Editing Caliber (section)

==Shotguns==
{{Main|Gauge (firearms)}}

Shotguns are classed according to gauge, a related expression.  The gauge of a shotgun refers to how many lead spheres, each with a diameter equal to that of the bore, that amounts to one pound (454 g (1.0&nbsp;lb)) in weight. In the case of a 12-gauge (18.5&nbsp;mm) shotgun, it would take 12 spheres the size of the shotgun's bore to equal a pound.<ref name=Barnes2016-p629>{{Cite book |last=Barnes |first=Frank C. |editor-last=Woodard |editor-first=W. Todd |year=2016 |title=Cartridges of the World: A Complete and Illustrated Reference for More than 1500 Cartridges |edition=15th |location=Iola, Wis. |publisher=Krause Publications |isbn=978-1440246425 |oclc=934886116 |page=629}}</ref> A numerically larger gauge indicates a smaller barrel: a [[20-gauge]] (15.6&nbsp;mm) shotgun requires more spheres to equal a pound; therefore, its barrel is smaller than the 12-gauge. This metric is used in Russia as "caliber number": e.g., "shotgun of the 12 caliber." The 16th caliber is known as "lordly" ({{langx|ru|барский}}). While shotgun bores can be expressed in calibers (the [[.410 bore]] shotgun is measured as {{convert|.410|in|mm|abbr=on}} in diameter,<ref name=Barnes2016-p629/> unlike with rifles the actual bore diameter of a smoothbore shotgun varies significantly down the length of the barrel, with the use of [[Choke (firearms)|chokes]] and back-boring.

In the United Kingdom, "gauge" is referred to as "bore" and in the United States "bore" is referred to as "gauge", e.g. a "12-bore shotgun or 12-gauge shotgun" has a bore or gauge that can accommodate a lead sphere weighing 1/12th of a pound.