You're doing it wrong.  All this effort to control inanimate objects is misguided and absurd.  

Guns do not cause mass shootings, insanity does.  Statistically, nearly all mass shooters are mentally ill.  To nearly eliminate mass shootings we must identify, treat, and adjudicate the mentally ill so they cannot possess firearms.

Guns do not cause crime, socioeconomic factors do.  Statistically, most violent crime is perpetrated by repeat offenders.  Prosecute and lock up criminals, and violent crime will decrease.

Problem solved without punishing the law-abiding by trampling on a God-given and constitutionally-enshrined right.