Smoothbore
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A smoothbore weapon is one that has a
barrel A barrel or cask is a hollow cylindrical container with a bulging center, longer than it is wide. They are traditionally made of wooden stave (wood), staves and bound by wooden or metal hoops. The word vat is often used for large containers ...
without
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 ...
. Smoothbores range from handheld
firearms A firearm is any type of gun that uses an explosive charge and is designed to be readily carried and operated by an individual. The term is legally defined further in different countries (see legal definitions). The first firearms originated ...
to powerful tank guns and large artillery mortars. Some examples of smoothbore weapons are muskets, blunderbusses, and flintlock pistols. The opposite of smoothbore is
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 ...
.


History

Early firearms had smoothly bored barrels that fired
projectile A projectile is an object that is propelled by the application of an external force and then moves freely under the influence of gravity and air resistance. Although any objects in motion through space are projectiles, they are commonly found ...
s without significant spin. To minimize inaccuracy-inducing tumbling during flight, their projectiles required an aerodynamically uniform shape, such as a
sphere A sphere (from Ancient Greek, Greek , ) is a surface (mathematics), surface analogous to the circle, a curve. In solid geometry, a sphere is the Locus (mathematics), set of points that are all at the same distance from a given point in three ...
. However, surface imperfections on the projectile and/or the barrel will cause even a sphere to rotate randomly during flight, and the
Magnus effect The Magnus effect is a phenomenon that occurs when a spin (geometry), spinning Object (physics), object is moving through a fluid. A lift (force), lift force acts on the spinning object and its path may be deflected in a manner not present when ...
will curve it off the intended trajectory when spinning on any axis not parallel to the direction of travel.
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 ...
the bore surface with spiral grooves or polygonal valleys imparts a stabilizing
gyroscopic A gyroscope (from Ancient Greek γῦρος ''gŷros'', "round" and σκοπέω ''skopéō'', "to look") is a device used for measuring or maintaining orientation and angular velocity. It is a spinning wheel or disc in which the axis of rot ...
spin to a projectile that prevents tumbling in flight. Not only does this more than counter Magnus-induced drift, but it allows a longer, more streamlined round with greater sectional density to be fired from the same
caliber In guns, particularly firearms, but not #As a measurement of length, artillery, where a different definition may apply, caliber (or calibre; sometimes abbreviated as "cal") is the specified nominal internal diameter of the gun barrel Gauge ( ...
barrel, improving the
accuracy Accuracy and precision are two measures of ''observational error''. ''Accuracy'' is how close a given set of measurements (observations or readings) are to their ''true value''. ''Precision'' is how close the measurements are to each other. The ...
,
effective range Effective range is a term with several definitions depending upon context. Distance Effective range may describe a distance between two points where one point is subject to an energy release at the other point. The source, receiver, and conditio ...
and hitting power. In the eighteenth century, the standard infantry arm was the smoothbore
musket A musket is a muzzle-loaded long gun that appeared as a smoothbore weapon in the early 16th century, at first as a heavier variant of the arquebus, capable of penetrating plate armour. By the mid-16th century, this type of musket gradually dis ...
; although rifled muskets were introduced in the early 18th century and had more power and range, they did not become the norm until the middle of the 19th century, when the
Minié ball The Minié ball, or Minie ball, is a type of hollow-based bullet designed by Claude-Étienne Minié for muzzle-loaded, rifled muskets. Invented in 1846 shortly followed by the Minié rifle, the Minié ball came to prominence during the Crime ...
increased their rate of fire to match that of smoothbores.
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 ...
weapons were smoothbore until the mid-19th century, and smoothbores continued in limited use until the late 19th century. Early rifled artillery pieces were patented by
Joseph Whitworth Sir Joseph Whitworth, 1st Baronet (21 December 1803 – 22 January 1887) was an English engineer, entrepreneur, inventor and philanthropist. In 1841, he devised the British Standard Whitworth system, which created an accepted standard for screw ...
and William Armstrong in the United Kingdom in 1855. In the United States, rifled small arms and artillery were gradually adopted during the
American Civil War The American Civil War (April 12, 1861May 26, 1865; also known by Names of the American Civil War, other names) was a civil war in the United States between the Union (American Civil War), Union ("the North") and the Confederate States of A ...
. However, heavy coast defense Rodman smoothbores persisted in the US until 1900 due to the tendency of the Civil War's heavy Parrott rifles to burst and lack of funding for replacement weapons.


Current use

Some smoothbore firearms are still used.


