Page "Carbine" Paragraph 43

Another class of carbine is a semi-automatic version of a submachine gun, with an extended barrel, usually just over 406 mm ( 16 inches ) long, which will escape ban by some " assault weapon " legislation.

While functionally identical to pistol-caliber carbines, these are banned in some places as " assault weapons " based on their cosmetic similarity to submachine guns.

However, they may not accept certain parts ( such as magazines or collapsing stocks ) from the submachine guns they resemble.

These are a popular compromise for ( American ) shooters who would like to own a submachine gun but cannot due to local restrictions or the prohibitive cost of buying a civilian legal submachine gun ( full automatics or semi-automatics with barrels shorter than are restricted under Title II of the National Firearms Act ).

Many owners may choose to shorten the barrels down to NFA-lengths, and register them as " short barrel rifles " SBRs.