When an ATF agent with a list of every “it’s not registration” 4473 form you’ve ever signed and sales records for every 80% lower you’ve ever bought shows up at your door, tell him that. I’m sure there will be belly laughs all around and he’ll leave, never to bother you again.
So you are just going to surrender them? Pussy.
You get their names, and have your friends visit their homes. It is just as legal.
Just tell BATFE the truth - that you sold them in a private sale and have no receipts. It’s legal & cannot be disproved - like stealing elections.