Another point I wanted to make since pete there got me stirred up. Okay, maybe more than one.
In the event the Federal Government filed charges (even if they don't) one could still be charged at the state level for the same offense (double jeopardy doesn’t apply state vs fed)
I have taken the liberty of providing excerpts from the Texas Penal Code, which shows this device is already illegal in Texas (which means what “everyone” thinks is a moot point).
§ 46.01. Definitions
In this chapter:
(16) "Zip gun" means a device or combination of devices that was not originally a firearm and is adapted to expel a projectile through a smooth-bore or rifled-bore barrel by using the energy generated by an explosion or burning substance.
§ 46.05. Prohibited Weapons
(a) A person commits an offense if he intentionally or knowingly possesses, manufactures, transports, repairs, or sells:
(1) an explosive weapon;
(2) a machine gun;
(3) a short-barrel firearm;
(4) a firearm silencer;
(5) a switchblade knife;
(6) knuckles;
(7) armor-piercing ammunition;
(8) a chemical dispensing device; or
(9) a zip gun.
e) An offense under this section is a felony of the third degree unless it is committed under Subsection (a)(5) or (a)(6), in which event, it is a Class A misdemeanor.
http://www.capitol.state.tx.us/statutes/pe/pe0004600.html#pe007.46.05
So ya see, this why I do not think it is illegal......I know it is.
Have a nice day.
Dave