Rifled breech loader
Encyclopedia
A rifled breech loader is an artillery
piece which, unlike the smooth-bore 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.
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.
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.
The very first cannons 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. Muzzle-loaders were then used until the 19th century.
In 1837 Martin von Wahrendorff
patented a breech-loader with a cylindrical breech plug secured by a horizontal wedge; it was adopted by Sweden in 1854.
In 1861 Street & Hungerford Company produced Hughes cannon. It's a breech-loader with the breech of the cannon is uniquely like a bolt-action but has no firing pin in its bolt.
Armstrong introduced improved designs in the 1850s and 1860s ("Armstrong gun
s" with his "Armstrong screw" breech) which 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 : 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 and Royal Navy, 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
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
. 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.
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.
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.
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.
Further improvements such as that of Smith-Asbury in 1916 allowed the whole action of unscrewing and swinging aside of the breech screw to be accomplished in a single continuous motion, resulting in the "single-motion interrupted screw breech" still in use today.
in fortification
and ironclad warship design that lead to the battleship
class of HMS Dreadnought (1906)
and continued until the start of World War I
.
Artillery
Originally applied to any group of infantry primarily armed with projectile weapons, artillery has over time become limited in meaning to refer only to those engines of war that operate by projection of munitions far beyond the range of effect of personal weapons...
piece which, unlike the smooth-bore cannon
Cannon
A cannon is any piece of artillery that uses gunpowder or other usually explosive-based propellents to launch a projectile. Cannon vary in caliber, range, mobility, rate of fire, angle of fire, and firepower; different forms of cannon combine and balance these attributes in varying degrees,...
and rifled muzzle loader (RML) which preceded it, has rifling
Rifling
Rifling is the process of making helical grooves in the barrel of a gun or firearm, which imparts a spin to a projectile around its long axis...
in the barrel and is loaded from the breech
Breech-loading weapon
A breech-loading weapon is a firearm in which the cartridge or shell is inserted or loaded into a chamber integral to the rear portion of a barrel....
at the rear of the gun.
The spin imparted by the gun's rifling
Rifling
Rifling is the process of making helical grooves in the barrel of a gun or firearm, which imparts a spin to a projectile around its long axis...
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.
Overview
The major problem to be solved with breechloading artillery was obturation : the sealing of the breech after firing to ensure that none of the gases generated by the burning of the propellant (initially gunpowder) 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.
Early breechloaders
In 1837 Martin von Wahrendorff
Martin von Wahrendorff
Martin von Wahrendorff was a Swedish diplomat and inventor.His father Anders von Wahrendorff was the owner of the gun foundry at Åker. In 1837 Wahrendorff applied for patent on a new breech mechanism, later known as the Wahrendorff breech. The first breech loaded Wahrendorff gun was manufactured...
patented a breech-loader with a cylindrical breech plug secured by a horizontal wedge; it was adopted by Sweden in 1854.
In 1861 Street & Hungerford Company produced Hughes cannon. It's a breech-loader with the breech of the cannon is uniquely like a bolt-action but has no firing pin in its bolt.
Armstrong screw breech
Armstrong Gun
The term Armstrong Gun was primarily used to describe the unique design of the rifled breech-loading field and heavy guns designed by Sir William Armstrong and manufactured in England from 1855 by the Elswick Ordnance Company and the Royal Arsenal at Woolwich...
s" with his "Armstrong screw" breech) which 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 : 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 and Royal Navy, 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
Boshin War
The was a civil war in Japan, fought from 1868 to 1869 between forces of the ruling Tokugawa shogunate and those seeking to return political power to the imperial court....
to devastate the Aizu
Aizu
is an area comprising the westernmost third of Fukushima Prefecture in Japan. The principal city of the area is Aizuwakamatsu.During the Edo period, Aizu was a feudal domain known as and part of Mutsu Province.-History:...
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
Second Opium War
The Second Opium War, the Second Anglo-Chinese War, the Second China War, the Arrow War, or the Anglo-French expedition to China, was a war pitting the British Empire and the Second French Empire against the Qing Dynasty of China, lasting from 1856 to 1860...
. 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.
