From what I have read and heard most are from straw sales or private sales to know felons. I.E. ghetto rat goes to his buddy, buddy buys gun sells to felon for a mark up. The other I have heard is about the same, a guy buys a gun legally then sells it later to a felon wether he knows it or not. Then there is the whole gun show loophole. I for one would not object to a free background check at gun shows to make sure dirt bags are not buying my gun. I due my check I.D. ask for a CHL and ask if they are a felon, but how do you really know?