A 30-round magazine, left, and a 10-round magazine rest below an AR-15 rifle at the Ammunition Storage Component company in New Britain, Conn. (Charles Krupa/AP)

A ban on assault weapons — similar to the one enacted by Congress in 1994 — could be effective at reducing the number of people killed and injured in mass shooting attacks similar to the one in Orlando. But not necessarily for the reasons you might think.

A little background: Lawmakers routinely introduce assault weapon bans in response to mass shootings. Given that most recent public mass shooting incidents have involved the use of these weapons, this makes a certain amount of sense.

But some experts think that the amount of carnage involved in these attacks is less a function of the type of gun — assault-style rifle vs. handgun vs. what-have-you — but rather of the amount of ammunition that these guns can accommodate in their magazines. Your typical civilian assault rifle holds 30 rounds of ammo and can be reloaded in a few seconds.

Here's what you need to know about the guns some are calling "the gold standard for mass murder," after Orlando shooter Omar Mateen used the assault-style rifle Sig Sauer MCX to kill at least 49 people. (Editor's note: This video has been updated with more specific information.) (Gillian Brockell/The Washington Post)

One particular case illustrates this point: The shooter who killed six people and wounded 13 others, including U.S. Rep. Gabby Giffords, in Tucson in 2011 wasn't using an assault rifle. Rather, he had a standard Glock 9 mm handgun with an extended clip that held 30 roundsdouble the standard capacity for that gun.

The shooter was tackled by bystanders as soon as he stopped to reload. Had he only had a standard clip containing 15 rounds or fewer, it's possible that he could have been stopped sooner.

For that reason, legislation limiting the number of rounds that guns can carry to 10 or fewer could be one way to make it more difficult for shooters to injure lots of people.

The NRA points out that magazines holding more than 10 rounds are "standard equipment for semi-automatic handguns commonly owned and carried for self-defense," and says that the widespread adoption of assault rifles and high-capacity magazines coincided with a drop in crime. Researchers generally agree that many factors influenced the drop in crime in the '90s, and gun ownership was not one of them.

Here's where it gets interesting, though: A 2013 Washington Post investigation found that the 10-year federal ban on assault rifles drastically reduced the prevalence of high-capacity firearms in at least one state. In the latter years of the ban, the percent of weapons seized by Virginia police that were high-capacity (capable of holding 11 rounds or more) fell from 16 percent to 9 percent. In the years after the ban expired, the percent of high-capacity seizures rose rapidly to 20 percent by 2010.


Note: 1993 and 2010 are partial years only. The database was last updated in August 2010 and there were lags in reporting. Source: Washington Post analysis of Criminal Firearms Clearinghouse, Virginia State Police | | By Todd Lindeman/The Washington Post

Garen Wintemute, head of the Violence Prevention Research Program at the University of California at Davis School of Medicine, told The Post at the time that these numbers provide "about as clear an example as we could ask for of evidence that the ban was working."

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