You do have to have a background check at a gun show if you buy from a dealer. It is only if you purchase in a "private" sale that you do not have a check. The 40% number being tossed around is from a study started before the background check law became effective until shortly afterward. If I recall correctly, it involved about 250 transactions. Currently, those who do not have an agenda believe that the correct number is about 5% of gun sales are done without a check.
I should not have to have a background check on my grandson to give him a gun on his birthday. I have known him all his life.
More stringent background checks would not have prevented Columbine (straw purchaser), Gabby Giffords in Tucson, Aurora Theater or Sandy Hook.