What does barrel harmonics measure in a firearm?

Barrel harmonics refers to the study of how a firearm's barrel vibrates when a shot is fired. When a bullet is expelled from the chamber and down the barrel, it generates vibrations and oscillations due to the rapid pressure change and the acceleration of the bullet. The ability of the barrel to return to its original position after these vibrations are generated is critical for achieving consistent accuracy.

When a barrel vibrates, it may oscillate in various directions. The point at which the bullet exits the barrel can be affected by this oscillation. If the barrel can return to a consistent position (true) after firing, then the path of the bullet will be more predictable, leading to improved accuracy. Therefore, the correct answer is closely tied to the understanding of how a barrel's physical dynamics affect shot precision.

Understanding barrel harmonics is an essential part of accurate shooting and tuning a firearm for optimal performance. It involves not just the material or length of the barrel but focuses on how well the barrel can 'remember' its intended alignment after the shot has been fired.