In the back room of Steven Bowman's Crossroads Firearms, there's a lot of paperwork. 

Filing cabinets hold thousands of copies of the form that buyers have to fill out to get a gun. 

"It asks things like are you the actual buyer of the firearm? Are you buying a firearm for somebody else that can't buy a firearm?" Bowman said, reading off the official Justice Department form. 

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It's designed to make sure people who aren't supposed to have guns don't get them.

But online private sales don't have those safeguards and despite Facebook policy against it, people are still selling guns on the site.

10News looked into this after a viewer sent us a screenshot where he said he tried to ask about buying a gun case -- and received a photo of the gun inside instead. 

Photo from viewer
This is the screenshot a viewer said he received after asking about a gun case for sale on Facebook Marketplace.

"They're selling a box for 500 dollars, but the contents in it is a gun and that's free," Bowman explained. 

When 10News looked Wednesday, we found more than a dozen gun cases for sale in our area for more than $400. 

Some might just be the case for sale -- and even if not, Jeff Lindsey with the UT Law Enforcement Innovation Center said there's no law against private gun sales.

"There's an expectation that the gun owner, the purchaser or the seller, be responsible in terms of doing their due diligence," he said. 

Still, some rules do apply. 

"You cannot transfer a firearm to someone that is intoxicated or using alcoholic beverages," Lindsey gave as an example.

But private sales, without the type of records Bowman keeps, can make it tough for law enforcement to investigate if the gun is used in a crime. 

"It's perfectly logical and routine to try to trace a history of a weapon," Lindsey said. "And there are some gaps."

He said both seller and buyer should use common sense and ask "whether or not this is an individual that should be buying a weapon or I should be buying a weapon from."