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 at Woolwich. Such guns involved a built-up gun construction system of a wrought-iron (later of mild steel) tube surrounded by multiple wrought-iron strengthening coils shrunk over the inner tube to keep it under compression.
In 1854, Armstrong approached the Secretary of State for War, 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 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 (4.75 inches (121 mm)) siege gun, and a 110-pounder (7 inches /180 mm) heavy gun. The Royal Navy used all these guns and all except the 20-pounder saw service in New Zealand.
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, [1] a breech-piece, and a trunnion ring. [2] 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 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 grooves to impart spin to the shell. This system had just been developed by Martin von Wahrendorff and Giovanni Cavalli in Sweden. This spin, together with the elimination of windage 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. 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. [3]
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 swaged 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 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. [4]
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 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 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, in which Howard Hensman describes six being captured by a combined Anglo-Indian expedition under the command of Brigadier-General Baker. [5]
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:
The many-grooved system of rifling with its lead-coated projectiles and complicated breech-loading arrangements is far inferior for the general purpose of war to the muzzle-loading system and has the disadvantage of being more expensive in both original cost and ammunition. Muzzle-loading guns are far superior to breech-loaders in simplicity of construction and efficiency in this respect for active service; they can be loaded and worked with perfect ease and abundant rapidity.
Their report did admit that Armstrongs' 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 from the breech; when the RML 17.72 inch gun at Napier of Magdala Battery 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. [6]
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. 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.
Armstrong returned to the manufacture of breechloaders in the 1880s, using an interrupted thread 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".
A rifled breech loader (RBL) is an artillery piece which, unlike the smoothbore cannon and rifled muzzle loader (RML) which preceded it, has rifling in the barrel and is loaded from the breech at the rear of the gun.
This article explains terms used for the British Armed Forces' ordnance and also ammunition. The terms may have slightly different meanings in the military of other countries.
The Type 11 70 mm infantry mortar, was a muzzle-loading, rifled bore infantry mortar used by the Japanese. The Type 11 designation was given to this gun as it was accepted in the 11th year of Emperor Taishō's reign (1922). It was first used in 1922 and was the first mortar to be introduced by the Imperial Japanese Army. The mortar was later replaced by the Type 92 battalion gun.
The Armstrong RBL 7-inch gun, also known as the 110-pounder, was an early attempt to use William Armstrong's new and innovative rifled breechloading mechanism for heavy rifled guns.
A muzzle-loading rifle is a muzzle-loaded small arm or artillery piece that has a rifled barrel rather than a smoothbore. The term "rifled muzzle loader" typically is used to describe a type of artillery piece, although it is technically accurate for small arms as well. A shoulder arm is typically just called a "rifle", as almost all small arms were rifled by the time breechloading became prevalent. Muzzle and breechloading artillery served together for several decades, making a clear distinction more important. In the case of artillery, the abbreviation "RML" is often prefixed to the guns designation; a Rifled breech loader would be "RBL", or often just "BL", since smoothbore breechloading artillery is almost nonexistent. A muzzle loading weapon is loaded through the muzzle, or front of the barrel. This is the opposite of a breech-loading weapon or rifled breechloader (RBL), which is loaded from the breech-end of the barrel. The rifling grooves cut on the inside of the barrel cause the projectile to spin rapidly in flight, giving it greater stability and hence range and accuracy than smoothbore guns. Hand held rifles were well-developed by the 1740s. A popularly recognizable form of the "muzzleloader" is the Kentucky Rifle, which was actually developed in Pennsylvania. The American Longrifle evolved from the German "Jäger" rifle.
The Ordnance RML 2.5-inch mountain gun was a British rifled muzzle-loading mountain gun of the late 19th century designed to be broken down into four loads for carrying by man or mule. It was primarily used by the Indian Army.
The Armstrong Breech Loading 12 pounder 8 cwt, later known as RBL 12 pounder 8 cwt, was an early modern 3-inch rifled breech-loading field gun of 1859.
