I've got an idea on how to make sure that only responsible people who are in their right mind get legally access to guns:
1. People with a criminal record in association with a violent crime or a sentence of more than a year can't get guns. (There is probably already something similar)
2. Anyone who wants to get a gun, has to have five adult bondsmen who would be charged and sentenced the same as that person, if that person commits a crime with a (any) gun during the next ten years.
That way only someone who is obviously trustworthy to other people (=small part of society) would legally get access to guns.
What do you thinkż