Christopher S. Koper

"Results suggest assault weapons (primarily assault-type rifles) account for 2–12% of guns used in crime in general (most estimates suggest less than 7%) and 13–16% of guns used in murders of police. Assault weapons and other high-capacity semiautomatics together generally account for 22 to 36% of crime guns, with some estimates upwards of 40% for cases involving serious violence including murders of police. Assault weapons and other high-capacity semiautomatics appear to be used in a higher share of firearm mass murders (up to 57% in total), though data on this issue are very limited. Trend analyses also indicate that high-capacity semiautomatics have grown from 33 to 112% as a share of crime guns since the expiration of the federal ban—a trend that has coincided with recent growth in shootings nationwide.... AW [assault weapon] laws also commonly include restrictions on large-capacity magazines (LCMs), which are typically defined as ammunition feeding devices holding more than ten rounds of ammunition (some laws have higher limits). LCM restrictions are arguably the most important components of AW laws in that they also apply to the larger class of high-capacity semiautomatic firearms without military-style features. In the broadest sense, AW-LCM laws are thus intended to reduce gunshot victimizations by limiting the stock of semiautomatic firearms with large ammunition capacities and other features conducive to criminal use.... Importantly, trend analyses suggest that LCM firearms have grown substantially as a share of crime guns since the expiration of the federal ban on AWs and LCMs."

"The most important feature of the previous ban was the prohibition on large-capacity ammunition magazines. A large magazine is arguably the most critical feature of an assault weapon, and restrictions on magazines have the potential to affect many more gun crimes than do those on military-style weapons. Restrictions focused on magazine capacity may also have a greater chance of gaining sufficient public and political support for passage than would new restrictions on assault weapons, though current polling suggests that both measures are supported by three-quarters of non-gun owners and nearly half of gun owners."