The term BB originated from the nomenclature of the size of steel shots used in a shotgun. Size "BB" shots were normally 0.180 in (4.6 mm), but tended to vary considerably in size due to the loose tolerances in shotgun shells. The highest size shotgun pellet commonly used was named OO or double ought and was used for hunting deer and thus called buckshot, while the smaller BB-sized shot was typically used to shoot small/medium-sized birds and therefore was a birdshot.
 
"cosmic"The term BB originated from the nomenclature of the size of steel shots used in a shotgun. Size "BB" shots were normally 0.180 in (4.6 mm), but tended to vary considerably in size due to the loose tolerances in shotgun shells. The highest size shotgun pellet commonly used was named OO or double ought and was used for hunting deer and thus called buckshot, while the smaller BB-sized shot was typically used to shoot small/medium-sized birds and therefore was a birdshot.
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