I had to pass a background check where they interviewed some of my high school friends and I am sure they checked every criminal data base the NSA can access. I don't know who else they interviewed but only my friends told me they were questioned but just because I am sure I can pass whatever does not mean I think they should do that to you just so you can buy a gun. Pretty much everyone who get the kind of screening I went through passes because if you are not going to pass you don't want them looking so you don't apply for jobs that require the clearance. Your employer has to pay for the screening, and it is tens of thousands of dollars.
Tim