The latest shooter was being tracked/watched etc. How would any proposal above have prevented her from killing?
I went overly hyperbolic, posted some pics of extremists stating they wanted to kill "Christcucks" while holding AR patterned rifles, and said detain and interview/investigate them. It was met with an appropriate amount of personal liberty and un-Constitutional challenge.
My point in doing so - they had guns and are making unveiled threats at a certain group. And none were arrested unless they acted out. What, short of drastic measures, would've saved lives?
Using the mag limit example, do you think a sociopath, having access to a drum mag or 30 round mag, will give second thought to using one before a spree? Or do you intend the next 50 years to be safer through enforcement? Because in that scenario, only the law-abiding would consider compliance.