What is the barrel length requirement for a shotgun to be classified as a short barreled shotgun?

A shotgun is classified as a short barreled shotgun (SBS) if its barrel length is less than 18 inches. This definition is established in firearms regulations, particularly under the National Firearms Act (NFA) in the United States, where measurements of firearm barrels are specified for classification purposes. The limit of 18 inches ensures that firearms with shorter barrels are subject to stricter regulations due to their concealability and potential for use in criminal activity.

The other options reflect lengths that do not meet the legal definition for a short barreled shotgun, and thus, they are not applicable under current firearm legislation. The choice of 18 inches is significant as it provides a clear threshold that helps in regulating firearms effectively while considering aspects of safety and law enforcement.