Fluting is the removal of material from a

cylindrical A cylinder () has traditionally been a Solid geometry, three-dimensional solid, one of the most basic of curvilinear geometric shapes. In elementary geometry, it is considered a Prism (geometry), prism with a circle as its base. A cylinder may ...

surface in a firearm, usually creating grooves. This is most often the

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 ...

of a

rifle A rifle is a long gun, long-barreled firearm designed for accurate shooting and higher stopping power, with a gun barrel, barrel that has a helical or spiralling pattern of grooves (rifling) cut into the bore wall. In keeping with their focus o ...

, though it may also refer to the

cylinder A cylinder () has traditionally been a three-dimensional solid, one of the most basic of curvilinear geometric shapes. In elementary geometry, it is considered a prism with a circle as its base. A cylinder may also be defined as an infinite ...

of a

revolver A revolver is a repeating handgun with at least one barrel and a revolving cylinder containing multiple chambers (each holding a single cartridge) for firing. Because most revolver models hold six cartridges before needing to be reloaded, ...

or the bolt of a

bolt action Bolt action is a type of manual firearm action that is operated by ''directly'' manipulating the turn-bolt via a bolt handle, most commonly placed on the right-hand side of the firearm (as most users are right-handed). The majority of b ...

rifle. In contrast to rifle barrels and revolver cylinders, rifle bolts are normally helically fluted, though helical fluting is sometimes also applied to rifle barrels.

Purpose

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

surface area The surface area (symbol ''A'') of a solid object is a measure of the total area that the surface of the object occupies. The mathematical definition of surface area in the presence of curved surfaces is considerably more involved than the d ...

to make the barrels less susceptible for overheating for a given total weight. However, for a given

diameter In geometry, a diameter of a circle is any straight line segment that passes through the centre of the circle and whose endpoints lie on the circle. It can also be defined as the longest Chord (geometry), chord of the circle. Both definitions a ...

, while a fluted barrel may cool more quickly, a non-fluted barrel will be stiffer and be able to absorb a larger amount of total heat at the price of additional total weight.

In barrel chamber

In the barrel chamber, fluting refers to gas relief flutes/grooves used to ease the extraction of cartridges. They may also come in annular and helical forms.Krcma, V., "Fluted and Annular Grooved Barrel Chambers in Firearms," Journal of Forensic Sciences, JFSCA, Vol. 41, No. 3, May 1996, pp. 407-417. Notable firearms using fluted chambers are the roller-delayed blowback

Heckler & Koch G3 The Heckler & Koch G3 () is a selective fire, select-fire battle rifle chambered in 7.62×51mm NATO developed in the 1950s by the German firearms manufacturer Heckler & Koch, in collaboration with the Spanish state-owned firearms manufacturer CE ...

and lever-delayed blowback FAMAS and AA-52. Roller or lever-delayed blowback arms require that the bolt starts moving while the bullet is still in the barrel and the spent case is fully pressurized. Fluting the end of the chamber allows combustion gasses to float the neck and front of the cartridge case providing pressure equalization between the front outer surface of the cartridge case and its interior. The roller-delayed blowback StG 45(M) assault rifle prototypes proved pressure equalization fluting is desirable, since the breech of roller or lever-delayed blowback arms is opened whilst under very high internal cartridge case pressure that presses a spent (bloated) cartridge casing against the chamber walls which can cause significant problems during the cartridge extraction phase. Using traditionally cut (non-fluted) chambers in the StG 45(M) resulted in separated cartridge case heads during testing.

References

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External links

How to flute a rifle barrelThe Different Types of Barrel Contours and What You’re Left WithThe Real Benefits of Barrel Fluting
Firearm components

Purpose

In barrel chamber

See also

References

External links