Rifling of a Canon de 75 modèle 1897

A 35 caliber Remington, with a microgroove rifled barrel with a right hand twist. The French 75mm field gun was a quick-firing field Artillery piece developed in 1894 and which saw widespread service in World War I and served into The term caliber or calibre designates the interior Diameter of a tube or the exterior diameter of a wire or rod Remington Arms is a major American manufacturer of Rifles Shotguns other Firearms, Revolvers and Ammunition.

Rifling refers to helix-shaped pattern of grooves and lands that have been formed into the barrel of a firearm. A helix (pl helixes or helices) from the Greek word έλιξ, is a special kind of Space curve, i For the fictional characters see Gunbarrel (Transformers. A gun barrel is the tube usually Metal, through which a controlled Explosion A firearm is a Tool that projects either single or multiple Projectiles at high velocity through a controlled explosion It is the means by which a firearm imparts a spin to a projectile around its long axis, to gyroscopically stabilize it to improve accuracy and stability. A gyroscope is a device for measuring or maintaining orientation, based on the principles of Angular momentum.

Twist rate

For best performance, the barrel should have a twist rate sufficient to stabilize any bullet that it would reasonably be expected to fire, but not significantly more. A bullet is a solid Projectile propelled by a Firearm or Air gun and is normally made from metal (usually Lead) Large diameter bullets provide more stability, as the larger radius provides more gyroscopic inertia, while long bullets are harder to stabilize, as they tend to be very backheavy and the aerodynamic pressures have a longer "lever" to act on. In Physics, the angular momentum of a particle about an origin is a vector quantity equal to the mass of the particle multiplied by the Cross product of the position The slowest twist rates are found in muzzleloading firearms meant to fire a round ball; these will have twist rates as low as 1 in 60 inches (1,500 mm), or slightly longer, although for a typical multi-purpose muzzleloader rifle, a twist rate of 1 in 48 inches (1,200 mm) is very common. A muzzleloader is any Firearm into which the projectile and usually the Propellant charge is loaded from the muzzle of the Gun (i The M16A2 rifle, which is designed to fire the SS109 bullet, has a 1 in 7-inch (180 mm) twist. M16 (more formally United States Rifle II Caliber 556 mm M16) is the U 556x45mm NATO, standardized under STANAG 4172 is a Rifle cartridge. Civilian AR-15 rifles are commonly found with 1 in 12 inches (300 mm) for older rifles and 1 in 9 inches (230 mm) for most newer rifles, although some are made with 1 in 7 inches (180 mm) twist rates, the same as used for the M16. AR-15 (for Ar malite model 15, often mistaken for A utomatic R ifle is the common name for the widely-owned semi-automatic Rifles, which generally fire longer, smaller diameter bullets, will in general have higher twist rates than handguns, which fire shorter, larger diameter bullets.

George Greenhill, a mathematician at Emmanuel College, Cambridge, UK, developed a rule of thumb for use in calculating twist rates for a given lead-core bullet. Emmanuel College is a constituent college of the University of Cambridge, founded in 1584 by Sir Walter Mildmay on the site of a Dominican friary A rule of thumb is a principle with broad application that is not intended to be strictly accurate or reliable for every situation The formula, named the Greenhill Formula in his honour, is:

where:

• C = 150 (use 180 for muzzle velocities higher than 2,800 f/s)
• D = bullet's diameter in inches
• L = bullet's length in inches
• SG = bullet's specific gravity (10. Specific gravity is defined as the ratio of the Density of a given solid or liquid substance to the density of water at a specific temperature and pressure typically 9 for lead-core bullets, which cancels out the second half of the equation)

The original value of C was 150, which yields a twist rate in inches per turn, when given the diameter D and the length L of the bullet in inches. This works to velocities of about 2800 ft/s; above those velocities, a C of 180 should be used. For instance, with a velocity of 2000 ft/s, a diameter of 0. 5 inches (13 mm) and a length of 1. 5 inches (38 mm), the Greenhill formula would give a value of 30, which means 1 turn in 30 inches (760 mm).

A Parrot Rifled Cannon. These were often used by both the Confederate and Union forces in the American Civil War. The War Department was established by the Confederate Congress in an act on February 21, 1861. The Union Army was the army that fought for the Union during the American Civil War. Causes of the war See also Origins of the American Civil War, Timeline of events leading to the American Civil War The coexistence of a slave-owning South

If an insufficient twist rate is used, the bullet will begin to yaw and then tumble; this is usually seen as "keyholing", where bullets leave elongated holes in the target as they strike at an angle. Once the bullet starts to yaw, any hope of accuracy is lost, as the bullet will begin to veer off in random directions as it precesses. Precession refers to a change in the direction of the axis of a rotating object

