Rev. Rul. 59-341, 1959-2 C.B. 376

      The Internal Revenue Service has had the occasion to examine
the Dardick Handgun, a double-action, semiautomatic, revolving
cylinder weapon.  This weapon is basically a .38 caliber handgun,
employing a continuous feed system, and using a triangular shaped
cartridge case, the .38 Dardick "Trounds."  By means of an adapter
and an interchangeable .22 caliber barrel, conventional .22 caliber
ammunition can also be fired from the basic gun.  Ammunition cannot
be fired by the basic mechanism unless a barrel is attached.  By
inserting the basic mechanism into a one piece rifle unit, the gun
becomes a .22 caliber rifle with a barrel length of over 16 inches.

      Held, the Dardick Handgun is not a firearm within the purview
of the National Firearms Act (chapter 53 of the Internal Revenue
Code of 1954); however, it is subject to the Federal Firearms Act
(15 U.S.C. 901).

  Rev. Rul. 59-341