When is a gun really a gun?

That’s the question police had to answer recently when investigating a Vernon Hills man who acquired gun parts and built his own firearms.

The man’s home was searched April 12 as part of a college threat assessment after a tip about his interest in guns and a sighting of him at College of Lake County wearing clothing tied to a white nationalist group.

Jakub Zak, 19, pleaded guilty Aug. 6 to a reduced gun possession charge after police said the teen was in possession of home-built firearms known as ghost guns. In total, he was in possession of five guns in various stages of completion including some that could be fired, police said.

In a negotiated plea deal, Zak was sentenced to 18 months of probation. Under the terms of the agreement, Zak cannot possess weapons, weapon parts or ammunition. He is also barred from the use of drugs or alcohol and has to complete 100 public service hours.

The condition specifically prohibiting Zak from possessing firearm parts — which is similar to a condition of his bail that required him to relinquish various tools — was included because he built the guns that were seized from his home, according to Vernon Hills Police Chief Patrick Kreis.

Zak did not respond to requests for comment.

The case highlights how the line between a gun part and an actual gun can come down to a few holes.

A receiver — or the frame of a gun to which most of the parts eventually connect — is legally considered a gun, according to Kreis.

Federal law allows purchasers to legally buy or transfer parts that are no more than “80 percent” of a gun, according to Kreis. He said a block of metal shaped like a receiver but not fully drilled to accommodate screws or a barrel is considered less than 80 percent of a gun, and can therefore be sold outside of the laws that regulate a completed firearm purchase.

“State law requires you to have a FOID card to possess any firearm,” Kreis said. “That’s what he was charged with, but he wasn’t in violation of any federal law for buying a gun without a dealer or for completing the gun.”

Eighty percent lower receivers and gun-building kits can be purchased online with relative ease, Kreis said.

Although he’s not familiar with the easiest method, Kreis said the drilling process can definitely be done without an industrial-grade drill press.

“Some of the vendors selling the 80 percent kits also provide the instructions for how to ‘do it yourself,’” Kreis said. “It would be a mistake for someone to think you need a $30,000 piece of industrial machinery to complete these weapons.”

Court documents show officers seized three ArmaLite rifles — commonly known as AR-15s — a .40 caliber semi-automatic pistol and a 9mm semi-automatic pistol from Zak’s home in the 300 block of Ashwood Court.

Kreis said some of the items collected were receivers still in progress while others were fully functional guns that police tested at a crime lab.

“When these things are built, they’re built without any serial number,” Kreis said. “They never, ever make a record of them. So when one of (the guns) shows up at a crime scene, we have no idea where the lawful provenance of that firearm comes from.”

Federal law only requires serial numbers on guns that are transferred between individuals or those that are built for commercial reasons, according to the Bureau of Alcohol, Tobacco, Firearms and Explosives.

Kreis said growing up he knew people who would make primitive musket-style muzzle-loading rifles.

“When I look back on it, it’s an extension of this longstanding process of allowing firearm enthusiasts or craftsman or woodworkers to finish those kind of guns,” Kreis said. “An AR-15 is a whole different deal. A Glock pistol is a whole different deal.”

Kreis believes gun-building kits should have serial numbers and be sold at licensed stores as a modern compromise.

“People are able to make high-performance firearms that I believe should only be sold through legitimate firearm dealers or legitimate private sales that meet all the requirements,” Kreis said.

Kreis said some people ineligible for a FOID card “skirt” the system by building guns through the legal purchase of an 80 percent receiver and the additional parts to complete the firearm.

In some cases, Kreis said ghost guns have been stolen from building enthusiasts.

Zak’s home was searched by police April 12 following an anonymous tip about the teen’s interest in guns and a sighting of him at College of Lake County wearing clothing that promoted a group known as Patriot Front, according to Kim Christenson, spokesman for the Vernon Hills police department.

“Patriot Front is a white supremacist group whose members maintain that their ancestors conquered America and bequeathed it solely to them,” according to a post on the Anti-Defamation League’s website.

The group promotes racism, anti-Semitism and intolerance under the guise of preserving ethnic and cultural origins of their European ancestors, according to the Anti-Defamation League.

“We didn’t charge him with anything to do with that,” Kreis said. “Our investigation didn’t find any reason to go down that path.”

Although ammunition and functional weapons were found in Zak’s home, Kreis said investigators found no evidence of any intent to use them in any illegal activities.

“There wasn’t any indication that these firearms were going to be used in a criminal manner,” Kreis said, while reiterating that possession of guns and ammunition without a FOID card is unlawful.

Connie Shanahan, a store manager at Just Target Guns in Libertyville, said he’s unfamiliar with the 80 percent receivers because all of his colleagues and customers prefer to deal with “legitimate” and “field-tested” products.

“I guess there’s a market somewhere, but for us there’s no market here and no profit in it, and we wouldn’t want to upset the local police,” Shanahan said. “I think most legitimate gun shops feel the same way.”

Just Target Guns has customers who like building their own custom guns, but Shanahan said they always want a fully-built receiver with a serial number.

“I’ve had police officers, hobbyists, hunters want to do it, but they all go through legitimate process of buying it as a gun and getting a background check,” Shanahan said. “But even some of them have problems and end up asking us for help because it takes some skill to assemble a gun.”

Shanahan said regulated parts also come with a sense of reliability from prior testing, compared to the novice use of drills or mathematical designing that could lead to a harmful misfire.

How to dispose of a ghost gun is also of concern to consumers, Shanahan said. Without a serial number, Shanahan said the custom guns must be sawed into pieces that prevent it from ever being functional again.