In firearm

Firearm

A firearm is a weapon that launches one, or many, projectile at high velocity through confined burning of a propellant. This subsonic burning process is technically known as deflagration, as opposed to supersonic combustion known as a detonation. In older firearms, the propellant was typically...

s terminology, fluting refers to the removal of material from a cylindrical

Cylinder (geometry)

A cylinder is one of the most basic curvilinear geometric shapes, the surface formed by the points at a fixed distance from a given line segment, the axis of the cylinder. The solid enclosed by this surface and by two planes perpendicular to the axis is also called a cylinder...

 surface, usually creating grooves. This is most often the barrel

Gun barrel

A gun barrel is the tube, usually metal, through which a controlled explosion or rapid expansion of gases are released in order to propel a projectile out of the end at a high velocity....

 of a rifle

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 cut into the barrel walls. The raised areas of the rifling are called "lands," which make contact with the projectile , imparting spin around an axis corresponding to the...

, though it may also refer to the cylinder

Cylinder (firearms)

In firearms terminology, the Cylinder refers to the cylindrical, rotating part of a revolver containing multiple cartridge chambers. The cylinder revolves around a central axis in the revolver to bring each individual chamber into alignment with the barrel for firing...

 of a revolver

Revolver

A revolver is a repeating firearm that has a cylinder containing multiple chambers and at least one barrel for firing. The first revolver ever made was built by Elisha Collier in 1818. The percussion cap revolver was invented by Samuel Colt in 1836. This weapon became known as the Colt Paterson...

 or the bolt

Bolt (firearm)

A bolt is a mechanical part of a firearm that blocks the rear of the chamber while the propellant burns.In manually-operated firearms, such as bolt-action, lever-action, and pump-action rifles and shotguns, the bolt is held fixed by its locking lugs during firing, forcing all the expanding gas...

 of a bolt action rifle.
In contrast to rifle barrels and revolver cylinders rifle bolts are normally helically

Helix

A helix is a type of smooth space curve, i.e. a curve in three-dimensional space. It has the property that the tangent line at any point makes a constant angle with a fixed line called the axis. Examples of helixes are coil springs and the handrails of spiral staircases. A "filled-in" helix – for...

 fluted, though helical fluting is sometimes also applied to rifle barrels.

The main purpose of fluting is to reduce weight, and to a lesser extent increase rigidity

Stiffness

Stiffness is the resistance of an elastic body to deformation by an applied force along a given degree of freedom when a set of loading points and boundary conditions are prescribed on the elastic body.-Calculations:...

 for a given total weight or increase surface area

Surface area

Surface area is the measure of how much exposed area a solid object has, expressed in square units. Mathematical description of the surface area is considerably more involved than the definition of arc length of a curve. For polyhedra the surface area is the sum of the areas of its faces...

 to make the barrels less susceptible for overheating

Thermal shock

Thermal shock is the name given to cracking as a result of rapid temperature change. Glass and ceramic objects are particularly vulnerable to this form of failure, due to their low toughness, low thermal conductivity, and high thermal expansion coefficients...

 for a given total weight. However, for a given diameter

Diameter

In geometry, a diameter of a circle is any straight line segment that passes through the center of the circle and whose endpoints are on the circle. The diameters are the longest chords of the circle...

, a non-fluted barrel will be stiffer and be able to absorb a larger amount of heat at the price of additional total weight.
The PGM Ultima Ratio

PGM Ultima Ratio

The PGM Ultima Ratio is a French-designed and manufactured sniper rifle. It uses the 7.62x51 mm NATO cartridge and can, depending on the variant, be chambered for several other cartridges. The PGM Ultima Ratio is intended to fulfill an anti-personnel role and is produced by PGM Précision of France...

sniper rifle along its Intervention barrel configuration features a series of heat dispersion ribs perpendicular to the bore axis. Several other Ultima Ratio barrel configurations feature more traditional fluting grooves running parallel to the bore axis.