owning an SBR

[UVvis]

Is constructive intent a real concept that people have gone to trial for?

If your intent is to build a Pistol AR, or a SBR by following NFA guidlines, I don't see why the ATF would have issues with anyone.

If you have a SBR and a regular 16" AR, then you would again have the parts needed to be in violation of the NFA.

[geminidglocker]

Yup, I own a pistol lower which I intend to build into a pistol first, to work out any bugs, then, when I SBR it, I can just pay the 200bucks and wait to replace the buffer tube to one that will accept a stock.