Small arms

A
shotgun A shotgun (also known as a scattergun, peppergun, or historically as a fowling piece) is a long gun, long-barreled firearm designed to shoot a straight-walled cartridge (firearms), cartridge known as a shotshell, which discharges numerous small ...
fires multiple, round shot; firing out of a rifled barrel would impart
centrifugal force Centrifugal force is a fictitious force in Newtonian mechanics (also called an "inertial" or "pseudo" force) that appears to act on all objects when viewed in a rotating frame of reference. It appears to be directed radially away from the axi ...
s that result a doughnut-shaped pattern of shot (with a high projectile
density Density (volumetric mass density or specific mass) is the ratio of a substance's mass to its volume. The symbol most often used for density is ''ρ'' (the lower case Greek letter rho), although the Latin letter ''D'' (or ''d'') can also be u ...
on the periphery, and a low projectile density in the interior). While this may be acceptable at close ranges (some spreader chokes are rifled to produce wide patterns at close range) this is not desirable at longer ranges, where a tight, consistent pattern is required to improve accuracy. Another smoothbore weapon in use today is the 37-mm
riot gun In current usage, a riot gun or less-lethal launcher is a type of firearm used to fire Non-lethal weapon, "non-lethal" or "less-lethal" ammunition for the purpose of suppressing riots or apprehending suspects with minimal harm or risk. Less-leth ...
, which fires less-lethal munitions like
rubber bullet Rubber bullets (also called rubber baton rounds) are a type of baton round. Despite the name, rubber bullets typically have either a metal core with a rubber coating, or are a homogeneous admixture with rubber being a minority component. Altho ...
s and teargas at short range at crowds, where a high degree of accuracy is not required. The Steyr IWS 2000 anti-tank rifle is smoothbore. This can help accelerate projectiles and increase ballistic effectiveness. The projectile is a 15.2 mm fin-stabilized discarding-sabot type with armor-piercing capability which the IWS 2000 was specifically designed to fire. It contains a dart-shaped penetrator of either
tungsten carbide Tungsten carbide (chemical formula: ) is a carbide containing equal parts of tungsten and carbon atoms. In its most basic form, tungsten carbide is a fine gray powder, but it can be pressed and formed into shapes through sintering for use in in ...
or
depleted uranium Depleted uranium (DU), also referred to in the past as Q-metal, depletalloy, or D-38, is uranium with a lower content of the fissile isotope Uranium-235, 235U than natural uranium. The less radioactive and non-fissile Uranium-238, 238U is the m ...
, capable of piercing 40 mm of rolled homogeneous armor at a range of 1,000 m, and causing secondary fragmentation.


Artillery and tanks

The cannon made the transition from smoothbore firing cannonballs to rifled firing shells in the mid-19th century. However, to reliably penetrate the thick armor of modern armored vehicles many modern tank guns have moved back to smoothbore. These fire a very long, thin kinetic-energy projectile, too long in relation to its diameter to develop the necessary spin rate through rifling. Instead, kinetic energy rounds are produced as fin-stabilized darts. Not only does this reduce the time and expense of producing rifled barrels, it also reduces the need for replacement due to barrel wear. The armour-piercing gun evolution has also shown up in small arms, particularly the now abandoned U.S.
Advanced Combat Rifle The Advanced Combat Rifle (ACR) was a United States Army program, started in 1986, to find a replacement for the M16 assault rifle. Under the stress of battle the average soldier with an M16 may shoot a target at 45 meters, but hit probability i ...
(ACR) program. The ACR "rifles" used smoothbore barrels to fire single or multiple
flechette A flechette or flèchette ( ) is a pointed, fin-stabilized steel projectile. The name comes from French (from \''wikt:flèche, flèche''), meaning "little arrow" or "Dart (missile), dart", and sometimes retains the grave accent in English: flè ...
s (tiny darts), rather than bullets, per pull of the trigger, to provide long range, flat trajectory, and armor-piercing abilities. Just like kinetic-energy tank rounds, flechettes are too long and thin to be stabilized by rifling and perform best from a smoothbore barrel. The ACR program was abandoned due to reliability problems and poor
terminal ballistics Terminal ballistics is a sub-field of ballistics concerned with the behavior and effects of a projectile when it hits and transfers its energy to a target. This field is usually cited in forensic ballistics. Bullet design (as well as the veloci ...
. Mortar barrels are typically
muzzle-loading A muzzleloader is any firearm in which the user loads the projectile and the propellant charge into the muzzle end of the gun (i.e., from the forward, open end of the gun's barrel). This is distinct from the modern designs of breech-loading fire ...
smoothbores. Since mortars fire bombs that are dropped down the barrel and must not be a tight fit, a smooth barrel is essential. The bombs are fin-stabilized.


Gallery


See also

*
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 ...
* Buck and ball * Cap gun *
Caplock mechanism The percussion cap, percussion primer, or caplock, introduced in the early 1820s, is a type of single-use percussion ignition device for muzzle loader firearm locks enabling them to fire reliably in any weather condition. Its invention gave ...
*
Internal ballistics Internal ballistics (also interior ballistics), a subfield of ballistics, is the study of the propulsion of a projectile. In guns, internal ballistics covers the time from the propellant's ignition until the projectile exits the gun barrel. The s ...
* Tubes and primers for ammunition *
Minié ball The Minié ball, or Minie ball, is a type of hollow-based bullet designed by Claude-Étienne Minié for muzzle-loaded, rifled muskets. Invented in 1846 shortly followed by the Minié rifle, the Minié ball came to prominence during the Crime ...
*
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 ...
*
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 ...
*
Muzzleloader A muzzleloader is any firearm in which the user loads the bullet, projectile and the propellant charge into the Muzzle (firearms), muzzle end of the gun (i.e., from the forward, open end of the gun's barrel). This is distinct from the modern desi ...
*
Muzzle (firearms) A gun barrel is a crucial part of gun-type weapons such as small firearms, artillery pieces, and air guns. It is the straight shooting tube, usually made of rigid high-strength metal, through which a contained rapid expansion of high-pressure ...
*
Gun barrel A gun barrel is a crucial part of gun-type weapons such as small arms, small firearms, artillery pieces, and air guns. It is the straight shooting tube, usually made of rigid high-strength metal, through which a contained rapid expansion of high ...
*
Projectile A projectile is an object that is propelled by the application of an external force and then moves freely under the influence of gravity and air resistance. Although any objects in motion through space are projectiles, they are commonly found ...


References

{{reflist Artillery by type Firearm terminology Artillery components