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. It is also the term for creating such grooves.
Conventional rifling of a 90 mm M75 cannon (production year 1891, Austria-Hungary)
Rifling of a 105 mm Royal Ordnance L7 tank gun
Rifling in a GAU-8 autocannon
Traditional rifling of a 9 mm handgun barrel
A firearm is any type of gun that uses an explosive charge and is designed to be readily carried and used by an individual. The term is legally defined further in different countries.
The Colt Single Action Army, a revolver chambered in .45 Colt
The Glock 19, a pistol chambered in 9×19mm Parabellum
The Mosin–Nagant, a rifle chambered in 7.62×54mmR
The M4 carbine, a carbine derivative of the M16 rifle, chambered in 5.56×45mm NATO