Gauge

The use of gauge when referring to shotguns

Gauge refers to the number of lead balls that it would take to make one pound (1 lb) of that size of ball. For example, it would take 10 x (“10 gauge diameter” lead balls) to equal 1 lb. It’d take 12 x (“12 gauge diameter” lead balls) to equal 1 lb. Since 10 < 12, you have less balls when you use a 10 gauge, but each one is bigger (now if that isn’t a statement on life, I don’t know what is).

Note: a .410 shotgun refers to bore diameter, and not gauge.