Let me explain how our government really works: Congress passes a b******t law, and then gives the appropriate agency the power to write the regulations needed to implement that law.
So, what happens, you have BATF deciding what is and is not a flash suppressor, etc. Then there are "rulings". This is where some poor schmuck is arrested for whatever, and the BATF sees if they can make their regulations stick in his case.
OK, what will happen if this law is passed, BATF will write the regulations, and the ONLY way they can regulate private sales is to establish universal gun registration. Yes, every single one of your guns will have to be registered, or it will be illegal. Then if you have a gun that is not on their list, off to jail you go. Or if they come to your house for their however often inspection, and you don't have that Ruger 10-22 that is clearly listed (that you sold to a guy down the street), then off to jail you go.
THIS is what will really happen with the "Gun Show Loophole" bill, if passed.