What term describes the size of a rifle or handgun bore, as well as the size of cartridges used with different bores?

The term that defines the size of a rifle or handgun bore, as well as the size of cartridges made for those bores, is "caliber." Caliber is a crucial measurement in firearms and ammunition, referring to the internal diameter of the barrel or the diameter of the projectile (bullet) itself. It is commonly expressed in either inches (e.g., .45 caliber) or millimeters (e.g., 9mm).

Understanding caliber is essential for hunters and shooters, as it affects factors such as accuracy, range, and stopping power of the ammunition. Each caliber has a specific type of ammunition that is designed to fit the bore of the firearm, which ensures proper function and safety. For instance, using the wrong caliber can lead to malfunctions or dangerous situations.

Gauge, on the other hand, specifically applies to shotguns and measures the bore size based on the number of lead balls of that diameter that weigh a pound. Shot charge refers to the amount of shot contained in a shotgun shell, and action refers to the mechanism of a firearm that facilitates firing, feeding, and ejecting cartridges. These terms, while related to firearms, do not encompass the direct measurement of bore size and cartridge compatibility in the same way that caliber does.