What is the maximum barrel length for a shotgun to be considered a short-barrel firearm?

To understand the classification of shotguns as short-barrel firearms, it is essential to look at regulations established by federal law. Under the National Firearms Act (NFA), a shotgun is categorized as a short-barreled shotgun (SBS) if its barrel length is less than 18 inches. Consequently, the maximum barrel length for a shotgun to still be legally categorized as a short-barrel firearm is indeed 18 inches. This definition is crucial for determining the legal requirements surrounding the ownership and regulation of firearms, particularly in law enforcement and public safety contexts.

In the context of the options provided, lengths shorter than 18 inches would classify as a short-barreled shotgun, while any length greater than or equal to 18 inches would not. This understanding helps to ensure compliance with laws regulating firearm possession and use.