A smoothbore weapon is one that has a
barrel without
rifling. Smoothbores range from handheld
firearms to powerful
tank gun
A tank gun is the main armament of a tank. Modern tank guns are high-velocity, large-caliber artilleries capable of firing kinetic energy penetrators, high-explosive anti-tank, and cannon-launched guided projectiles. Anti-aircraft guns can a ...
s and large artillery
mortars.
History
![L16 smoothbore](https://upload.wikimedia.org/wikipedia/commons/9/98/L16_smoothbore.png)
Early firearms had smoothly bored barrels that fired
projectiles without significant spin.
To minimize inaccuracy-inducing tumbling during flight, their projectiles required an aerodynamically uniform shape, such as a
sphere
A sphere () is a geometrical object that is a three-dimensional analogue to a two-dimensional circle. A sphere is the set of points that are all at the same distance from a given point in three-dimensional space.. That given point is th ...
. 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 an observable phenomenon commonly associated with a spinning object moving through a fluid. The path of the spinning object is deflected in a manner not present when the object is not spinning. The deflection can be expl ...
will curve it off the intended trajectory when spinning on any axis not parallel to the direction of travel.
Rifling 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
Sectional density (often abbreviated SD) is the ratio of an object's mass to its cross sectional area with respect to a given axis. It conveys how well an object's mass is distributed (by its shape) to overcome resistance along that axis.
Secti ...
to be fired from the same
caliber 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'', while ''precision'' is how close the measurements are to each oth ...
,
effective range and
hitting power.
In the eighteenth century, the standard infantry arm was the smoothbore
musket; 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, inventor of the French Minié rifle, for muzzle-loading rifled muskets. It was invented in 1847 and came to prominence in the Crimean War and ...
increased their rate of fire to match that of smoothbores.
Artillery
Artillery is a class of heavy military ranged weapons that launch munitions far beyond the range and power of infantry firearms. Early artillery development focused on the ability to breach defensive walls and fortifications during siege ...
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 scre ...
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, 1861 – May 26, 1865; also known by other names) was a civil war in the United States. It was fought between the Union ("the North") and the Confederacy ("the South"), the latter formed by states ...
. However, heavy coast defense
Rodman smoothbores persisted in the US until 1900 due to the tendency of the Civil War's heavy
Parrott rifle
The Parrott rifle was a type of muzzle-loading rifled artillery weapon used extensively in the American Civil War.
Parrott rifle
The gun was invented by Captain Robert Parker Parrott, a West Point graduate. He was an American soldier and inven ...
s to burst and lack of funding for replacement weapons.
Current use
![Twin Sisters, San Jacinto](https://upload.wikimedia.org/wikipedia/commons/1/13/Twin_Sisters%2C_San_Jacinto.jpg)
Some smoothbore firearms are still used.
Small arms
![Grand Turk(28)](https://upload.wikimedia.org/wikipedia/commons/0/05/Grand_Turk%2828%29.jpg)
A
shotgun fires multiple, round
shot
Shot may refer to:
Arts, entertainment, and media
* ''Shot'' (album), by The Jesus Lizard
*''Shot, Illusion, New God'', an EP by Gruntruck
*'' Shot Rev 2.0'', a video album by The Sisters of Mercy
* "Shot" (song), by The Rasmus
* ''Shot'' (2017 f ...
; firing out of a rifled barrel would impart
centrifugal force
In Newtonian mechanics, the centrifugal force is an inertial force (also called a "fictitious" or "pseudo" force) that appears to act on all objects when viewed in a rotating frame of reference. It is directed away from an axis which is parall ...
s that result a doughnut-shaped pattern of shot (with a high projectile
density
Density (volumetric mass density or specific mass) is the substance's mass per unit of volume. The symbol most often used for density is ''ρ'' (the lower case Greek letter rho), although the Latin letter ''D'' can also be used. Mathematical ...
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" or "less-lethal" ammunition for the purpose of suppressing riots or apprehending suspects with minimal harm or risk. Less-lethal launchers may ...
, which fires
less-lethal
Non-lethal weapons, also called nonlethal weapons, less-lethal weapons, less-than-lethal weapons, non-deadly weapons, compliance weapons, or pain-inducing weapons are weapons intended to be less likely to kill a living target than conventional ...
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. Alth ...
s and
teargas
Tear gas, also known as a lachrymator agent or lachrymator (), sometimes colloquially known as "mace" after the early commercial aerosol, is a chemical weapon that stimulates the nerves of the lacrimal gland in the eye to produce tears. In ad ...
