What’s the destructive device that he is accused of making?
A gun?
A smallpipe with a 12 ga shell in it. Poor mans claymore for perimeter protection.
He probably had some plumbing parts and ammo reloading supplies in his basement. This become “he was stockpiling materials for construction of pipe bombs” in the indictment to come.
Regarding the grand jury - an ambitious, competent prosecutor can get an indictment against a ham sandwich.
Sounds like he might have been making a perfectly legal device known as a "Slam-Bang Shotgun".
Also known as a "Philippine Guerrilla Gun" or a "Richardson Gun".
It's more or less a 12 Ga. Zip Gun.
The simple version is two pieces of steel water pipe and a pipe cap.
Instructions are all over the net - just Google the term.
Here is a video of one example:
$7 12-Gauge Zip Gun Homemade Shotgun
“What’s the destructive device that he is accused of making? A gun?”
The term “destructive device” is a legal term spelled out in an act of congress, not common parlance. It has a specific definition, it’s not just some bit of word soup that can refer to whatever in the hell people want it to mean at the moment; in this case the term refers to items specifically defined in the National Firearms Act of 1934. It’s not a term that can refer to any gun, or a dangerous idea you come up with.
Look up 26 U.S.C. § 5845 subsection (f).
http://www.law.cornell.edu/uscode/text/26/5845
As a general rule any time you see charges describing a destructive device the charges will likely be referring to pipe bombs and suchlike.
A note about the NFA — the act was drafted back when Congress actually thought it was kindof bound by the constitution, so the act doesn’t actually ban the devices mentioned, merely levies a tax upon them and requires some form of application/registration for the possession, transfer, or construction of said items. This act was drafted back before the FDR administration successfully gutted most restrictions on federal authority.
Some states do effectively ban some of the items regulated under the NFA, some don’t; consequently you’ll find that in some states people are legally playing around with federally registered and taxed things like 40mm HEDP and RPGs — rare but interesting.
In this case the individual in question is being charged with the untaxed construction/transfer/sale/whatever of, effectively, pipe bombs.