Seems you're right mostly.
Apparently there was a court case and ATF ruling dealing with SBR's, pistols, and specifically Thompson Center contender/encore's
If I understand it right constructive possession here requires the items assembled items to be in "close proximity".
But what is close proximity? same container? arms reach? same room? same building?
The link you posted the guy likely lost the case (although did'nt see any update on the outcome) because he was selling the items as a set, the case cut out seems to suggest the gun may have been configured with the vertical grip at some point.
If he had also had a 16inch barrel in the kit he was selling he likely would have been fine.
From what I understand.
Rifle > Pistol = NFA
Pistol > Rifle = OK, > back to pistol = OK
This is why you sometimes see people on you tube video them selves building (stripped lower) AR-15's into pistols first before re-configuring them into rifles, easily done except you need access to a shorter then 16inch upper which could be a problem if you're not planing on keeping one in pistol configuration.. Apparently bare receivers are considered a pistol or rifle depending on it's first configuration.
How the factory shipped the gun is what counts.
Bare receivers, pistols, and "carbine" kits are ok, But rifles are always rifles.
The real gray area here is the "close proximity"
A firearm, as defined by the National Firearms Act (NFA), 26 U.S.C. 5845(a)(3), is
made when unassembled parts are placed in close proximity in such a way that they: (a)
serve no useful purpose other than to make a rifle having a barrel or barrels of less than
16 inches in length; or (b) convert a complete weapon into such an NFA firearm
Since "close" is a relative term, Having a ar-15 "rifle" AND a shorter then 16inch upper merely in your possession does not seem to be out right forbidden.
I would think CW's plan to take ar-15 "rifles" to his brothers would satisfy any definition of "close" but who knows.http://www.bellmtcs.com/store/index.php?cid=239http://www.atf.gov/files/regulations-ru ... 2011-4.pdf