Conversely, too-high a rate of twist can also cause problems. The excessive twist can cause accelerated barrel wear, and in high velocity bullets, an excessive twist can cause a very high spin rate in excess of the bullet's burst speed (see centripetal force). The centripetal force is the external force required to make a body follow a curved path A higher twist than needed can also cause more subtle problems with accuracy: Any inconsistency in the bullet, such as a void that causes an unequal distribution of mass, may be magnified by the spin. Undersized bullets also have problems, as they may not enter the rifling exactly concentric and coaxial to the bore, and excess twist will exacerbate the accuracy problems this causes. Concentric objects share the same center, axis or origin with one inside the other In Geometry, coaxial means that two or more forms share a common axis; it is the three- Dimensional linear analog of " Concentric " Lastly, excessive spinning causes a reduction in the lateral kinetic energy of a projectile, thereby reducing its destructive power (the energy instead becomes rotational kinetic energy). The kinetic energy of an object is the extra Energy which it possesses due to its motion

Manufacture

A tank's main gun is often rifled.

Most rifling is created by either:

• cutting one groove at a time with a machine tool, called cut rifling or single point cut rifling
• cutting all grooves in one pass with a special progressive broaching bit, called broached rifling
• pressing all grooves at once with a tool called a "button" that is pushed or pulled down the barrel, called button rifling
• forging the barrel over a mandrel containing a reverse image of the rifling (and often the chamber as well), called hammer forged
• flow forming the barrel preform over a mandrel containing a reverse image of the rifling, called rifling by flow forming. A machine tool is a powered mechanical device typically used to fabricate metal components of machines by Machining, which is the selective removal of metal Introduction A press, or a machine press is a Tool used to work Metal (typically Steel) by changing its shape and internal structure A forge is the workplace of a smith or a Blacksmith. A forge is sometimes referred to as a smithy. For the fictional characters see Gunbarrel (Transformers. A gun barrel is the tube usually Metal, through which a controlled Explosion A mandrel (ˈmændrɨl and also spelled mandril; in American English also called an arbor) is either an object used to shape machined work a Tool Flow Forming is a Metal forming technique in which a disk or tube of metal is formed over a mandrel by a roller using tremendous pressure A barrel or cask is a hollow cylindrical container traditionally made of Wood Staves and bound with Iron Hoops The A mandrel (ˈmændrɨl and also spelled mandril; in American English also called an arbor) is either an object used to shape machined work a Tool A new developed method by MACDOR company Turkey. Turkey (Türkiye known officially as the Republic of Turkey ( is a Eurasian Country that stretches

The grooves are the spaces that are cut out, and the resulting ridges are called 'lands'. A LAND attack is a DoS (Denial of Service attack that consists of sending a special poison spoofed packet to a computer causing it to lock up These lands and grooves can vary in number, depth, shape, direction of twist ('right' or 'left'), and 'twist rate' (turns per unit of barrel length). Twist rate is a Gun term that refers to the rate of twist of a Gun barrel 's Rifling grooves The spin imparted by rifling significantly improves the stability of the projectile, improving both range and accuracy. Typically rifling is a constant rate down the barrel, usually measured by the length of travel required to produce a single turn. Occasionally firearms are encountered with a gain twist, where the rate of spin increases from chamber to muzzle. While intentional gain twists are rare, due to manufacturing variance, a slight gain twist is in fact fairly common. Since a reduction in twist rate is very detrimental to accuracy, gunsmiths who are machining a new barrel from a rifled blank will often measure the twist carefully so they may put the faster rate, no matter how minute the difference is, at the muzzle end (see internal ballistics for more information on accuracy and bore characteristics). A gunsmith is a person who repairs modifies designs or builds Firearms to factory or customer specifications using Hand tools and Machine shop tools (such Conventional Machining, one of the most important material removal methods is a collection of material-working processes in which power-driven Machine tools, such as lathes Internal ballistics, a subfield of Ballistics, is the study of a Projectile 's behavior from the time its Propellant 's igniter is initiated until it exits

Typically in modern, smokeless powder, small firearms, the diameter of the bullet matches the diameter of the circle that encompasses the bottoms of the rifled grooves, the groove diameter. The bore diameter is smaller, being measured across the tops of the lands. A LAND attack is a DoS (Denial of Service attack that consists of sending a special poison spoofed packet to a computer causing it to lock up When the cartridge is fired, the bullet is forced into the barrel and the rifling engages the bullet, engraving it with an impression of the rifling. A cartridge (also known as a "round" packages the Bullet, Gunpowder and primer into a single metallic case precisely made to fit the As the bullet is propelled down the barrel, it begins to spin. This rate of spin is dictated by a bullet's muzzle velocity and the twist rate of the rifling. Twist rate is a Gun term that refers to the rate of twist of a Gun barrel 's Rifling grooves As mentioned earlier, for a given caliber, faster rates of twist are needed to stabilize longer bullets.

