13 questions about guns in the United States and the surprising answers

— -- The ongoing national conversation about possible changes to gun laws has prompted questions about the way the system works currently.

The way in which federal laws mandate gun sales records be kept – though not shared – makes it difficult to have an accurate account of the number of guns in the country.

Edgar Domenech, a former deputy director of the Bureau of Alcohol, Tobacco, Firearms and Explosives, answered some of the most common questions about the state of firearms in the United States.

How many gun owners are there in the United States?

That’s not known.

“There is no national registration, there is no law or registry on the books that requires that gun owners have to either registered or convey how many guns they actually own,” said Edgar Domenech, a former deputy director of the Bureau of Alcohol, Tobacco, Firearms and Explosives.

Domenech noted there is no federal law that requires gun owners to be registered, but there are some states and cities, like New York City, that require owners to register their weapons with local authorities.

According to a Pew Research Center study, released in June 2017, 30 percent of American adults own a gun and a further 11 percent said they live with someone who owns a gun, meaning that 41 percent of adults lived in a household with a gun.

The Pew study noted that among gun owners, 32 percent own one gun, 37 percent own two to four guns, and 29 percent own five or more guns.

How many guns are there in the United States?

Similarly, because of the lack of national cohesion on various records, no one knows exactly how many guns are in the country.

“ATF does not maintain a federal gun registry, therefore, records are not kept on the sales of firearms, private sales or information on individual purchasers,” an ATF spokesperson told ABC News.

Domenech said it’s “safe to say there are hundreds of millions of firearms” in the country.

One way to measure the number of guns in the country is the annual commerce report released by the ATF, which reports how many guns were manufactured in the United States in a given year. The only readily available data from ATF commerce reports date from 1986 through 2015, the most recently released report, and there were 143,642,781 guns manufactured in the U.S. during that time.

Because firearms are not biodegradable, it is very easy for a gun to last for decades so long as it is cleaned and stored properly, meaning that guns that were manufactured much earlier in the 20th century may still be in circulation.

By contrast, it’s also unknown how many guns drop out of circulation, either by being destroyed or seized by law enforcement.

One estimate said that there were believed to have been 310,000,000 guns in the U.S. in 2009, according to a Congressional Research Service report published in November 2012, though gun sales are believed to have increased in the years that followed.

What is an FFL?

An Federal Firearms License (FFL) is the document that allows an individual or company to buy, sell, or manufacture firearms in the U.S. FFLs are issued and monitored by the ATF, and they are the ones who the ATF reaches out to if a question is raised about a gun that is involved with a crime, for example.

What happens when someone buys a gun through an FFL?

They have to fill out an ATF-issued 4473 form, which includes standard identifiable information like the applicant’s address, age, sex, date of birth, and ethnicity. It also asks if they have ever been convicted of a felony, are an unlawful drug user, have ever been committed to a mental institution, been dishonorably discharged from the armed forces, convicted of domestic violence, and are a legal resident of the U.S.

That form is kept on paper, and then the FFL needs to electronically forward information from that form to the National Instant Criminal Background Check System (NICS), which is overseen by the FBI. The purpose of that NICS review is to see if there’s any prohibitive factor that should prevent someone from being allowed to buy a gun.

NICS is given up to three days to answer, either saying that the applicant is approved or denied the sale. If NICS doesn’t respond in three days, the sale is approved by default. If the person is denied, the FFL will just know that their application is denied but will not know the specifics of what prompted the denial, Domenech said.

What are other ways that people can buy guns?

Beyond buying guns from stores, many of which are FFLs, people can also buy guns through private sales, which means that they are buying directly from the owner of the gun. In that situation, the seller is said to be selling the firearm from their personal collection which could have been passed down through generations or bought directly by the seller from manufacturers or other FFLs.

What happens when people buy guns through private sales?

There are no federal requirements that private sellers need to meet when they sell firearms, meaning that they don’t have to run a background check, ask for identification, or have their customers fill out any forms.

What happens when someone buys a gun at a gun show?

Gun shows involve sales by FFLs, who set up tables at gun shows, or by private sellers, who are also allowed to sell at gun shows. If the seller is an FFL, then they have to go through the same process as they would at a store, having the applicant submit a 4473 and waiting up to three days before giving the either approval or denial. If it is a private seller, there is no background check required.

