Caliber of a Handgun or Rifle

Last Updated on May 13, 2023 by Dwayne Easton

The term caliber refers to the bore size of a rifle, handgun or shotgun. It also describes the cartridges that are designed for different bores.

  • The diameter of the bore measured from one land to the other is called caliber. It is usually expressed in millimeters, thousandsths of an inches, or hundredths. A.270 rifle bore is 270/1000ths inch in diameter. It has a smaller bore diameter than a rifle of the same calibre. There is no standard for identifying caliber. The caliber can be defined as the bullet’s diameter, or the distance between the grooves.
  • Sometimes, caliber designations have a second number that is not related to the diameter. The popular.30-30 cartridge is a.30 caliber cartridge. However, the second number is a remnant from when the cartridge used 30 grains of powder. The year it was officially adopted by the U.S. Military is indicated by the “06” in the.30-06 cartridge.
  • Each rifle and handgun is made for a particular cartridge. The firearm’s barrel stamp must match the ammunition.
  • Different cartridges can be interchangeable even though they share the same bore. There are several.30 caliber firearms that have the same bullet size, but they are made for different cartridges. You can find the caliber stamped on your firearm by asking a gunsmith.
bullet sizes
The circles show bore sizes of common calibers.