A pen gun is a firearm that resembles an ink pen.[1][2] They generally are of small caliber (e.g., .22 LR, .25 ACP, .32 ACP, .38-caliber, etc.)[3][4][5] and are single shot.[4][6] Early examples of pen guns were pinfired, but modern designs are rim or centerfire.[1] Some pen guns are not designed to fire regular cartridges, but rather blank cartridges, signal flares, or tear gas cartridges.[1][7]
In the United States, pen guns that can fire bullet or shot cartridges and do not require a reconfiguration to fire (e.g., folding to the shape of a pistol) are federally regulated as an Any Other Weapon (Title II). They require registration under the National Firearms Act and a tax in the amount of five dollars is levied.[7][8]
According to the FBI, pen guns were widely used for self-defense in the 20th century.[9]
