What causes bullets to spin when shot from a rifle or handgun?

Bullets spin when fired from a rifle or handgun due to the presence of rifling inside the barrel of the firearm. Rifling consists of helical grooves cut into the inside of the barrel, which imparts a gyroscopic effect on the bullet as it moves through the barrel. This spinning motion stabilizes the bullet in flight, allowing it to maintain a straighter and more accurate trajectory over longer distances.

The rifling causes the bullet to rotate around its axis, which is critical for accuracy because a spinning bullet is less affected by external forces such as wind and gravitational drop. This stability helps ensure that the bullet retains its intended path toward the target, making rifling an essential feature of most modern firearms for enhanced performance.

Other factors, such as wind resistance, gravity, and bullet design, can influence a bullet's flight after it leaves the barrel, but they do not contribute to the initial spinning motion imparted to the bullet during firing.