Interrupted screw breech
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 : i.e. how to prevent escape of some propellant gas through the breech to the rear. The Lahitolle 95 mm cannon of 1875 with an interrupted screwInterrupted screw
An interrupted screw or interrupted thread is a mechanical device typically used in the breech of artillery guns. It was invented circa 1845....
breech met the first three requirements to a great extent and partially solved the obturation problem.
de Bange system
Charles Ragon de Bange
Charles Ragon de Bange , often simply called de Bange, was a Polytechnician and a French artillery colonel of the 19th century. He invented the first effective obturator system for breech-loading artillery. Its basic principle of functioning is still widely in use to this day...
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.
Krupp sliding block
Krupp in Germany during this period (1864 - 1880s) in contrast adopted "Horizontal sliding block" breeches, rather than screw breeches, for all artillery calibres up to 16 inch naval guns. This was similar in some ways to the original "Armstrong screw" : the shell 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 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, and is still used by some modern artillery.Hotchkiss and Nordenfelt sliding-wedge quickfiring guns
From the mid-1880s Hotchkiss and Nordenfelt introduced 47-mm and 57-mm guns which loaded ammunition as a single cartridge with projectile, cartridge case and primer in a single unit as with modern rifle cartridges. 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 fired as soon as the cartridge was inserted and ejected it after firing : hence the name quick-firing. This set a new standard for artillery, and made firing cycles measured in seconds rather than minutes possible.Elswick coned interrupted screw
Britain enthusiastically adopted the new quickfiring technology, using brass cartridge cases for all calibres up to 6 inches in the late 1880s and early 1890s. However, unlike Krupp and Hotchkiss, 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 5 inches and up within several years of it becoming available.Bofors ogival screw
Also in the early 1890s, Arent Silfversparre of BoforsBofors
The name Bofors has been associated with the iron industry for more than 350 years.Located in Karlskoga, Sweden, the company originates from the hammer mill "Boofors" founded 1646. The modern corporate structure was created in 1873 with the foundation of Aktiebolaget Bofors-Gullspång...
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.
Welin stepped interrupted screw breech
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. Axel WelinAxel Welin
Axel Welin , was a Swedish inventor and industrialist.Ernst Axel Martin Welin studied at the Royal Institute of Technology in Stockholm from 1879 to 1884. Between 1886 and 1888, Welin worked as a weapons designer for Thorsten Nordenfelt in London. In 1889 he started his own engineering firm, the...
solved this problem in 1889-1890 with his stepped interrupted screw Welin breech block
Welin breech block
The Welin breech block was a revolutionary stepped, interrupted thread design for locking artillery breeches, invented by Axel Welin in 1889 or 1890...
. 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.
Further improvements such as that of Smith-Asbury in 1916 allowed the whole action of unscrewing and swinging aside of the breech screw to be accomplished in a single continuous motion, resulting in the "single-motion interrupted screw breech" still in use today.
Summary
These rapidly-improving breech systems and the powerful new guns they facilitated led to an arms raceArms race
The term arms race, in its original usage, describes a competition between two or more parties for the best armed forces. Each party competes to produce larger numbers of weapons, greater armies, or superior military technology in a technological escalation...
in fortification
Fortification
Fortifications are military constructions and buildings designed for defence in warfare and military bases. Humans have constructed defensive works for many thousands of years, in a variety of increasingly complex designs...
and ironclad warship design that lead to the battleship
Battleship
A battleship is a large armored warship with a main battery consisting of heavy caliber guns. Battleships were larger, better armed and armored than cruisers and destroyers. As the largest armed ships in a fleet, battleships were used to attain command of the sea and represented the apex of a...
class of HMS Dreadnought (1906)
HMS Dreadnought (1906)
HMS Dreadnought was a battleship of the British Royal Navy that revolutionised naval power. Her entry into service in 1906 represented such a marked advance in naval technology that her name came to be associated with an entire generation of battleships, the "dreadnoughts", as well as the class of...
and continued until the start of World War I
World War I
World War I , which was predominantly called the World War or the Great War from its occurrence until 1939, and the First World War or World War I thereafter, was a major war centred in Europe that began on 28 July 1914 and lasted until 11 November 1918...
.