How is the caliber of a rifle or handgun determined?

The caliber of a rifle or handgun is defined by the diameter of the bore, which is the space between the opposite lands inside the barrel. This measurement is crucial because it directly relates to the size of the bullet that the firearm can effectively fire. When manufacturers specify the caliber, they typically refer to the diameter in either inches or millimeters, which indicates the bullet's size and, consequently, its potential power and performance.

Other factors, such as the length of the barrel or the weight of the bullet, do affect the firearm's overall function and performance, but they do not define the caliber. The length of the cartridge is also important for understanding ammunition compatibility, but it does not pertain to the caliber itself. Understanding caliber is essential for ensuring that the correct ammunition is used, which contributes to safe and effective shooting practices.