After Sandy Hook, CT passed new regulations with a window before they took effect. At that time, I had no interest in AR-15's or "high capacity" handguns. I bought (3) AR's, a G34, a couple of Sigs and a revolver I'd been eyeing. Broke a cardinal house rule and used a credit card. Came home, told my wife what I'd done, and what my plans were to pay off the debt and that was the end of that.
Moved down here, leaving the ARs in a safe in CT, and immediately bought one for the safe here. Started thinking as the rumblings about "assault weapons" grew on the national level, and bought some 80% lowers for AR's. While I was at it, I bought a couple 80% lowers compatible for Gen 3 G17s.
The majority of the firearms I own were built by "manufacturers", serialized and at some point went through distributor and FFL. I've got some from private sales that there's no paperwork on, (perfectly legal here), and I've got some lowers that never had serial numbers.
If you believe that there's any chance that the government, (local/state/federal), might demand that you relinquish the firearms that they know about, (the ones on a list) - then you should have some that they don't know about. And they should be stored somewhere other than where your listed ones are.
As for the OP - if you're smart enough to fly a plane - you're smart enough to finish out an 80% lower - there are about 152,375 [1] videos on youtube showing how to do it.
[1] Yes, I DID pull that number out of my ass - but there ARE plenty of videos out there.