No private sales?

Yeah, there's no possibility of them halting all private sales.

Not going to happen, especially between close friends and family members. If they ever make this into a law where it was actually illegal and their efforts to prosecute private gun sales could possibly result in a conviction many would just go around this law by back-dating a receipt, only selling a gun of theirs to someone they trust and lawyering up in the event the police come to their door. Unless they sold a gun to a criminal who came into contact with the police as the result of a crime and they actually followed up on who owned it originally I don't see how that's going to happen.

Other than at work I haven't come into contact with any cops for years and years, most people are similar as they aren't out there running amok or doing anything that attracts the attention of the police. So I think they're way overestimating their capability in both being able to track guns and their ability to prosecute normally law-abiding citizens (other than Malum prohibitum laws like this one has the potential to be). Middle class citizens have way more resources at their disposal than a crack addled felon does. So their chances of coming into contact with the police are less to begin with.