What is a key feature of a firearm barrel that enables bullet spin?

The key feature of a firearm barrel that enables a bullet to spin is known as rifling. Rifling consists of helical grooves cut or formed into the barrel's interior. These grooves grip the bullet as it is fired, causing it to spin rapidly along its axis. This spin stabilizes the bullet in flight, making it more accurate over longer distances.

The design of rifling plays an essential role in the performance of a firearm by enhancing projectile stability, which is crucial for precision shooting. Without rifling, bullets would tend to tumble in flight, leading to decreased accuracy and effectiveness.

Understanding rifling is fundamental for anyone interested in firearms, as it not only impacts the performance of the bullet but also informs the choice of ammunition for specific types of firearms.