Can an assault weapons ban reduce killings if firearms last 100 years?

Six days before a man shot and killed 10 people, he legally purchased the military-style firearm he used for the crime. The incident – one of three recent mass shootings – yet again renewed a public debate about banning assault weapons in the US and seems like a potential example of a shooting in which an assault weapon ban might have been effective in reducing the death toll of the attack. But would it?

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When firearms are recovered by law enforcement because of their use or suspected use in a crime, the weapons are recorded in a database along with the date of their first retail sale. The amount of time between those two events is known as the “time to crime” and is published by the US Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF). While the suspect involved in the Boulder shooting waited just six days, the national average time to crime is 8.3 years, according to 2019 statistics from the ATF.

This dataset is much broader, since it includes a wide variety of crimes and suspected crimes, but the number still poses a significant problem for policymakers that are attempting to prevent future mass shootings. Even if a nationwide ban on sales were effectively implemented tomorrow, there would still be somewhere between 15m and 20m assault rifles in circulation out of the estimated 393m guns held in the US.

Averages can be misleading, though: the range here is pretty vast – guns can be recovered days or decades after purchase. But it is relevant to note that in only 7% of cases were the guns recovered less than three months since the purchase date. State differences are also huge. In Arizona, 12% of recovered firearms were purchased less than three months ago, while in Connecticut and Arkansas, it’s just 4%.

The fact that those weapons could continue to be used for years to come isn’t just a hypothetical given the lifespan of assault weapons. Firearms remain operational for a century or more, further complicating any path to reform in a country with the highest gun ownership rate per capita in the world.