Kalibers

Caliber, or calibre, is a measure of the internal diameter of a gun's bore, and by extension the diameter of the bullet that the gun fires. It is a core concept in firearms design and ballistics. Caliber is usually expressed in either inches or millimeters. In the United States, pistol and rifle calibers are commonly written as a decimal inch value (for example, .45, .22, .30) or as a full cartridge designation that includes the caliber, such as .30-06 Springfield or .308 Winchester. In many parts of the world, calibers are stated in millimeters (for example, 9 mm, 7.62 mm, 5.56 mm). The nominal diameter typically refers to the bore, while the actual bullet diameter is usually a few thousandths of an inch smaller to ensure proper seating and accuracy.

Cartridges are often named to reflect caliber, but the naming conventions are varied: some names indicate bullet diameter, others reflect case length or historical factors. The same caliber can support multiple cartridges with different case designs, pressures, and performance. The term also crosses into shotguns, where gauges, rather than calibers, describe bore size; a smaller gauge means a larger bore.

In practice, caliber affects recoil, velocity, expansion behavior, and penetration, and it interacts with bullet weight, powder charge, barrel length, and rifling. Caliber choice influences firearm selection, ammunition availability, and regulatory considerations.