Rev. Rul. 56-29, 1956-1 C.B. 552

      A tear gas gun designed to expel only a gas or mist, and not
capable of firing a shot or projectile, is not considered a firearm
under either the National or Federal Firearms Act.  If any such
device is capable of firing other than the shells or cartridges
designed for use therewith, such as fixed metallic cartridges or
shotgun shells, it is a fire arm within the purview of the National
and/or Federal Firearms Act depending upon the physical
characteristics of the individual weapon.

      Advice has been requested whether small caliber guns which
fire cartridges loaded with tear gas or a similar substance are
subject to the provisions of the Federal Firearms Act or the
National Firearms Act (Chapter 53 of the Internal Revenue Code of
1954).

      Section 1 of the Federal Firearms Act, 15 U.S.C. 901, defines
a firearm as "any weapon, by whatever name known, which is designed
to expel a projectile or projectiles by the action of an explosive
and a firearm muffler or firearm silencer, or any part or parts of
such weapon."

      Section 5848(1) of the Internal Revneue Code of 1954 defines
a firearm as "a shotgun or rifle having a barrel of less than 18
inches in length, 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, but does not
include any rifle which is within the foregoing provisions solely
by reason of the length of its barrel if the caliber of such rifle
is .22 or smaller and if its barrel is 16 inches or more in
length."

      The classification of a weapon within the category of a
firearm is dependent upon several conditions, as indicated in the
above definitions of a "firearm," and the physical examination of
the individual device is usually required to formulate a definite
opinion.  However, if a tear gas gun is designed to expel only a
gas or other mist rather than a shot or a projectile, such a device
is not classified as a firearm under either the National or Federal
Firearms Act.  If such a device is capable of firing other than the
shells or cartridges designed for use therewith, such as fixed
metallic cartridges or shotgun shells, it is a firearm within the
purview of the National and/or Federal Firearms Act, depending upon
the individual characteristics of the device.  For example, see
Revenue Ruling 55-529, C.B. 1955-2, 482, which classifies two
weapons, designed to expel a gas mist but chambered to accommodate
fixed shotgun shells or pistol or revolver ammunition, as firearms.

  Rev. Rul. 56-29