From An Updated Assessment of the Federal Assault Weapons Ban - NCJRS (PDF):
https://www.ncjrs.gov/pdffiles1/nij/grants/204431.pdf
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9.4. Summary
Although the ban has been successful in reducing crimes with AWs, any benefits
from this reduction are likely to have been outweighed by steady or rising use of non-
banned semiautomatics with LCMs, which are used in crime much more frequently than
AWs. Therefore, we cannot clearly credit the ban with any of the nation’s recent drop in
gun violence. And, indeed, there has been no discernible reduction in the lethality and
injuriousness of gun violence, based on indicators like the percentage of gun crimes
resulting in death or the share of gunfire incidents resulting in injury, as we might have
expected had the ban reduced crimes with both AWs and LCMs.
However, the grandfathering provision of the AW-LCM ban guaranteed that the
effects of this law would occur only gradually over time. Those effects are still unfolding
and may not be fully felt for several years into the future, particularly if foreign, pre-ban
LCMs continue to be imported into the U.S. in large numbers. It is thus premature to
make definitive assessments of the ban’s impact on gun violence.
Having said this, the ban’s impact on gun violence is likely to be small at best,
and perhaps too small for reliable measurement. AWs were used in no more than 8% of
gun crimes even before the ban. Guns with LCMs are used in up to a quarter of gun
crimes, but it is not clear how often the outcomes of gun attacks depend on the ability to
fire more than 10 shots (the current limit on magazine capacity) without reloading.
Nonetheless, reducing crimes with AWs and especially LCMs could have non-
trivial effects on gunshot victimizations. As a general matter, hit rates tend to be low in
gunfire incidents, so having more shots to fire rapidly can increase the likelihood that
offenders hit their targets, and perhaps bystanders as well. While not entirely consistent,
the few available studies contrasting attacks with different types of guns and magazines
generally suggest that attacks with semiautomatics – including AWs and other
semiautomatics with LCMs – result in more shots fired, persons wounded, and wounds
per victim than do other gun attacks. Further, a study of handgun attacks in one city
found that about 3% of gunfire incidents involved more than 10 shots fired, and those
cases accounted for nearly 5% of gunshot victims. However, the evidence on these
matters is too limited (both in volume and quality) to make firm projections of the ban’s
impact, should it be reauthorized.
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