Revenue Ruling 61-203

       A hand gun of the Luger or semi-automatic Mauser type, as
     well as the Fiala Arms and Equipment Company, Inc., .22
     caliber pistol, with a barrel of less than 16 inches in length
     is a "firearm," if it has an attached or attachable shoulder
     stock.
       However, where a hand gun of this type has a barrel of 16
     inches or more in length, it is not a "firearm" even though
     such weapon has an attached or attachable shoulder stock.

     Advice has been requested, whether semi-automatic hand guns,
such as Luger and Mauser pistols, and single shot .22 caliber
pistols made by the Fiala Arms and Equipment Company, Inc., with
attached or attachable shoulder stocks are "firearms" as defined in
section 5848(1) of the National Firearms Act (Chapter 53 of the
Internal Revenue Code of 1954).
     Basically such types of weapons were originally designed as
pistols.  However, they are also designed to function as rifles
which shoulder stocks are attached.
     Section 5848(1) of the National Firearms Act defines the term
"firearm" as follows:

     The term "firearm" means a shotgun having a barrel or barrels
     of less than 18 inches in length, or a rifle having a barrel
     or barrels of less than 16 inches in length, or any weapon
     made from a rifle or shotgun (whether by alteration,
     modification, or otherwise) if such weapon as modified has an
     overall length of less than 26 inches, or any other weapon,
     except a pistol or revolver, from which a shot is discharged
     by an explosive if such weapon is capable of being concealed
     on the person, or a machine gun, and includes a muffler or
     silencer for any firearm whether or not such firearm is
     included within the foregoing definition.

     Accordingly, a handgun of the Luger or semi-automatic Mauser
type, as well as the Fiala Arms and Equipment Company, Inc., .22
caliber pistol, with a barrel of less than 16 inches in length, is
held to be a "firearm," as that term is defined in section 5848(1)
of the Act, if such weapon has an attached or attachable shoulder
stock.  See also Rev. Rul. 61-45, C.B. 1961-1, 663.
     Conversely, where one of the above described pistols has a
barrel of 16 inches or more in length, it is held not to be a
"firearm," within the definition of 5848(1) of the Act, even though
such weapon has an attached or attachable shoulder stock.  With the
shoulder stock attached such weapon is a rifle.  When the shoulder
stock is detached, such weapon is a pistol, and is deemed not to
have been made from a rifle.
     On the other hand, certain types of weapons are not designed
to function as pistols.  This category includes semi-automatic
weapons with folding shoulder stocks such as the U. S. Carbine,
caliber .30, model MIAI, and the Marble Game Getter Gun.  These
weapons were originally designed to fire from the shoulder.
     Therefore, any such weapon with a folding shoulder stock is
held not to be a "firearm," as that term is defined in section
5848(1) of the Act, if it has either a rifled barrel of 16 inches
or more in length or a combination of a rifled and smooth bore
barrels of 18 inches or more in length.  However, if the shoulder
stock is removed from such a weapon it will be classified as a
"firearm," as that terms is defined in section 5848(1) of the Act,
if its overall length is less than 26 inches.