Closing these loopholes has been vehemently opposed by the NRA, which is why someone with an "F" from the NRA, which Hillary has, is desirable (in contrast to Bernie Sanders' D-). She promised in Connecticut to search for ways of tightening our gun laws every minute of her Presidency. That's what we need.
Passing effective gun control laws will be more difficult than the Affordable Care Act, due to the Second Amendment. New laws will require not only Hillary as President, but a Democratic Senate and House of Representatives, which is what it took to pass Obamacare. But in order for the new health care law to stand, it needed to also pass Supreme Court muster. And the country got lucky. The Republican-appointed Chief Justice Roberts decided to join the progressives in support of the law.
A new, strong gun-control law will not need such luck if Hillary is President, owing to the vacancy now on the Supreme Court with Antonin Scalia's passing. If the Senate confirms Obama's appointment Merrick Garland, which seems highly unlikely, there will be a moderate progressive fifth justice on the Court. If not, and Hillary wins, and the Senate goes Democratic, we'll either get Garland or an even more progressive new nominee from Hillary.
The possibility of a reliably progressive Supreme Court and a sensible, no-nonsense approach to gun control is one of the main reasons why the election of Hillary Clinton is so important. Just as Obamacare got us on the road, at long last, to universal heath care, gun control laws under Hillary Clinton could finally put America on a path away from the deaths by guns that daily ravage our country.