The United States doesn’t require gun registration.

So, when U.S. Sen. Bernie Sanders, I-Vt., claims private citizens have more assault weapons than members of the military do, how does he know?

"There are more assault rifles, as I understand it, in the hands of private citizens than in the hands of the United States military," the 2020 presidential candidate said in the wake of the back-to-back mass shootings in El Paso, Texas, and Dayton, Ohio. "We're talking about 5 (million) to 10 million assault weapons in the hands of private citizens."

Sanders’ claim suffers a bit from comparing private and military weapons, which are different. Plus, he has to rely on wildly varying estimates, although his seems on the lower end.

We’ll sort out the facts for you.

Assault-style guns in both attacks

In both shootings, assault-style weapons, legal in both states, were used. Each weapon was semiautomatic — the gunmen could fire as quickly as they could pull the trigger — and carrying enough ammunition to potentially kill dozens of people in minutes.

The New York Times reported that the El Paso shooter used a semi-automatic Kalashnikov-style rifle (also known as an AK-47-style rifle), which typically uses a magazine that has 30 rounds; and that the Dayton shooter used an AR-15-style pistol, modified to act as a rifle, with a drum magazine that can hold up to 100 rounds.

Terminology problem

We’ll note that "assault weapon" does not have a universal definition. For example, a bill called the Assault Weapons Ban of 2018 defined an assault weapon differently than the federal law that banned assault weapons from 1994 to 2004, before expiring.

"None of the so-called ‘assault rifles’ legally owned by U.S. civilians are assault rifles as the term is used in military contexts," said Florida State University criminal justice professor emeritus Gary Kleck, who has done research on large-capacity firearms used by mass shooters.

"Assault rifles used by members of the military can all fire full automatic, like machine guns, as well as one shot at a time, whereas none of the so-called ‘assault rifles’ legally owned by U.S. civilians can fire full automatic."

But Kleck agreed that semiautomatic weapons evolved from earlier military weapons, many look like military weapons, and they can kill people rapidly.

The number of private weapons

Sanders campaign policy director Josh Orton acknowledged to us that the precise number of a particular type of weapon in civilian hands is not known, given there is no national gun registration. In fact, federal law prohibits there being a national registry.

But Orton argued that Sanders’ figure of 5-10 million of semiautomatic rifles, such as the AR-15, is a conservative estimate.

He cited a 2016 CNBC news article that quoted the National Rifle Association as saying there were 5 million AR-15s in circulation; he also cited other data suggesting the figure could be much higher.

Harvard University gun researcher Deborah Azrael told us that her latest survey of gun owners showed there were about 90 million rifles in private hands in the United States in 2015. The survey did not ask about about AR-15s, but 5-10 million is plausible, said she and her colleague on the survey, Matthew Miller of Northeastern University.

As recently as June 2019, the NRA called a reported figure of more than 11 million AR-15s "an arguably lowball figure."

Gun researchers including Kleck, Miller and Philip Cook of Duke University, cautioned us on relying on estimates made by the NRA or the National Shooting Sports Foundation, the firearms industry’s trade association. Those figures could be inflated with the aim of making assault-style weapons appear common.

"The fact is, we just don’t know" the actual number, Miller said.

Aaron Karp, a senior consultant to the Small Arms Survey and a political science lecturer at Old Dominion University in Virginia, told us he believes Sanders’ estimate for private citizens is "very conservative."

Karp estimates there are 15 million to 20 million assault-style weapons in the hands of Americans.

The number of military weapons

Gun researchers we consulted told us they are not aware of any counts of assault-style weapons held by members of the military.

Sanders’ campaign pointed us to an estimate of 4.5 million from the Small Arms Survey, an independent research project based in Geneva, Switzerland. That is for all U.S. military-owned firearms, not assault-style weapons. But it would be exceeded by the estimated 5 million or more assault-style weapons in private hands.

Our ruling

Sanders said: "There are more assault rifles, as I understand it, in the hands of private citizens than in the hands of the United States military. We're talking about 5 (million) to 10 million assault weapons in the hands of private citizens."

There are no official counts of assault-style weapons, either in private hands or in the U.S. military.

But estimates that the civilian figure could be 5 million or more appear to be conservative and would exceed the estimated number of all weapons in the military. At the same time, those are semiautomatic weapons, not fully automatic like those used in the military.

We rate Sanders’ statement Half True.