Okay, so if you've ever bought any firearms through a dealer, then should the government find it necessary to come a looking, they already have a record that you own or have owned firearms, so you go on the check anyways list. Now if they come and they find you have a firearm(s) they don't know about, especially one that may have an adverse history, now the trouble starts. If they decide even just one of the guns in your collection is a bad apple, they will likely take the whole bunch, followed by a search warrant on the rest of your house, and finally cuffed and stuffed.
Unless your entire gun collection is off the books AND you have managed to keep your mouth shut about it all this time, I would say that buying as a private sale, especially from someone without a bona-fides, is just asking to be labeled a suspect.
I don;t think they would do that Benjamin, and here's why I say:
- I work with ATF guys and local police and they're as hard-core a gun owner as anyone else I know;
- They have no idea what guns I own unless they're investigating me for an offense that permits them to dig through archived records, and even then, it's like looking for a needle in.....;
- There is no requirement to "register" a firearm, unless it's an automatic or otherwise prohibited without license;
- private sales are done everyday (i.e. you're over for dinner at my house and you like this gun I have. You ask if it's for sale and I say yes. Done.);
- certain States and cities may have "registry" laws, but that would apply whether you bought the gun public or private;
- the only item that can be seized is one that's already illegal to obtain, or was obtained as fruit of a crime, or one that's stolen, or one that's been used in a crime. So.... if the police had a reason to look for, find, and seize the hypothetical weapon, they would have no legal justification to seize the others (now, law can be complicated, but this inability of theirs to seize the "other" weapons you own is under the assumption that there's been no other crime);
- in then end, about the only things a buyer has to worry about are:
...- whether the weapon is functional;
...- whether or not it's stolen;
...- whether or not it's been used in a crime.
I really don;t think it's much of an issue if a few precautions are taken.