Thanks for your response, which I mostly agree with. The only area of disagreement would be with gun-related misdemeanors. The problem here is where a gun-related felony gets plea bargained down to a misdemeanor. In this case, the perp should be put on the prohibited list.
The only suggestion that I can offer is related to policy more than legislation. More drug busts. Many young crooks like the ones who committed the mass murders tend to indulge in MDMA-related drugs (example, ecstasy for controlling young women), benzodiazepines (also used to rape), hallucinogens (other than MDMA), and of course marijuana.
Busts should yield weapons fairly often and get them prohibited for reasonable durations. That may not keep all them locked up for long for first offences, but the records should make it much easier to deal with them judicially afterwards.
It’s good for victims, too. Criminals without recorded histories can be much harder on victims (stalking, violent attacks and the like). They can be very slippery and tend to accuse victims.