Under the National Firearms Act of 1934, firearms with shoulder stocks or originally manufactured as a rifle and barrels less than in length are classified as short-barreled rifles. Short-barreled rifles are restricted similarly to short-barreled shotguns, requiring a $200 tax paid prior to manufacture or transfer – a process which can take several months. Because of this, firearms with barrels of less than and a shoulder stock are uncommon. A list of firearms not covered by the NFA due to their antique status may be found here or due to their "Curio and Relic" status may be found here; these lists includes a number of carbines with barrels less than the minimum legal length and firearms that are "primarily collector's items and are not likely to be used as weapons and, therefore, are excluded from the provisions of the National Firearms Act." Machine guns, as their own class of firearm, are not subject to requirements of other class firearms.