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A rifled breech loader (RBL) is an
artillery Artillery consists of ranged weapons that launch Ammunition, 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, and l ...
piece which, unlike the
smoothbore A smoothbore weapon is one that has a barrel without rifling. Smoothbores range from handheld firearms to powerful tank guns and large artillery mortars. Some examples of smoothbore weapons are muskets, blunderbusses, and flintlock pistols. ...
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 th ...
and rifled muzzle loader which preceded it, has
rifling Rifling is the term for helical grooves machined into the internal surface of a firearms's barrel for imparting a spin to a projectile to improve its aerodynamic stability and accuracy. It is also the term (as a verb) for creating such groov ...
in the barrel and is loaded from the breech at the rear of the gun. The spin imparted by the gun's
rifling Rifling is the term for helical grooves machined into the internal surface of a firearms's barrel for imparting a spin to a projectile to improve its aerodynamic stability and accuracy. It is also the term (as a verb) for creating such groov ...
gives projectiles directional stability and increased range. Loading from the rear of the gun leaves the crew less exposed to enemy fire, allows smaller gun emplacements or turrets, and allows a faster rate of fire. These rapidly improving breech systems and the powerful new guns they facilitated led to an
arms race An arms race occurs when two or more groups compete in military superiority. It consists of a competition between two or more State (polity), states to have superior armed forces, concerning production of weapons, the growth of a military, and ...
in
fortification A fortification (also called a fort, fortress, fastness, or stronghold) is a military construction designed for the defense of territories in warfare, and is used to establish rule in a region during peacetime. The term is derived from Lati ...
and
ironclad An ironclad was a steam engine, steam-propelled warship protected by iron armour, steel or iron armor constructed from 1859 to the early 1890s. The ironclad was developed as a result of the vulnerability of wooden warships to explosive or ince ...
warship design that led to the
battleship A battleship is a large, heavily naval armour, armored warship with a main battery consisting of large naval gun, guns, designed to serve as a capital ship. From their advent in the late 1880s, battleships were among the largest and most form ...
class of HMS ''Dreadnought'' and continued until the start of
World War I World War I or the First World War (28 July 1914 – 11 November 1918), also known as the Great War, was a World war, global conflict between two coalitions: the Allies of World War I, Allies (or Entente) and the Central Powers. Fighting to ...
.


Overview

The major problem to be solved with breechloading artillery was
obturation Obturation is the necessary barrel blockage or fit in a firearm or airgun created by a deformed soft projectile. A bullet or pellet made of soft material and often with a concave base will flare under the heat and pressure of firing, filling the ...
: the sealing of the breech after firing to ensure that none of the gases generated by the
burning Combustion, or burning, is a high-temperature exothermic redox chemical reaction between a fuel (the reductant) and an oxidant, usually atmospheric oxygen, that produces oxidized, often gaseous products, in a mixture termed as smoke. Combust ...
of the
propellant A propellant (or propellent) is a mass that is expelled or expanded in such a way as to create a thrust or another motive force in accordance with Newton's third law of motion, and "propel" a vehicle, projectile, or fluid payload. In vehicle ...
(initially
gunpowder Gunpowder, also commonly known as black powder to distinguish it from modern smokeless powder, is the earliest known chemical explosive. It consists of a mixture of sulfur, charcoal (which is mostly carbon), and potassium nitrate, potassium ni ...
) escaped rearwards through the breech. This was both a safety issue and one of gun performance – all the propellant gas was needed to accelerate the projectile along the barrel. The second problem was speed of operation – how to close the breech before firing and open it after firing as quickly as possible consistent with safety. Two solutions were developed more or less in parallel, the "screw breech" block and "sliding wedge" or "sliding block". At the time of development of the first modern breechloaders in the mid-19th century, gunpowder propellant charges for artillery were typically loaded in cloth bags, which combusted totally on firing. Hence, unlike with a metal rifle cartridge, the breech mechanism itself somehow needed to provide obturation. The early "screw" mechanisms for sealing the breech consisted of threaded blocks which were screwed tightly into the breech after loading, but the threads themselves were insufficient to provide a gas-tight seal. This was further complicated by the need to screw and unscrew the breech as quickly as possible; this was met by the " interrupted thread" breech block, where the block circumference was alternately threaded and left unthreaded at a slightly smaller diameter to allow the whole block to be fully inserted and rotated a fraction to lock it. Hence if the block circumference was divided into two sets of threads and gaps, the block only needed to be rotated ¼ turn to lock it instead of several turns. The tradeoff was that only ½ the block's circumference was threaded, reducing the security accordingly. The other possibility of sealing the breech was to enclose the propellant charge in a metal cartridge case which expanded on firing and hence sealed the breech, leaving the breech-block merely needing to lock the cartridge case in place. This was more easily accomplished by sliding the block in behind the cartridge case through a vertical or horizontal slot cut through the rear of the breech : the "sliding wedge" or "sliding block" breech.


