how do we know an assault weapon ban won't work?

The question for me has never been whether banning assault weapons will "work" or somehow stop all these events which seem to have a form of mental illness at their core combined with other factors. Of course it won't but that's an immature & extreme argument some like to use.. I guess thinking it somehow bolsters their views. Most reasonable folks recognize tha kind of thinking to be as silly as saying since mental health care, no matter how well funded, affordable & accessible will not prevent mental illnesss, it's a waste of time & money. Or that because seat belts won't prevent all death/injuries in car wrecks, they should be abolished.

The question is in our society today, would banning assault weapons along with stricter regs & background checks lessen the number of innocent deaths/injuries & the answer is yes imo. By how much, who knows but even it was only a small number it would be worth it. On the other side, you also have this ridiculous argument in regards to the interpretation of the 2nd amendment & what seems to be a in terms of tyranny & taking away all weapons which will never happen in this country. I suppose if gun makers came up with a weapon that shot missile like projectiles that blew up & burned bldgs and they became popular & widespreadly used by criminals & the mentally disturbed in mass killings, they would be defending their legality & sales/use as well.