3.10 Gauge

Lead balls on scale Shotguns are measured in gauge. For shotguns, gauge is the number of lead balls, each the diameter of the gun's bore, that it would take to weigh one pound. For example, if you have lead balls the same diameter as a 12-gauge shotgun bore, it will take 12 of those balls to make one pound.

How many 16-gauge lead balls would it take to make one pound? 20-gauge? 28-gauge?

As shown in the drawings at right, the larger the gauge number, the smaller the bore diameter. For example, a 20-gauge shotgun has a smaller bore diameter than a 10-gauge shotgun. It takes more balls, of a smaller size, to equal one pound.

The .410 is the only exception to the way in which shotguns are measured. Look carefully at how this number is written. It is actually a caliber because it has a decimal point (.) in front of the number! The .410—if measured in gauge—would really be about a 67 gauge!

Data stamps on gun barrels showing gauge and caliber designations

Be sure that your shotshells match the gauge of your firearm! Never carry shotshells unless you check the gauge first! Never shoot ammunition that does not exactly match your shotgun! Shotshells come in different lengths. You may safely fire a shorter length shell than the indicated length of the chamber of your shotgun. For example, a 2-3/4 inch shotshell will work in a 3-1/2 inch chamber. Do NOT put a 3-inch shotshell into a 2-3/4 inch chamber!

Finding the Correct Ammunition for Your Shotgun

To find the correct gauge and shell length, look on the side of the shotgun barrel. Generally, you will find the gauge and chamber length stamped on the barrel. This is true for all new firearms, but older firearms and custom firearms may not have such markings. Make sure you check the gauge and shell length of your gun before you shoot it and use only the correct ammunition! If you are unsure of the gauge or chamber length of your shotgun, take it to a gunsmith to check.

Shotshells almost always have the gauge stamped on the base. Information on shotshell case length is found on the shotshell box.

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Washington Hunting
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Official hunting safety course for Washington hunters last modified: May 9, 2008
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