History


Early breechloaders

The very first
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 th ...
s of the
Middle Ages In the history of Europe, the Middle Ages or medieval period lasted approximately from the 5th to the late 15th centuries, similarly to the post-classical period of global history. It began with the fall of the Western Roman Empire and ...
were breech loaded, with
gunpowder Gunpowder, also commonly known as black powder to distinguish it from modern smokeless powder, is the earliest known chemical explosive. It consists of a mixture of sulfur, charcoal (which is mostly carbon), and potassium nitrate, potassium ni ...
and shot contained in pots dropped at the back of the barrel, but the poor seals made them dangerous, and they wore quickly and could not be scaled to larger weapons. Until the 19th century, mainly muzzle-loaders were used. In 1837, Martin von Wahrendorff patented a design for a breech-loader with a cylindrical breech plug secured by a horizontal wedge; it was adopted by Sweden in 1854. Independently, Giovanni Cavalli first proposed a breech-loader gun in 1832 to the Sardinian Army, and first tested such a gun in 1845.


Armstrong screw breech

Advances in metallurgy in the industrial era allowed for the construction of rifled breech-loading guns that could fire at a much greater
muzzle velocity Muzzle velocity is the speed of a projectile (bullet, pellet, slug, ball/ shots or shell) with respect to the muzzle at the moment it leaves the end of a gun's barrel (i.e. the muzzle). Firearm muzzle velocities range from approximately t ...
. After the British artillery was shown up in the
Crimean War The Crimean War was fought between the Russian Empire and an alliance of the Ottoman Empire, the Second French Empire, the United Kingdom of Great Britain and Ireland, and the Kingdom of Sardinia (1720–1861), Kingdom of Sardinia-Piedmont fro ...
as having barely changed since the
Napoleonic Wars {{Infobox military conflict , conflict = Napoleonic Wars , partof = the French Revolutionary and Napoleonic Wars , image = Napoleonic Wars (revision).jpg , caption = Left to right, top to bottom:Battl ...
the industrialist William Armstrong was awarded a contract by the government to design a new piece of artillery. Production started in 1855 at 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, proof test, proofing, and explosives research for ...
at
Woolwich Woolwich () is a town in South London, southeast London, England, within the Royal Borough of Greenwich. The district's location on the River Thames led to its status as an important naval, military and industrial area; a role that was mainta ...
. His "Armstrong screw" breech involved loading the shell and gunpowder propellant charge in a cloth bag through the hollow breech screw, lowering a heavy block into a slot behind the powder chamber and screwing the breech screw tightly against the block to lock it in place. A degree of
obturation Obturation is the necessary barrel blockage or fit in a firearm or airgun created by a deformed soft projectile. A bullet or pellet made of soft material and often with a concave base will flare under the heat and pressure of firing, filling the ...
was achieved via a cup on the face of the block being forced into a recessed ring on the chamber face. The system was in effect a vertical sliding block such as later used by
Krupp Friedrich Krupp AG Hoesch-Krupp (formerly Fried. Krupp AG and Friedrich Krupp GmbH), trade name, trading as Krupp, was the largest company in Europe at the beginning of the 20th century as well as Germany's premier weapons manufacturer dur ...
in both horizontal and vertical form, with the crucial difference that Armstrong failed to make the progression to loading the powder charge in a metal cartridge, with the result that complete obturation was impossible. Whatever obturation that was achieved relied on manual labour rather than the power of the gun's firing, and was hence both uncertain, based on an unsound principle and unsuited to large guns. Armstrong screw-breech guns were initially adopted by the
British Army The British Army is the principal Army, land warfare force of the United Kingdom. the British Army comprises 73,847 regular full-time personnel, 4,127 Brigade of Gurkhas, Gurkhas, 25,742 Army Reserve (United Kingdom), volunteer reserve perso ...
and
Royal Navy The Royal Navy (RN) is the naval warfare force of the United Kingdom. It is a component of His Majesty's Naval Service, and its officers hold their commissions from the King of the United Kingdom, King. Although warships were used by Kingdom ...
, but concerns about limited armour penetration of the shells due to limited maximum velocity, safety concerns with the breech blocks blowing out of guns, and higher skill levels demanded of gunners led the British Government to revert to rifled muzzle-loaders from 1865 to 1880, when Britain finally deployed reliable screw breech mechanisms. The Imperial Japanese Army used Armstrong cannon during the
Boshin War The , sometimes known as the Japanese Revolution or Japanese Civil War, was a civil war in Japan fought from 1868 to 1869 between forces of the ruling Tokugawa shogunate and a coalition seeking to seize political power in the name of the Impe ...
to devastate the Aizu castle town and force its inhabitants to surrender quickly, and British Armstrong light field guns proved deadly against Chinese forces in the
Second Opium War The Second Opium War (), also known as the Second Anglo-Chinese War or ''Arrow'' War, was fought between the United Kingdom, France, Russia, and the United States against the Qing dynasty of China between 1856 and 1860. It was the second major ...
. However, the British Army and Navy preferred to revert to muzzle-loaders until larger high-powered breech-loaders with secure obturation systems that were relatively simple to operate were developed.


