What does the caliber of a pistol mean?

Caliber is the term used to describe the diameter of the bore in a firearm, usually expressed in inches or millimeters. It can also be used to collectively refer to the bore diameter, the cartridge type the firearm is designed to use, and the overall performance and capabilities of the firearm.

In the context of pistols, the caliber often indicates the diameter of the bullet fired from the gun, which is typically expressed as a decimal measurement in inches. For example, a ".45 caliber" pistol fires bullets that have a diameter of 0.45 inches. Some common pistol calibers include 9mm (9 millimeters), .40 S&W (.40 Smith and Wesson), .45 ACP (.45 Automatic Colt Pistol), and .380 ACP (.380 Automatic Colt Pistol).

Understanding caliber is crucial when choosing ammunition and firearms, ensuring the correct cartridges are used for a specific gun. Pistols with different calibers may have varying properties and performance characteristics, including bullet size, muzzle velocity, stopping power, recoil, and effective range.