Until the private sales of weapons are regulated, there will never be any meaningful legislation. You can create laws to require 1 year waiting periods, DNA collection, psych evaluations, polygraph tests, fingerprinting, background check, credit history, astrology, numerology, biorhythms and fung shui analysis of the person's place of residence. But it is all pointless if that person is legally allowed to take his purchase and then sell it to another individual without requiring any sort checks.

A law requiring all firearms transactions to happen at gun stores, gun shows and/or police stations, coupled with effective record keeping, or perhaps as simple as video recordings of the transactions would go a long way towards making sure firearms are only in the hands of "good guys".
Of course this will create burdens upon those locations, and additional hassles for persons selling or buying weapons.