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: WC) is a chemical compound (specifically, 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 ...
or
depleted uranium, capable of piercing 40 mm of rolled homogeneous armor at a range of 1,000 m, and causing secondary fragmentation.
Artillery
![USSMonitor1862](https://upload.wikimedia.org/wikipedia/commons/f/fe/USSMonitor1862.3.ws.jpg)
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 gun
A tank gun is the main armament of a tank. Modern tank guns are high-velocity, large-caliber artilleries capable of firing kinetic energy penetrators, high-explosive anti-tank, and cannon-launched guided projectiles. Anti-aircraft guns can a ...
s 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 first tank with a smoothbore gun was the Soviet
T-62
The T-62 is a Soviet main battle tank that was first introduced in 1961. As a further development of the T-55 series, the T-62 retained many similar design elements of its predecessor including low profile and thick turret armour. In contras ...
, introduced into service in 1961. Today all main battle tanks field them except the British
Challenger 2
The FV4034 Challenger 2 (MOD designation "CR2") is a third generation British main battle tank (MBT) in service with the armies of the United Kingdom and Oman. It was designed and built by the British company Vickers Defence Systems (now known ...
and Indian
Arjun MBT
Arjun or Arjuna may refer to
People
* Arjun (name), a male given name (including a list of persons with the name)
* Arjuna, a character of the Hindu epic '' Mahabharata''
* Kartavirya Arjuna, a character in Hindu mythology
* Arjun (Firoz Khan) ...
, and prototype of the forthcoming British Challenger 3 has a smoothbore gun. While the 73 mm gun of the early Soviet
infantry fighting vehicles
An infantry fighting vehicle (IFV), also known as a mechanized infantry combat vehicle (MICV), is a type of armoured fighting vehicle used to carry infantry into battle and provide direct-fire support. The 1990 Treaty on Conventional Armed Forc ...
BMP-1
The BMP-1 is a Soviet amphibious tracked infantry fighting vehicle, in service 1966–present. BMP stands for ''Boyevaya Mashina Pyekhoty 1'' (russian: link=no, Боевая Машина Пехоты 1; БМП-1), meaning "infantry fighting ve ...
and
BMD-1
The BMD-1 is a Soviet airborne amphibious tracked infantry fighting vehicle, which was introduced in 1969 and first seen by the West in 1970. BMD stands for ''Boyevaya Mashina Desanta'' (Боевая Машина Десанта, which literally ...
was a smoothbore, their more recent successors
BMP-3 and
BMD-4 use a rifled 100 mm gun. The Russian navy conducted experiments with large-caliber smoothbore
naval artillery
Naval artillery is artillery mounted on a warship, originally used only for naval warfare and then subsequently used for shore bombardment and anti-aircraft roles. The term generally refers to tube-launched projectile-firing weapons and exclude ...
, which were halted by budget cuts.
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 is ...
(ACR) program. The ACR "rifles" used smoothbore barrels to fire single or multiple
flechettes (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 (also known as wound 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.
Bullet design (as well as the velocity of impact) larg ...
.
Mortar barrels are typically
muzzle-loading
A muzzleloader is any firearm into which the projectile and the propellant charge is loaded from the muzzle of the gun (i.e., from the forward, open end of the gun's barrel). This is distinct from the modern (higher tech and harder to make) desig ...
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.
See also
*
Rifling
*
Buck and ball
Buck and ball was a common load for muzzle-loading muskets, and was frequently used in the American Revolutionary War and into the early days of the American Civil War. The load usually consisted of a .50 to .75 caliber round lead musket ball t ...
*
Cap gun
A cap gun, cap pistol, or cap rifle is a toy gun that creates a loud sound simulating a gunshot and smoke when a small percussion cap is ignited. Cap guns were originally made of cast iron, but after World War II were made of zinc alloy, and mo ...
*
Caplock mechanism
The percussion cap or percussion primer, 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. This crucial invention gave rise ...
*
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
Tubes and primers are used to ignite the propellant in projectile weapons.
In ancient times various devices were adopted to ignition system, ignite the Explosive material, charge. Small guns were fired by priming powder poured down the touch hole ...
*
Minié ball
The Minié ball or Minie ball, is a type of hollow-based bullet designed by Claude-Étienne Minié, inventor of the French Minié rifle, for muzzle-loading rifled muskets. It was invented in 1847 and came to prominence in the Crimean War and ...
*
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, carbon (in the form of charcoal) and potassium nitrate (saltpeter). Th ...
*
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 ...
*
Muzzleloader
*
Muzzle (firearms)
*
Gun barrel
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-pressu ...
*
Projectile
References
{{reflist
Artillery by type
Firearm terminology
Artillery components