In 2011, a shooting in Tucson, Arizona, was stopped when the gunman stopped firing in order to change magazines. The "high-capacity" magazine on his Glock pistol allowed him to fire 31 rounds before pausing. The Glock company website said that a standard magazine for its 9 mm semiautomatic pistol was between 13 and 17 rounds.[4]
In the 2012 Aurora shooting, a 100-round drum magazine used by the shooter jammed. According to one senior FBI agent, "If his firing mechanism had not seized, he could have wiped out the entire audience in a few minutes."[5] Although they delivering a large number of rounds, drum magazines are known to be unreliable, and heavy enough to significantly reduce accuracy. [6]
The debate regarding magazine capacity intensified in the U.S. after the 2012 Sandy Hook Elementary School shooting where an AR-15 style rifle with 30-round magazines were used by the shooter. In January 2013, President Barack Obama included a ban on gun magazines with capacities of more than 10 rounds in a list of gun-control laws he asked Congress to act on, but no legislation was successfully passed.[7]
The gunman in the 2013 Los Angeles International Airport shooting used a 30-round magazine for his Smith & Wesson M&P-15 rifle.[8] That was one of 17 high-profile mass shootings which involved the use of "high-capacity" magazines that were cited by the Los Angeles City Council when it passes a ban on possession of such magazines in 2015.[9] Other local incidents cited by supporters of the ban include the Los Angeles Jewish Community Center shooting and the 2013 Santa Monica College shooting.[10] Syed Rizwan Farook and Tashfeen Malik used 30-round magazines illegal in California during the 2015 San Bernardino attack. Four such magazines were in their possession.[11] Following the attack, there were calls for banning possession of "high-capacity" magazines in California.[12][13]