Despite all of the propaganda from the left, every legally sold firearm in this country, even at gun shows, the buyer must go through a federal background check.
The database they keep of violent, unstable people is so horribly inaccurate and out of date. It is not maintained properly much like the no fly list. The reason why the government so absolutely sucks at everything it does is because there is no motivation to excel. If they mess up they just ask for more money and they get it. It never matters how much money is thrown at problems the government just keeps perpetuating the incompetence because they do not care. There are a few departments and agencies that are ran better than others but none of them have the slightest concern about fleecing the taxpayer.