Is it possible to look up the age or medical history of someone who bought a gun?

The only record that states the gun owner’s age or medical history is the 4473 form, which the FFL is required to keep but is not passed along to any other authority unless upon specific request.

As for medical history, the applicant doesn’t need to submit any medical records or doctors notes with their applications, meaning that it is just up to them to self-identify any issues.

Why are people allowed to buy some guns at 18 years old and why do you have to wait until you’re 21 years old for others?

Because the law says so. The Gun Control Act of 1968 stipulates that no rifle or shotgun or matching ammunition can be sold to someone younger than 18 years old, and no handgun or ammunition could be sold to anyone younger than 21 years old.

“Long guns and shotguns were deemed more of sporting type of firearm than a pistol or revolver when the law was enacted in 1968, in my opinion,” Domenech said based on his years at the ATF.

How are gun records stored?

All ATF records about gun sales or owners are kept on paper, not electronically, making it difficult to search the records. And the reason isn’t the they just haven’t entered the 21st century: the ATF is legally prohibited from doing so.

A line has been added to ATF appropriations bills that says that no funds “shall be available for salaries or administrative expenses in connection with consolidating or centralizing, within the Department of Justice, the records, or any portion thereof, of acquisition and disposition of firearms maintained by Federal firearms licensees,” as it says in the 2012 appropriations bill.

“It was always understood that this was the position of the NRA that they didn’t want to have any government entity to have what was construed as a national registration record keeping system,” Domenech said.

“I think their thinking was is that it could in fact infringe on an individuals' personal right regarding the Second Amendment issue and they just felt that the government didn’t need the ability to know who has a firearm and who doesn’t,” he said.

The NRA did not respond to ABC News’ request for comment.

When a gun shop closes down, they are required to pass their records over to the ATF’s Out of Business Records Center.

Domenech says that as of 2010, when he left the ATF and became the sheriff of New York City, the records that were sent to the Out of Business Records Center were then put on microfiche, rather than in an electronic database.

“You can see the complexity of when you have a paper records keeping system that is designed,” Domench said, noting there are “a lot of potential pitfalls.”

How are traces run on guns involved in crimes then?

When law enforcement is looking for information on the owner of a gun that is connected to a crime, they run an electronic trace, or e-trace, on the gun.

By looking up the gun’s serial number the ATF can determine the manufacturer of the gun, and the manufacturer can tell the ATF which FFL got that weapon. Then the FFL uses their Acquisition and Disposition (AAD) book to look up the 4473 form that the purchaser of that gun had to fill out when they bought it in the first place.

“The tracing process is a paper process. And like anything else when it’s a paper process it’s not as efficient if it were in fact redesigned to meet what we have in today's electronic age,” Domenech said.

What is the National Instant Background Check System (NICS)?

NICS is the system, which is run by the FBI, that determines whether someone can legally buy a gun.

NICS was mandated as a result of the Brady Handgun Violence Prevention Act of 1993, which was named in honor of James Brady, the assistant to President Ronald Reagan who was shot in the 1981 assassination attempt. It was put into effect in 1998.

A NICS check goes through records from the National Crime Information Center, the Interstate Identification Index and the NICS Index. The information that individual states provide to the NCIC database differs by state.

On the FBI’s undated website explaining NICS, it states that more than 230 million checks have been run and it has resulted in more than 1.3 million denials, which equals 0.56 percent of checks lead to a denial.

What happens if you lose your gun?

Giffords, a gun violence prevention advocacy group associated with former Rep. Gabby Giffords, reports that nine states – California, Connecticut, Delaware, Illinois, Massachusetts, New Jersey, New York, Ohio and Rhode Island -- and the District of Columbia require owners to report the loss or theft of a firearm to law enforcement. Maryland requires the reporting of loss or theft of handguns and assault weapons but not other guns, and Michigan requires the reporting of thefts but not the loss of firearms.

Domenech notes that responsible gun owners tend to report a loss or theft to their local police department because then, if the gun is later used in some kind of crime, the individual will be able to have a record of reporting the weapon lost or stolen.