Broadwell ring

American engineer Lewis Wells Broadwell who worked as sales agent for the
Gatling Gun The Gatling gun is a rapid-firing multiple-barrel firearm invented in 1861 by Richard Jordan Gatling of North Carolina. It is an early machine gun and a forerunner of the modern electric motor-driven rotary cannon. The Gatling gun's operatio ...
Company in Europe replaced a papier-mache obturating cup in bag-loaded RBLs with a metallic gas ring and patented his invention in 1861, later perfecting it in 1864 and 1866; most countries paid royalties to Broadwell for the design, but in Germany the Krupp company stole it and used it for free.


French efforts

In the meantime the French persevered with trying to develop breechloaders which combined faster loading than muzzle-loaders, high power, safety and solved the problem of obturation. The Lahitolle 95 mm cannon of 1875 with an
interrupted screw file:Breech 122m10 hameenlinna 2.jpg, 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-loadi ...
breech met the first three requirements to a great extent and partially solved the obturation problem. Finally the de Bange system introduced in 1877 solved the obturation problem with an asbestos pad impregnated with grease which expanded and sealed the breech on firing. The de Bange system formed the obturation system for all subsequent screw breeches to the present day. Britain adopted the de Bange breech when it returned to breechloaders in the early 1880s after some initial experiments with the inferior "Armstrong cup" obturation system. Britain, France, and the United States preferred screw breeches for most calibres, but the major drawback of the de Bange interrupted screw as first implemented was that only half of the circumference of the breech block could be threaded, and hence it needed to be fairly long to achieve safe locking of the breech, which required three separate motions to open after firing; rotate to unscrew, retract the screw and swing to the side. Loading required the 3 operations in reverse. This was hence termed a "three motion block" and was slow to operate.


Welin breech block

While working as a weapons designer for Thorsten Nordenfelt in
London London is the Capital city, capital and List of urban areas in the United Kingdom, largest city of both England and the United Kingdom, with a population of in . London metropolitan area, Its wider metropolitan area is the largest in Wester ...
, Axel Welin solved this problem in 1889–1890 with his stepped
interrupted screw file:Breech 122m10 hameenlinna 2.jpg, 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-loadi ...
Welin breech block. This had threads in sets of steps of increasing diameter so that instead of only half of the screw being threaded, the fraction threaded was number of steps / (1 + number of steps): i.e. if the block of a large gun had four steps of threads, 80% of the screw was threaded, allowing a much shorter screw and hence breech block. This allowed the block to be unscrewed and swung out in two motions – the "two motion interrupted screw" breech.


Bofors ogival screw

Also in the early 1890s, Arent Silfversparre of Bofors invented an ogival screw breech, similar to the Armstrong model in the way it eliminated the need to withdraw the screw before swinging it to the side. Bofors continued to use this in medium artillery into the 20th century. The Elswick conical screw breech is very similar in concept.


