In order to pass the 1994 federal ban, proponents had to accept two legislative amendments. First, the ban would sunset after 10 years. Second, the Department of Justice would commission a study of the ban’s effectiveness. The study would then provide members of Congress with information to help them decide whether to renew the ban or let it expire.
Attorney General Janet Reno’s staff selected the researchers, who produced their final report in 2004, which was published by the Department of Justice’s research arm, the [highlight=yellow]National Institute of Justice. It concludes: “we cannot clearly credit the ban with any of the nation’s recent drop in gun violence… . Should it be renewed, the ban’s effects on gun violence are likely to be small at best and perhaps too small for reliable measurement.”74 As the report noted, assault weapons “were used in only a small fraction of gun crimes prior to the ban: about 2% according to most studies and no more than 8%.”75 Most of the firearms that were used in crime were handguns, not rifles. Recall that “assault weapons” are an arbitrarily defined set of guns. Thus, criminals, to the degree that the ban affected them at all, could easily substitute other guns for so-called assault weapons.[/highlight]
https://www.cato.org/publications/policy-analysis/costs-consequences-gun-control