The cutting of spiral grooves on the inside of the barrel of a firearm WordNet 3.0 & Open English WordNet

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. Wikipedia

Helical groovings in the internal surface of a firearm barrel Wikidata

Process of grooving a gun barrel to increase a projectile's range and accuracy Wikidata

The system of grooves in a rifled gun barrel or cannon. Shunt rifling, rifling for cannon, in which one side of the groove is made deeper than the other, to facilitate loading with shot having projections which enter by the deeper part of the grooves. Wiktionary

System of grooves. Wiktionary (translation)