In contrast, in modern, black powder, small firearms that utilize patched bullets, the diameter of the bullet is usually chosen to be slightly smaller than this, being typically 0. 015 inches in diameter less than the diameter of the circle that encompasses the bottoms of the rifled grooves. This is done to permit using a patch that may be, say, 0. 010 inches thick, nominal, uncompressed. Folded over the bullet, the nominally 0. 010 inch thick patch will then compress from 0. 020 inches (accounting for the two thicknesses of the patch) down to 0. 015 inches, thereby forming a tight fit of the bullet with the rifling.

The diameters of bullets fired from a rifled barrel should ideally be at or slightly under the groove diameter, for the reasons as previously discussed, but should definitely be larger than the bore diameter. A bullet that is too large will have to swage down to fit in the bore, which can cause excessive and potentially unsafe pressures, as well as causing bullet irregularities to form that may affect accuracy, while a bullet that is too small will lose velocity and either leak gas or obturate at an angle, likewise providing poor accuracy. Swaging ( pronunciation note below) is a Metal -forming technique in which the dimensions of an item are altered using a die or dies into which the item Obturate means to block or obstruct In conventional English usage obturation refers specifically to the condition of being obstructed or occluded or the action of blocking stopping

History

The history of rifling a barrel is covered in depth in the article Rifle. A rifle is a Firearm designed to be fired from the shoulder with a barrel that has a helical groove or pattern of grooves ("rifling" cut into the barrel walls

Recent developments

The grooves most commonly used in modern rifling have fairly sharp edges. More recently, polygonal rifling, a throwback to the earliest types of rifling, has become popular, especially in handguns. Polygonal rifling is a type of Rifling wherein the traditional lands and grooves are replaced by "hills and valleys" in a rounded Polygonal pattern usually Polygonal barrels tend to have longer service lives because the reduction of the sharp edges of the land reduces erosion of the barrel. Supporters of polygonal rifling also claim higher velocities and greater accuracy. Polygonal rifling is currently seen on pistols from Heckler & Koch, Glock and Kahr Arms, as well as the Desert Eagle. Heckler & Koch GmbH ( H&K) (pronounced ˈhɛklɐʔʊntˈkɔx is a German defense manufacturing company that produces various Glock GmbH (trademarked as GLOCK) is a weapons manufacturer of handguns that are trade marked as "Safe Action Pistols Kahr Arms is an American Small arms manufacturer founded by Kook Jin "Justin" Moon (son of Unification Church founder Sun Myung The Desert Eagle is a large caliber gas-operated Semi-automatic pistol manufactured primarily in Israel by IMI ( Israel Military Industries,

For tanks and artillery pieces, the extended range, full bore concept developed by Gerald Bull for the GC-45 howitzer reverses the normal rifling idea by using a shell with small fins that ride in the grooves, as opposed to using a slightly oversized projectile which is forced into the grooves. Gerald Vincent Bull ( March 9, 1928 - March 22, 1990) was a Canadian engineer who developed long range Artillery. The GC-45 ( Gun Canada 45- Calibre) is a 155 mm Howitzer designed by Gerald Bull 's Space Research Corporation (SRC in the 1970s Such guns have achieved significant increases in muzzle velocity and range. Examples include the South African G5 and the German PzH 2000. The Republic of South Africa (also known by other official names) is a country located at the southern tip of the continent of Africa The G5 is a South African towed Howitzer of 155 mm calibre manufactured by Denel. Germany, officially the Federal Republic of Germany ( ˈbʊndəsʁepuˌbliːk ˈdɔʏtʃlant is a Country in Central Europe. The Panzerhaubitze 2000 ("Armoured howitzer 2000" abbreviated PzH 2000, is a German 155mm self-propelled howitzer developed by Krauss-Maffei

See also

• Comparison Microscope
• Gun barrel
• Smoothbore
• Polygonal rifling

References

External links

• Article on barrel making from an IHMSA shooter
• Rifling By Flow Forming A new developed method for rifling. A comparison microscope, sometimes known also as Stereomicroscope or dissecting microscope is a device used to analyze side-by-side specimens For the fictional characters see Gunbarrel (Transformers. A gun barrel is the tube usually Metal, through which a controlled Explosion Smoothbore refers to a Firearm or Cannon which does not have a rifled barrel. Polygonal rifling is a type of Rifling wherein the traditional lands and grooves are replaced by "hills and valleys" in a rounded Polygonal pattern usually Metallic silhouette shooting is a group of Target shooting disciplines that involves shooting at Metal cutouts representing Game animals at varying distances
• Article on barrel making from Lilja, a maker of world class competition barrels
• Article on making and measuring rifling by Lilja; includes pictures of button rifling machine
• 6mmBR article on barrels
• Bore slugging tutorial, explaining now to determine the true bore and groove size and choose appropriate bullet diameters