Depending on the state (I guess), private sellers are allowed their own booths at gun shows and only dealers are required to do background checks (this is part of the "gun show loop hole"). But private sellers at gun shows make up a small percent, mostly just collectors. There would be no profit to buy a gun and then try to sell it as a private sell at a gun show. "Gun people" are not stupid and the last thing that would be allowed at a gun show would be someone posing as a private seller and selling marked up firearms to people that would otherwise refuse to pay a lower price from a dealer but would have to do a background check with them....
Requiring background checks for private gun sales sounds like a good idea until you do the research on the effort vs benefit. The effort to enforce this would be massive and virtually no gun crimes are committed with these guns anyways. In practical terms you'd have to track every firearm and figure out what to do when Grandpa does and leaves his gun to his children. A parent would have to run a background check on their own child of they buy a gun for them as a gift. Realistically, the only time it could be determined that a gun was sold in private without a background check is if the gun is eventually used in a crime and recovered. The vast, vast majority of guns that wind up in the hands of criminals are through corrupt licensed dealers and straw purchases.
If the purpose of gun control laws is to prevent violent crime, then there's no loophole here since this is not a significant source of weapons used in violent crimes.
Your argument that it is silly hinges on the idea that parents wouldn't ever do that. But they would.
Those background checks in total would have little impact, but it's not a good argument against requiring background checks.
Private people can have stock at gun shows and not be required to have a Federal Firearm License.
I'll put a link here, not that you'll check it.
http://www.governing.com/gov-data/safety-justice/gun-show-fi...
Yes, a private individual could liquidate their closet of guns they don't want anymore at a gun show without being legally required to conduct a background check. They can't have "stock" or "inventory" or otherwise resemble any attempt to be in the business of selling firearms or they're going to get a nasty visit from BATFE.
The Ghost Gunner machine mentioned in the article is actually a CNC mill using 7075 billet aluminum blocks.