Last modified on June 29, 2016, at 03:57

Bore Diameter

Bore Diameter is the diameter of the barrel of any given firearm, through typically used to measure shotguns. Firearms other than shotguns, are measured in term of caliber.

According to Chuck Hawks, "Shotgun gauges are determined by the number of lead balls of a given diameter required to make one pound of that size ball. Thus 10 balls of 10 gauge diameter are required to make one pound of such balls, or 20 balls of 20 gauge diameter are required to make one pound, and so forth. This is the traditional, and very old, system."[1]

Popular gauges

Shotguns come in many sizes, typically measured by its gauge, or bore diameter. The most common shotgun size is 12 gauge and 20 gauge. Prior to 1950, there were many types of shotgun sizes in addition to the 12 and 20 including 4, 6, 8, 10, 13, 14, 16, 24, 28, 32, 36, 40, and 67.62 (This is the .410 gauge size, but measured the same one the others are, it would be 67.62).

"By the 1950's, according to Jack O'Connor in his The Shotgun Book, the 12 gauge had about 50% of the market. By the 1970's, again according to Jack O'Connor, the sales of 12 gauge guns and shells had declined somewhat to less than 50% of the market. The 20 gauge had taken over second place with about 20% of the market, and was still increasing its market share."[2]

Note that the larger the number, the smaller the size. The .410 is named for its nominal bore size, and is not a gauge at all.

See also

External links


  1. Introduction to Shotgun Gauges & Shells
  2. Ibid.