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{{More footnotes|date=February 2021}}
{{Cannon}}
A '''rifled breech loader''' (RBL) is an [[artillery]] piece which, unlike the [[smoothbore]] [[cannon]] and [[rifled muzzle loader]]
The spin imparted by the gun's [[rifling]] 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]] in [[fortification]] and [[ironclad]] warship design that
==Overview==
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The very first [[cannon]]s of the [[Middle Ages]] were breech loaded, with [[gunpowder]] 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, only [[Muzzle-loading|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===
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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]]. After the British artillery was shown up in the [[Crimean War]] as having barely changed since the [[Napoleonic Wars]] the industrialist [[William Armstrong, 1st Baron Armstrong|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]] at [[Woolwich]].<ref>{{cite journal|author=Marshall J. Bastable|title=From Breechloaders to Monster Guns: Sir William Armstrong and the Invention of Modern Artillery, 1854–1880|journal=Technology and Culture|year=1992|doi=10.2307/3105857|volume=33|issue=2|pages=213–247|jstor=3105857}}</ref><ref>{{cite web|url=http://www.gracesguide.co.uk/William_Armstrong|title=William Armstrong}}</ref>
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]] 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]] 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.{{citation-needed|reason=As of 2023, some British guns still use bagged charges, e.g., Royal Ordnance L30|date=April 2023}}
[[File:Sagahan Armstrong gun used at the Battle of Ueno against the Shogitai 1868.jpg|thumb|left|The [[Armstrong gun]] was a pivotal development for modern artillery as the first practical rifled breech loader. Pictured, deployed by [[Japan]] during the [[Boshin War]] (1868–69).]]
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===Broadwell ring===
{{main|Broadwell ring}}
American engineer [[Lewis Wells Broadwell]] who worked as sales agent for the [[Gatling Gun]] 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
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Finally the [[Charles Ragon de Bange|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===
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While working as a weapons designer for [[Thorsten Nordenfelt]] in [[London]], [[Axel Welin]] solved this problem in 1889–1890 with his stepped [[interrupted screw]] [[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.
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===Bofors ogival screw===
[[File:
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.
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===The sliding block===
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[[File:Figure423a Horizontal sliding-wedge breech operating mechanism.png|thumb|Diagram of the horizontal sliding wedge.]]
The German company [[Krupp]] in contrast, adopted "Horizontal sliding block" breeches, rather than screw breeches, for all artillery calibres up to {{convert|16
However, unlike Armstrong, Krupp loaded the powder propellant in a metal [[cartridge (firearms)|cartridge]] case much like a large [[rifle]] 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]] (e.g. [[7.5 cm Pak 40]]), and is still used by some modern artillery.
===Quickfiring guns===
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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]]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 et Cie|Hotchkiss]] and Nordenfelt "[[British ordnance terms#Fixed QF|QF]]" guns of 47-mm and 57-mm calibre firing exploding "[[British ordnance terms#Common pointed|common pointed]]" shells weighing {{convert|3–6
The French firm Hotchkiss produced the [[QF 3 pounder Hotchkiss|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".<ref>British forces traditionally denoted smaller ordnance by the weight of its standard projectile, in this case approximately {{convert|3|lb|kg}}.</ref> It was built under licence by [[Armstrong Whitworth#Elswick Ordnance Company|Elswick Ordnance Company]].
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[[File:QF 6 inch gun coned breech screw.jpg|thumb|left|[[Elswick Ordnance Company|Elswick]] coned interrupted screw breech of [[QF 6 inch /40 naval gun|QF 6-inch naval gun]].]]
[[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 {{convert|5
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▲These rapidly improving breech systems and the powerful new guns they facilitated led to an [[arms race]] in [[fortification]] and [[ironclad]] warship design that lead to the [[battleship]] class of [[HMS Dreadnought (1906)|HMS ''Dreadnought'']] and continued until the start of [[World War I]].
==See also==
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