Measuring gauge and measuring caliber are two different methods used to describe the size of firearms and ammunition. Here's an explanation of each:
Gauge: Gauge is a measurement used specifically for shotguns. It represents the number of lead balls with the same diameter as the gun's bore that would equal one pound in weight. The gauge number is inversely related to the size of the shotgun bore. For example, a 12-gauge shotgun has a larger bore diameter than a 20-gauge shotgun. The larger the gauge number, the smaller the diameter of the barrel.
Caliber: Caliber is a measurement used to describe the internal diameter of a firearm barrel or the diameter of a bullet or cartridge. It is most commonly used for handguns, rifles, and some types of ammunition. Caliber is typically expressed in decimal inches or millimeters. For example, .45 ACP (Automatic Colt Pistol) refers to a bullet diameter of .45 inches, while 9mm Luger represents a bullet diameter of 9mm.
The key difference between gauge and caliber is the type of firearms they are used to describe. Gauge is specific to shotguns, while caliber is used for handguns, rifles, and some types of ammunition.
It's important to note that gauge and caliber are not directly interchangeable. They represent different measurement systems for different types of firearms. So, a 12-gauge shotgun does not have a caliber equivalent, and a .45 caliber handgun does not have a gauge equivalent.
When selecting firearms or ammunition, it's essential to use the appropriate gauge or caliber designation based on the type of firearm being considered. Always refer to the manufacturer's specifications and recommendations for the correct gauge or caliber for a particular firearm.