According to the Supreme Court, arms that are in common use for lawful purposes are, prima facie, protected by the Second Amendment. Unless an arm is both "dangerous and unusual", its purchase, possession, and carrying are covered under the right to keep and bear arms. 

When it comes to "large capacity" magazines, a new study from the National Shooting Sports Foundation reveals that they are absolutely in common use. In fact, magazines that can accept more than ten rounds of ammunition are the national standard, according to the NSSF. 

The Detachable Magazine Report (1990-2021) confirms what NSSF has known – that the national standard for magazine capacity for America’s gun owners is greater than 10 rounds. With nearly 1 billion detachable magazines in circulation, for both rifles and pistols, they are unquestionably commonly-owned and commonly-used for lawful firearm use, including recreational target shooting, hunting and self-defense. They are “arms” within the meaning of the Second Amendment. Detachable magazines are integral to the design of, and necessary for the proper functioning of, today’s modern semi-automatic firearms.

“The data establishes that law-abiding gun owners overwhelming choose magazines that have a capacity to hold more than ten rounds for lawful purposes including self-defense, target shooting and hunting,” said Lawrence G. Keane, NSSF Senior Vice President & General Counsel.

About 46 percent of the magazines estimated in this study are rifle magazines with 30+ round capacity. The percentage of detachable magazines at 11+ capacity is about 55 percent of total pistol magazines. The amount of 10 and below capacity rifle magazines supplied from the manufacturer is over one and a half times the amount of 30+ capacity rifle magazines. The consumer market totals of rifle magazines show 30+ capacity magazines, over 413 million, are over 30 times the amount available than 10 and below capacity rifle magazines, about 13 million.

Further examination of the data proves that of the 717,900,000 detachable magazines for pistols and rifles with a capacity greater than 10 rounds, 209,145,000 pistol magazines are in circulation from combined sales through firearm manufacturers (those magazines included with the firearm) and aftermarket production. Rifle magazines with a capacity greater than 10 rounds accounted for 508,755,000 and rifle magazines with a capacity of 30 rounds or greater totaled an estimated 448,369,000 from combined sale of those included with a firearm at sale and the aftermarket.

Just 245,872,000 pistol and rifle magazines with a capacity of 10 rounds or less are in circulation when accounting for the magazines included with a firearm from the manufacturer and the aftermarket.

According to the NSSF report, "large capacity" magazines make up almost 80 percent of the nearly 1 billion magazines in circulation, and when given the choice consumers overwhelmingly purchase magazines that can accept more than ten rounds. NSSF estimates that about 13.7 million rifle magazines that can hold ten rounds or less were purchased on the consumer market between 1990 and 2021, while almost 414 million rifle magazines with a capacity of at least thirty rounds were sold during the same time period. 

The figures are closer when it comes to pistol magazines, but "large capacity" purchases (112,997,000) still outnumbered "standard capacity" magazines (110,694,000) over the past three decades. 

These new figures won't stop anti-gun activists (and even some judges) from declaring that magazines aren't "arms" to begin with and therefore have no Second Amendment protections. We're still going to hear politicians like California Attorney General Rob Bonta proclaim that these magazines aren't commonly used for self-defense, and that the "average" defensive gun use involves fewer than three rounds being fired. But the data that the NSSF has compiled is proof positive that the vast majority of magazines in the United States can hold more than ten rounds, they are in common use, and are owned by an overwhelming number of lawful gun owners. They're not unusual. They're the norm, and that means they're covered by the text, history, and tradition of the Second Amendment.