s-1860s

In 1854, Armstrong approached the
Secretary of State for War The Secretary of State for War, commonly called War Secretary, was a secretary of state in the Government of the United Kingdom, which existed from 1794 to 1801 and from 1854 to 1964. The Secretary of State for War headed the War Office a ...
, proposing that he construct a rifled breech-loading 3-pounder gun for trial. Later increased in bore to 5-pounder, the design performed successfully with respect to both range and accuracy. Over the next three years he developed his system of construction and adapted it to guns of heavier calibre. Armstrong's system was adopted in 1858, initially for "special service in the field" and initially he only produced smaller
artillery Artillery is a class of heavy military ranged weapons that launch munitions far beyond the range and power of infantry firearms. Early artillery development focused on the ability to breach defensive walls and fortifications during sieges, ...
pieces, 6-pounder (2.5 in/64 mm) mountain or light field guns, 9-pounder (3 in/76 mm) guns for horse artillery, and 12-pounder (3 inches /76 mm) field guns. Armstrong did not consider his system suited to heavier guns but higher authorities had him develop a 20-pounder (3.75 inches /95 mm) field & naval gun, a 40-pounder () siege gun, and a 110-pounder (7 inches /180 mm) heavy gun. The
Royal Navy The Royal Navy (RN) is the United Kingdom's naval warfare force. Although warships were used by English and Scottish kings from the early medieval period, the first major maritime engagements were fought in the Hundred Years' War against ...
used all these guns and all except the 20-pounder saw service in New Zealand.


Armstrong breech-loading system

Armstrong's guns used a "built-up" construction, comprising a central "A" tube (initially of wrought iron, and from 1863 of mild steel toughened in oil) holding the bore over which were shrunk several wrought iron coils which kept the central tube under compression, a breech-piece, and a
trunnion A trunnion (from Old French "''trognon''", trunk) is a cylindrical protrusion used as a mounting or pivoting point. First associated with cannons, they are an important military development. Alternatively, a trunnion is a shaft that positions ...
ring. The guns' rifling was on the "polygroove" system; the bore of the gun had 38 grooves along its length with a twist of one turn per 38 calibres. The
cast iron Cast iron is a class of iron–carbon alloys with a carbon content more than 2%. Its usefulness derives from its relatively low melting temperature. The alloy constituents affect its color when fractured: white cast iron has carbide impuriti ...
shell, similar in shape to a Minié ball, had a thin lead coating which made it fractionally larger than the gun's bore and which engaged with the gun's
rifling In firearms, rifling is machining helical grooves into the internal (bore) surface of a gun's barrel for the purpose of exerting torque and thus imparting a spin to a projectile around its longitudinal axis during shooting to stabilize th ...
grooves to impart spin to the shell. This system had just been developed by
Martin von Wahrendorff Martin von Wahrendorff (1789 – 1861) was a Swedish diplomat and inventor. His father Anders von Wahrendorff was the owner of the gun foundry at Åker. Wahrendorff was Grand Master of Ceremonies at the Royal Court of Sweden from 1828 to ...
and
Giovanni Cavalli Lieutenant general Giovanni Cavalli (Novara, 23 July 1808 – Turin, 23 December 1879) was an Italian soldier, artillerist and inventor. He is credited with the creation of the first successful rifled breech loader gun. Biography He entered the ...
in Sweden. This spin, together with the elimination of
windage Windage is a term used in aerodynamics, firearms ballistics, and automobiles. Usage Aerodynamics Windage is a force created on an object by friction when there is relative movement between air and the object. Windage loss is the reduction in ...
as a result of the tight fit, enabled the gun to achieve greater range and accuracy than existing smoothbore muzzle-loaders with a smaller powder charge. On top of each gunpowder cartridge was a "lubricator" consisting of tallow and linseed oil between two tin plates, backed by a felt wad coated with beeswax and finally by
millboard Paperboard is a thick paper-based material. While there is no rigid differentiation between paper and paperboard, paperboard is generally thicker (usually over 0.30 mm, 0.012 in, or 12 points) than paper and has certain superior attribute ...
. The lubricator followed the shell down the bore, the lubricant was squeezed out between the tin plates and the wad behind it cleaned out any lead deposits left from the shell coating leaving the bore clean for the next round. An innovative feature which is more usually associated with 20th-century guns was what Armstrong called its "grip", which was essentially a squeeze bore; the 6 inches of the bore at the muzzle end was of slightly smaller diameter, which centered the shell before it left the barrel and at the same time slightly
swage Swaging () is a forging process in which the dimensions of an item are altered using dies into which the item is forced. Swaging is usually a cold working process, but also may be hot worked. The term swage may apply to the process (verb) or ...
d down its lead coating, reducing its diameter and slightly improving its ballistic qualities. The Armstrong breech loaders used a vertical sliding block, called a vent-piece, which had a conical copper-ringed plug on its front surface which sealed the firing chamber, to close the breech. To hold both block and plug tightly in place the guns used a hollow breech screw (hence the name "screw breech") behind the block, which the gunner rotated to tighten and seal the breech before firing. To load and fire the gun: * The breech screw was turned to loosen it * The vent-piece was raised * The shell was inserted through the hollow breech-screw and rammed home into the bore * The powder cartridge was inserted through the breech-screw into the chamber * A primer tube was inserted into the vent piece (only necessary for the 40-pounder and 110-pounder due to the size) * The vent-piece was lowered * The breech-screw was tightened * A friction tube with lanyard attached was inserted in the hole at the top of the vent-piece * The gunner pulled the
lanyard A lanyard is a cord, length of webbing, or strap that may serve any of various functions, which include a means of attachment, restraint, retrieval, and activation and deactivation. A lanyard is also a piece of rigging used to secure or lowe ...
which ignited a gunpowder charge in the vent tube, the flash passed through the vent in the vent-piece, assisted by the primer if present, into the powder chamber and ignited the gunpowder charge


