Rev. Rul. 56-94

The Internal Revenue Service has examined and test-fired a six-shot, .22 caliber, alarm-starter revolver, designed to fire blanks which are inserted through a loading gate near the right rear side of the cylinder. The front of each chamber in the cylinder is constricted to such a degree that commercial .22 caliber fixed ammunition cannot be used; and, in addition, the breech end of the barrel is constricted while the bore is approximately 1/4 inch in diameter at the muzzle. The explosion of the blank ammunition is released through a small opening in the front of the chamber and expelled from the muzzle of the barrel which is threaded on the inside so that a signal flare can be inserted and fired. By the same principle, it was found that a lead bullet, when loaded through the muzzle, could be fired to a distance of 75 feet. Held, any pistol or revolver ostensibly designed to fire blank ammunition but capable of expelling a projectile or projectiles by the action of an explosive is a firearm within the purview of the Federal Firearms Act, and is subject to the regulatory provisions thereof.