The BL 13.5 inch naval gun Mk I was Britain's first successful large breechloading naval gun, initially designed in the early 1880s and eventually deployed in the late 1880s. Mks I - IV were all of 30 calibres length and of similar construction and performance.
The RML 10-inch guns Mk I – Mk II were large rifled muzzle-loading guns designed for British battleships and monitors in the 1860s to 1880s. They were also fitted to the Bouncer and Ant-class flat-iron gunboats. They were also used for fixed coastal defences around the United Kingdom and around the British Empire until the early years of the 20th Century.
The RML 9-inch guns Mark I – Mark VI were large rifled muzzle-loading guns of the 1860s used as primary armament on smaller British ironclad battleships and secondary armament on larger battleships, and also ashore for coast defence.
A Blakely rifle is one of a series of rifled muzzle-loading cannon designed by British army officer Captain Theophilus Alexander Blakely. They were widely sold outside of the British army, and were best known for their use by the Confederate States of America during the American Civil War.
RML 16-inch 80-ton guns were large rifled muzzle-loading guns intended to give the largest British battleships parity with the large guns being mounted by Italian and French ships in the Mediterranean Sea in the 1870s.
The RML 12-inch 25-ton guns were large rifled muzzle-loading guns of mid-late 1800s used as primary armament on British ironclad turret battleships and coastal monitors, and also ashore for coast defence. They were the shorter and less powerful of the two 12-inch (305-mm) British RML guns, the other being the 35-ton gun.
The 68-pounder cannon was an artillery piece designed and used by the British Armed Forces in the mid-19th century. The cannon was a smoothbore muzzle-loading gun manufactured in several weights, the most common being 95 long cwt (4,800 kg), and fired projectiles of 68 lb (31 kg). Colonel William Dundas designed the 112 cwt version in 1841 and it was cast the following year. The most common variant, weighing 95 cwt, dates from 1846. It entered service with the Royal Artillery and the Royal Navy and saw active service with both arms during the Crimean War. Over 2,000 were made and it gained a reputation as the finest smoothbore cannon ever made.
The RML 7-inch guns were various designs of medium-sized rifled muzzle-loading guns used to arm small to medium-sized British warships in the late 19th century, and some were used ashore for coast defence.
The British RML 8-inch 9-ton guns Mark I – Mark III were medium rifled muzzle-loading guns used to arm smaller ironclad warships and coast defence batteries in the later 19th century.
The RML 8-inch howitzer was a British Rifled, Muzzle Loading (RML) Howitzer manufactured in England in the 19th century, which fired a projectile weighing approximately 180 pounds (82 kg). It was used in siege batteries and in fortifications.
The 3-inch Ordnance rifle, Model 1861 was a wrought iron muzzle-loading rifled cannon that was adopted by the United States Army in 1861 and widely used in field artillery units during the American Civil War. It fired a 9.5 lb (4.3 kg) projectile to a distance of 1,830 yd (1,670 m) at an elevation of 5°. The 3-inch rifle was not as effective in firing canister shot as the heavier 12-pounder Napoleon, but it proved to be highly accurate at longer ranges when firing shell or shrapnel. There was only one reported case of a 3-inch Ordnance rifle bursting in action. This was in stark contrast to the similarly-sized cast iron 10-pounder Parrott rifles which occasionally burst without warning, inflicting injury on the gun crews. The Confederate States of America lacked the technology to manufacture successful copies of the 3-inch Ordnance rifle. However, the Confederate States Army respected the weapons and employed those captured from Federal forces.
The RML 25-pounder gun was a British rifled muzzle-loading light siege gun and gun of position designed in 1871. It was intended to be an intermediate gun between the 16-pounder and 40-pounder Rifled Muzzle Loading guns. It was part of a series of guns designed after the British military reverted to rifled muzzle-loading artillery until a more satisfactory breech-loading system than that of the Armstrong guns was developed.
The RML 6.6 inch howitzer was a British Rifled, Muzzle Loading (RML) Howitzer manufactured in England in the 19th century, which fired a projectile weighing approximately 100 pounds (45 kg). It was used in siege batteries and in fortifications.
 | Wikimedia Commons has media related to Armstrong guns . |