Armstrong guns in action

The British used Armstrong guns extensively to great effect in the Second Opium War. As reported by the translator Robert Swinhoe, after the British attack on the Chinese fort at Pehtang:
Numbers of dead Chinese lay about the guns, some most fearfully lacerated. The wall afforded very little protection to the Tartar gunners, and it was astonishing how they managed to stand so long against the destructive fire that our Armstrongs poured on them; but I observed, in more instances than one, that the unfortunate creatures had been tied to the guns by the legs.
The Armstrong gun—mainly the 12 pounder—was used extensively in the 1863 conflict in New Zealand between British troops and Maori in the Waikato. A well preserved 12-pounder which was used in the
battle of Rangiriri The Battle of Rangiriri was a major engagement in the invasion of Waikato, which took place on 20–21 November 1863 during the New Zealand Wars. More than 1400 British troops defeated about 500 warriors of the Kingitanga (Māori King Movement), ...
is at the Te Awamutu museum. The barrel can traverse 6 degrees left or right without moving the gun carriage. The wheels are wooden with a 75 mm wide steel band. The wheel diameter is 1.7 m. The track width is 1.8 m. Barrel width at the muzzle is 140 mm. Such was the confidence of the army in the accuracy of the gun that at the battle of Hairini Ridge the artillery was fired over the heads of the advancing infantry as they stormed the ridge. The infantry took cover in a slight depression in the ground in front of the Maori trenches and then stormed the trenches when the shelling stopped. On July 4, 1868, Armstrong guns were used at the
Battle of Ueno The was a battle of the Boshin War, which occurred on July 4, 1868 (''Meiji 1, 15th day of the 5th month''), between the troops of the Shōgitai under Shibusawa Seiichirō and Amano Hachirō, and Imperial "Kangun" troops. Prelude Though the Sh ...
by forces supporting the Imperial government of Japan. Armstrong guns were used against British and Indian troops during the Second Anglo-Afghan War in the
Battle of Charasiab The Battle of Charasiab was fought on 6 October 1879 during the Second Anglo-Afghan War between British and Indian troops against Afghan regular forces and tribesmen. The battle The first phase of the Afghan War ended in May 1879 with the Trea ...
, in which Howard Hensman describes six being captured by a combined Anglo-Indian expedition under the command of Brigadier-General Baker.


