I believe that the majority of gun owners are responsible individuals. But with so many gun related deaths and injuries each year. Many caused not by harmful intent but by ignorance of gun safety. That it is reasonable to require people who own and use firearms to pass a standardized government test to prove that they know how to use and care for their guns.
I would recommend that in much the same way that a drivers license has different classes for various classes of vehicle, that the ATF would arrange for different levels of testing be required for the various classes for firearms (black powder; rifles; handguns; shotguns; est.).