Guns in America: How Criminals Might Be Purchasing Weapons Easily, No Questions Asked National Geographic undercover investigation obtained powerful firearms online.

July 16, 2013 -- To explore how criminals might easily get a gun, without background checks, from sellers who don't ask too many questions, an undercover team from National Geographic found private sellers online who, at separate meet-ups, were willing to sell them an assault rifle and a sniper rifle with enough ammunition to "start your own war."

The United States is the most heavily armed nation in the world, but despite gun regulations, weapons continue to fall into criminal hands.

There are an estimated 270 million civilian firearms in the U.S., a number that outranks other countries by leaps and bounds, according to the Small Arms Survey, a Geneva-based independent research project that is the leading international source of public information on firearms.

For National Geographic's "Inside: Secret America" series, investigative journalist Mariana van Zeller went undercover in Arizona with Jesse Torrez, a former police officer and firearms expert turned private investigator. The "Armed & Undercover" episode airs on July 17 at 10 p.m. on the National Geographic Channel.

Having spent years in law enforcement, Torrez is well-versed in how criminals in this country can obtain weapons and acted as van Zeller's guide throughout her investigation.

Van Zeller and Torrez's first attempt was to purchase an AK-47, a weapon designed for war and used by combatants in conflicts across the globe. It's a favorite among the Mexican drug cartels. Van Zeller and her team decided to try to purchase one off the Internet.

"We should be able to get you involved in a weapons transaction within 30 minutes," Torrez said, sitting at his computer with van Zeller. "And that's travel time, too. Using the Internet, it's very easy to purchase a weapon here in Arizona."

Their online search inquiries for buying AK-47s quickly turned up an ad from a gun seller that said prospective buyers should "call and ask for Nick."

Torrez instructed van Zeller through the call, telling her to tell Nick she could offer him $750 in cash for the assault rifle. Nick agreed to meet her and Torrez right away at a nearby Taco Bell parking lot to do the sale.

Before leaving, Torrez changed into a bigger shirt that could better conceal his weapon.

"[These transactions] have become less safe," he said. "Some people have gotten ripped off while they are making the transaction, either for the weapon or for the money. Even for $650 or $700, people will kill you for that."

Outfitted with hidden cameras, van Zeller and Torrez drove to the parking lot of a Taco Bell to meet Nick.

"It's really scary waiting for someone to pull up who you know has an AK-47," van Zeller said.

When Nick arrived, he offered to have van Zeller and Torrez take a look at the weapon before they bought it. He also had "several" AR-15S for sale, if they were interested. After handling a few of the assault rifles, van Zeller and Torrez decided to go through with their original plan and purchase the AK-47.

In Arizona, private gun sales are legal and no background checks needed. About 40 percent of gun sales nationwide are done privately. Sellers should have a bill of sale signed and ask for identification, but Nick didn't even ask Torrez and van Zeller for IDs. He pocketed the cash and they all went their separate ways.

"We would have had three rifles in less than an hour, all of which are the military-style weapon," Torrez said.

He also noted the gun came with a few rounds of ammunition and was "all ready to go."

"This is a typical Russian round," Torrez said, holding a large clip. "It'll penetrate all body armor except for level-3 body armor and above … and he wouldn't have had a trace of who I was."

Torrez said these sorts of private transactions happen every day. In 2010, there were more than 5 million firearms manufactured in the U.S., according to the latest statistics from the Bureau of Alcohol, Tobacco, Firearms and Explosives.

Van Zeller and Torrez next set their sights on buying a .50 caliber sniper rifle, a weapon so powerful that the U.S. military uses it to penetrate concrete and steel.

Again, they took to the Internet to search for sellers and found one willing to sell them a .50 caliber within a matter of minutes. Van Zeller and Torrez again donned hidden cameras and drove to meet the seller at his house.

When they arrived, a man named Mike invited them into his garage to negotiate the purchase.

"This could literally penetrate steel," Mike told van Zeller, as he handled the sniper rifle. "In Iraq, they told the snipers, don't waste one round on one person, even if he is standing behind a brick wall. Usually they'll have two, three guys lined up, then they shoot because it would go through the brick wall and all three of them."

Mike then showed her the gun's ammunition, which he was selling for $15 per bullet.

"You're getting 11 boxes with 12 rounds apiece, so you have a lot of firepower to start your own war," he said.

After making the purchase, van Zeller and Torrez looked over the .50 caliber, one of two incredibly dangerous weapons they managed to purchase within a couple of hours.

"Definitely not a lot of people have these weapons," Torrez said. "It's a war gun. All you need is a finger to pull the trigger."