I've heard this myth before. I think this is because it is confused with a specific ruling from the ATF regarding 37/38mm launchers when possessed with its ammunition. Here is the text of the letter:
The definition of “destructive device” in the GCA (18 U.S.C. § 921(a)(4)) is identical to that in the NFA. ATF has previously held that devices designed for expelling tear gas or pyrotechnic signals are not weapons and are exempt from the destructive device definition. However, ammunition designed to be used against individuals is available for these 37/38 mm devices. This “antipersonnel” ammunition consists of cartridges containing wood pellets, rubber pellets or balls, and bean bags. When a gas/flare gun is possessed with “anti-personnel” type ammunition, it clearly becomes an instrument of offensive or defensive combat and is capable of use as a weapon. Since these gas/flare guns have a bore diameter of greater than one-half inch, fire a projectile by the means of an explosive, and, when possessed with “anti-personnel” ammunition, are capable of use as weapons, the combination of the gas/flare gun and “anti-personnel” ammunition is a destructive device as defined in the GCA and NFA. As a result, registration as a destructive device is required. Any person possessing a gas/flare gun with which “anti-personnel” ammunition will be used must register the making of a destructive device prior to the acquisition of any “antipersonnel” ammunition. In addition, the gas/flare guns are classified as firearms as defined by the GCA when possessed with “anti-personnel” type ammunition.
Here is verbiage of the NFA:
Firearms Verification
National Firearms Act Definitions
Destructive Device
26 U.S.C. § 5845(F)
For the purposes of the National Firearms Act, the term “Destructive Device” means:
- A missile having an explosive or incendiary charge of more than 1/4 oz.
- Any type of weapon by whatever name known which will, or which may readily be converted to expel a projectile, by the action of an explosive or other propellant, the barrel or barrels of which have a bore greater than one-half inch in diameter.
- A combination of parts designed and intended for use in converting a device into a destructive device and from which a destructive device can be readily assembled.
Exemptions:
- A shotgun or shotgun shell which is determined by the Attorney General to be generally recognized as particularly suitable for sporting purposes.
- a device which is neither designed nor redesigned for use as a weapon,
- a device which is designed or redesigned for use as a signaling, pyrotechnic, line-throwing, safety, or similar device,
- surplus ordnance sold, loaded, or given by the Secretary of the Army pursuant to law such as antique, obsolete bronze or iron cannon,
- a device which the Attorney General determines is not likely to be used as a weapon.
- An antique firearm, or
- a rifle which the owner intended to use solely for sporting purposes.