A shotgun's gauge is based on the gauge of a smoothbore musket. This was defined on the number of lead balls fitting the barrel that would weigh 1 pound.


The density of lead is 11.35 g per cubic cm.

1 pound of shot weighs 453.6 grams.


radius of spherical shot fitting the barrel =

= (diameter of the barrel in cm) / 2


volume of the shot in cubic cm =

= 4 * PI() / 3 * ((radius in cm)^3)


weight of the shot =

= (volume in cubic cm) * 11.35


shotgun gauge =

= ROUND(453.6/(weight of shot in grams)


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