So you're against keeping a data base of folks with felony convictions that gun stores must check before selling a firearm? According to Hoodat, that law prevents 48,000 legal sales per year.
GIGO. It didn't work because it wasn't followed by the agencies which should have reported the problem in the first place, so the firearm could not have been
legally purchased. A relatively minor impediment, but one that may have heralded a problem that was developing. That would not have stopped the determined criminal form getting one, but it would have stopped him from purchasing the rifle legally.
However, that law didn't work. Because his priors had not been reported by the Air Force, and likely another law (HIPAA) prevented the release of the mental Health information that also could have been enough to prevent that sale or flag the attempt.
We don't need any more stinking laws. We need for the people who are charged with enforcing those laws to do so, with the laws we have.
In the mean time, If I want to buy, sell, or trade my legally owned firearms with another person, someone who is not a criminal or mentally deficient, I am free to do so. If something seems sketchy about that, i am always free to nix the deal, and would feel morally obligated to not conduct a private deal.
Concentrating on the tool ignores the hand that wields it, and imho, that is the problem here, not the same type of rifle that ended the rampage, but the type of person behind it.