What??? You couldn't be more wrong.
Conclusions
We identified five qualifying studies that estimated the effects of state assault weapon bans on different aspects of mass shootings. Gius (2015c) found that these bans significantly reduce mass shooting deaths but have uncertain effects on injuries resulting from mass shootings. Using similar models, however, Gius (2018) found that assault weapon bans resulted in significantly fewer casualties (deaths and nonfatal injuries) from school shootings.
FactCheck.org, Feb. 1, 2013: The final report concluded the ban’s success in reducing crimes committed with banned guns was “mixed.” Gun crimes involving assault weapons declined. However, that decline was “offset throughout at least the late 1990s by steady or rising use of other guns equipped with [large-capacity magazines].”
Ultimately, the research concluded that it was “premature to make definitive assessments of the ban’s impact on gun crime,” largely because the law’s grandfathering of millions of pre-ban assault weapons and large-capacity magazines “ensured that the effects of the law would occur only gradually” and were “still unfolding” when the ban expired in 2004.
A federal assault weapon ban was highly effective in reducing public mass shootings, reports a new Northwestern Medicine study just published in a pre-print.
news.northwestern.edu
Assault weapon ban significantly reduces mass shooting
A continuation of the federal ban could have prevented 30 public mass shootings