Rifle, firearm with a rifled caliber, that is, with shallow spiral grooves carved into the barrel to impart rotation to the bullet, stabilizing it in flight. A rifled barrel gives much greater accuracy to a bullet than a smooth barrel. The name rifle, most often applied to a shoulder weapon, can also denote a weapon served by the crew, such as a rifled barrel or recoilless rifle. Although field guns, pistols and machine guns have rifled barrels, they are not normally referred to as rifles.
Fluted firearms date back to at least the 15th century. Since some of the earliest ones had straight grooves rather than spirals, it is believed that the initial purpose may have been to receive the residue of dust, or scale, which was a problem with early firearms. However, gun manufacturers soon discovered that the spiral flutes made the bullets spin and that rotation improved their range and accuracy. The effect increased when the spherical balls were replaced by slightly elongated bullets.
In early muzzle-loading rifles, guiding the bullet through the hole was difficult, as the bullet had to adapt well to the rifling. Such rifles could not be loaded as fast as smoothbore muskets. This problem was solved first by using oiled patches around the bullet. Later, and much better, he was approached by the Minié ball, a bullet with a conical head and hollow base that was slightly expanded by the force of the propellant charge, thus adapting firmly to the grooves of the rifling. A little later, the invention of metal cartridges (combining the explosive primer, propellant and projectile in a self-contained unit) allowed the development of gas-tight breech loading mechanisms. The technology was first applied in the 19th century to lever, rotary cylinder, and single-stroke repeater arms. Many breech-loading rifles that found widespread use in the early 1900s, such as Springfield, Enfield, and Mauser, were bolt-action military weapons. However, since World War II, the assault rifle, a light medium-range weapon with a switch that allows for semi-automatic or fully automatic fire, has become the dominant military rifle.
Repeating rifles similar to 20th century military weapons are still the most common type of hunting. The bolt action is efficient, reliable and easy to manufacture and maintain. Most of these guns have boxed magazines for storing cartridges and quickly reloading after each shot. Lever-action and slide-action or pump action shotguns are used less frequently in the 21st century, but after World War II semi-automatic shotguns became popular for hunting in the United States. In some countries it is illegal to hunt with a semi-automatic rifle.