The sliding block

The German company
Krupp Friedrich Krupp AG Hoesch-Krupp (formerly Fried. Krupp AG and Friedrich Krupp GmbH), trade name, trading as Krupp, was the largest company in Europe at the beginning of the 20th century as well as Germany's premier weapons manufacturer dur ...
in contrast, adopted "Horizontal sliding block" breeches, rather than screw breeches, for all artillery calibres up to naval guns. This was similar in some ways to the original "Armstrong screw"; the shot and powder cartridge were inserted through the open rear end of the breech into the gun bore, and a steel block was slid home into a horizontal slot cut through the breech to close the rear end of the breech. However, unlike Armstrong, Krupp loaded the powder propellant in a metal cartridge case much like a large
rifle A rifle is a long gun, long-barreled firearm designed for accurate shooting and higher stopping power, with a gun barrel, barrel that has a helical or spiralling pattern of grooves (rifling) cut into the bore wall. In keeping with their focus o ...
cartridge, which expanded against the chamber wall on firing and effectively sealed the breech. The sliding block, in both horizontal and vertical forms, and metal cartridge case continued to be the preferred German breech system until after
World War II World War II or the Second World War (1 September 1939 – 2 September 1945) was a World war, global conflict between two coalitions: the Allies of World War II, Allies and the Axis powers. World War II by country, Nearly all of the wo ...
(e.g. 7.5 cm Pak 40), and is still used by some modern artillery.


Quickfiring guns

The first quick-firing light gun was the 1-inch Nordenfelt gun, built in Britain from 1880. The gun was expressly designed to defend larger warships against the new small fast-moving
torpedo boat A torpedo boat is a relatively small and fast naval ship designed to carry torpedoes into battle. The first designs were steam-powered craft dedicated to ramming enemy ships with explosive spar torpedoes. Later evolutions launched variants of ...
s in the late 1870s to the early 1880s and was an enlarged version of the successful rifle-calibre Nordenfelt hand-cranked "machine gun" designed by Helge Palmcrantz. The gun fired a solid steel bullet with hardened tip and brass jacket. It was superseded for anti-torpedo boat defence in the mid-1880s by the new generation of Hotchkiss and Nordenfelt " QF" guns of 47-mm and 57-mm calibre firing exploding " common pointed" shells weighing . The French firm Hotchkiss produced the QF 3 pounder as a light 47-mm naval gun from 1886. The gun was ideal for defending against small fast vessels such as torpedo boats and was immediately adopted by the RN as the "Ordnance QF 3 pounder Hotchkiss".British forces traditionally denoted smaller ordnance by the weight of its standard projectile, in this case approximately . It was built under licence by Elswick Ordnance Company. Both the Hotchkiss and Nordenfelt guns loaded ammunition as a single cartridge with projectile, cartridge case and primer in a single unit. The cartridge case sealed the breech on firing and a vertical sliding wedge (block) locked it in place. These new guns incorporated recoil control devices which facilitated consistency of aim, allowed single-motion loading and could be fired as soon as the cartridge was inserted, and then ejected it after firing, these properties denoting a "quick-firing" gun. This set a new standard for artillery, and made firing cycles measured in seconds rather than minutes possible. Britain used brass cartridge cases for all calibres up to 6 inches in the late 1880s and early 1890s. However, British-designed quickfiring ("QF" in British terminology, which became synonymous with charges in metal cartridge cases) continued to use screw breech blocks, but with their function merely to lock the cartridge in place rather than provide obturation. The powerful backward force generated by 6-inch QF guns still required a strongly seated breech screw with as much thread as possible. However, a basic interrupted-thread screw sufficiently long enough to have enough thread to secure the cartridge on firing still required three separate motions to operate – rotate, withdraw, swing aside after firing, and repeated in reverse before firing. Elswick Ordnance Company (Armstrong's ordnance arm) developed a coned version of the interrupted-thread screw, with a decreasing rather than constant diameter towards the front. This eliminated the second "withdrawal" motion, with just two motions now necessary, rotate and swing aside. This proved short-lived, with Britain adopting charges in bags using the Welin stepped interrupted screw for all guns and up within several years of it becoming available.


See also

* Armstrong Gun * Anglo-German naval arms race


References

{{refs


External links


Royal New Zealand Artillery Association, Breech Mechanisms



Willian F Fullam & Thomas C Hart, USN, Text-Book of Ordnance and Gunnery. Chapter IV Breech Mechanisms
published by United States Naval Institute, Annapolis MD, 1905 Artillery by type