Some anti-2nd amendment folk think that there are vast numbers of firearms being "sold" without background checks. They think that there are no checks at gun shows. They are so wrong. Most sales at gun shows are from FFL dealers. My experience at gun shows is that the sales of private firearms are TO FFL dealers. It is rare for a sale from private citizen to private citizen. 
They talk about 40% of sales, but that is bogus too. Read the story here.