About to start my sbr build in 300 blk..

[Theohazard]

Fair enough. But previously you said this;

[You] can't have a "spare" pistol upper and an AR in the same house.

I would not keep a pistol upper and any unregistered AR in the same house.

In those statements it seemed that you were claiming it's illegal to have a short upper and an AR lower in the same house, which is not necessarily true.

The area of ONLY owning nonSBR rifles AND a pistol upper is what can potentially get you into trouble.

Agreed. If you own the parts to make an illegal SBR and you don't have other parts that would give you a "useful purpose" for having them (a registered SBR lower or a pistol lower), then you could get in trouble if those parts are in "close proximity" to each other. But like both of us have indicated already, "close proximity" is a subjective term.

 

[9x19]

I have a stripped lower still sitting in the box.

When I decided to go SBR, I didn't want to worry over the above, so for $45 (cost of the lower) I could now buy and have a short upper in the house while waiting for that first stamp.

I did it because sales on uppers happen faster than the ATF processes form 1s.