Background

Assault weapons and high-capacity magazines are exceptionally deadly. High-capacity magazines, commonly defined as ammunition magazines capable of holding more than 10 rounds, allow a shooter to fire more rounds without pausing to reload. The more rounds a shooter can fire consecutively, the more gunshot wounds they can inflict during an attack.

Assault weapons are generally high-powered semiautomatic firearms where each round has up to four times the muzzle velocity of a handgun round. This means that each round from an assault weapon inflicts greater damage to the human body than a round from a typical handgun. What’s more, assault weapons are generally designed to fire rounds at a greater rate than other firearms, and when combined with high-capacity magazines, they enable a shooter to fire more rounds over a short period.

Seven states and Washington, D.C. have some type of assault weapons prohibition in place. Nine states and Washington, D.C. have some type of high-capacity magazine prohibition in place. California ✔ ✔ Colorado ✔ Connecticut ✔ ✔ Hawaii ✔ ✔ Maryland ✔ ✔ Massachusetts ✔ ✔ New Jersey ✔ ✔ New York ✔ ✔ Vermont ✔ Washington, D.C. ✔ ✔

Key Findings

Assault weapons and high-capacity magazines are frequently used in mass shootings, resulting in more deaths and injuries. Over the past decade, the five deadliest mass shooting incidents in America all involved the use of assault weapons and high-capacity magazines (Las Vegas, NV; Orlando, FL; Newtown, CT; Sutherland Springs, TX; Parkland, FL). The 2009 Fort Hood, TX, shooter – who shot and killed 13 people and injured 32 more – specifically sought out high-capacity magazines in preparation for his attack. A witness to the shooter’s purchase at a Killeen, TX, gun dealer reported, “He gave me two specifications. He said he wanted the most technologically advanced weapon on the market and the one with the highest magazine capacity.”

A study of mass shooting incidents between 1981 and 2017 found that assault rifles accounted for 86 percent of the 501 fatalities reported in 44 mass shooting incidents. Study defines a mass shooting as an incident in which four or more people, not including the shooter, are killed with a firearm.An Everytown original analysis of mass shootings from 2009 to 2017 revealed that, of the incidents with known magazine capacity data, 58 percent involved firearms with high-capacity magazines. These shootings resulted in twice as many fatalities and 14 times as many injuries per incident on average compared to those that did not include the use of high-capacity magazines.

Assault weapons and high-capacity magazines are frequently used in the crimes that plague our nation. A recent study estimated that firearms equipped with high-capacity magazines, which include assault weapons as well as other high-capacity semiautomatic firearms, account for 22 to 36 percent of crime guns in most places, with some estimates upwards of 40 percent for cases involving serious violence, including homicides of law enforcement officers. The problem may be getting worse: research suggests the prevalence of high-capacity magazines in guns used in crimes has grown substantially since the 2004 expiration of the federal prohibition on assault weapons and high-capacity magazines.

Evidence

A growing body of research shows that states can reduce gun violence by prohibiting assault weapons and high-capacity magazines. States with restrictions on magazine size experience mass shootings at less than half the rate of states without restrictions. According to Dr. Michael Siegel, a researcher at Boston University, “Whether a state has a large capacity ammunition magazine ban is the single best predictor of the mass shooting rates in that state.”

A 2018 study found that mass shooting fatalities were 70 percent less likely to occur from 1994 to 2004, when the federal prohibition on assault weapons and high-capacity magazines was in effect, than during the 12 years studied before and after the prohibition. Researchers estimate a federal Assault Weapon Ban (AWB) would have prevented 314 of 448 mass shooting deaths that occurred during the studied periods where the AWB was not in effect.

In Virginia, the AWB was associated with significant reductions in the share of guns used in crimes that were equipped with high-capacity magazine, down to an all-time low of 10 percent in 2004. When the prohibition expired, the share of Virginia crime guns equipped with high-capacity magazines rapidly increased, reaching 22 percent by 2010.