Return to muzzle-loading guns

In 1863 an Ordnance Select committee met to consider the merits of muzzle-loading and breech-loading guns. In 1864, even before they had concluded their investigations, the Government stopped the manufacture of Armstrong breech-loaders. When the Committee finally reported, in August 1865, they announced that: Their report did admit that Armstrong's guns, while more expensive, were undoubtedly safer in that while it was not uncommon for cast iron muzzle-loaders to burst, not one Armstrong gun had ever done so. (Furthermore, gunners could clear a
hang fire Hang fire refers to an unexpected delay between the triggering of a firearm and the ignition of the propellant. This failure was common in firearm actions that relied on open primer pans, due to the poor or inconsistent quality of the powder. Mo ...
from the breech; when the
RML 17.72 inch gun The 100-ton gun (also known as the Armstrong 100-ton gun) was a rifled muzzle-loading (RML) gun made by Elswick Ordnance Company, the armaments division of the British manufacturing company Armstrong Whitworth, owned by William Armstrong. T ...
at
Napier of Magdala Battery Napier of Magdala Battery is a former coastal artillery artillery battery, battery on the south-western cliffs of the British Overseas Territories, British Overseas Territory of Gibraltar, overlooking the Bay of Gibraltar. It also overlooks Rosia ...
at Gibraltar hung fire, a gunner had to be lowered head-first down the bore to attach an extractor to the shell.) Despite a further report which remarked on the advantages of breech-loaders, cost dominated the proceedings and the Committee finally announced that "The balance of advantages is in favour of muzzle-loading field guns", and in 1865 Britain reverted from breech-loading ordnance to muzzle-loading. Tests conducted in 1859 with the Armstrong 40-pounder, and again in 1869 with the Armstrong rifled 100-pounder had demonstrated that neither rifled cannon was capable of penetrating 4 inches of armour, even at as little as 50 yards. This was crucial because Britain, as a maritime power, relied for its security on the ability of its naval ordnance to defeat any new armour-protected warships being developed by potential enemy powers. Armstrong developed an alternative horizontal sliding wedge version of his breechloader, for 40-pounder and 64-pounder guns, in an attempt to address the limitations of the screw breech, but the Government had already decided to return to muzzle-loading guns. To allow rifling to be used with muzzle-loaders, Armstrong proposed in 1866 a new system whereby the shells had studs on the outside, which aligned with grooves in the barrel of the
cannon A cannon is a large-caliber gun classified as a type of artillery, which usually launches a projectile using explosive chemical propellant. Gunpowder ("black powder") was the primary propellant before the invention of smokeless powder during ...
. This was adopted by the Government for the first generation of rifled muzzle-loaders, termed " RML", together with Armstrong's built-up wrought-iron construction method, which was considered sound.


Later Armstrong breechloaders

Armstrong returned to the manufacture of breechloaders in the 1880s, using an
interrupted thread Breech from Russian 122 mm M1910 howitzer, modified and combined with 105 mm H37 howitzer barrel An interrupted screw or interrupted thread is a mechanical device typically used in the breech of artillery guns. It is believed to have b ...
breech with its own "Armstrong cup" and later the de Bange methods of sealing the bore which relied upon the power of the gun's firing to effect the gas seal ("obturation") rather than the manual labour in the 1858 design. It was a major supplier of modern " BL" guns to the Royal Navy, British Army and the world export market until the 1920s. However, it is its earlier generations of " RBL" guns that are typically referred to as "Armstrong guns".


See also

* Rifled breech loader *
Disappearing gun A disappearing gun, a gun mounted on a ''disappearing carriage'', is an obsolete type of artillery which enabled a gun to hide from direct fire and observation. The overwhelming majority of carriage designs enabled the gun to rotate bac ...
for the ''Armstrong Disappearing Gun.''


Notes


References


Treatise on Ammunition. War Office, UK, 1877
*Alexander Lyman Holley
"A Treatise on Ordnance and Armor" published by D Van Nostrand, New York, 1865


Further reading

* Jack Beeching, ''The Chinese Opium Wars'' (1975),


External links

* Friedrich Engels,
"On Rifled Cannon"
articles from the New York ''Tribune'', April, May and June, 1860, reprinted in ''Military Affairs'' 21, no. 4 (Winter 1957) ed. Morton Borden, 193–198. {{VictorianEraBritishWeapons 1858 introductions Field artillery Coastal artillery Naval guns of the United Kingdom Scotswood Victorian-era weapons of the United Kingdom