CARSON, Calif. – Law enforcement calls them 'ghost guns,' but gun store owners call them '80 percenters' - meaning an unfinished fiream, that's about 80 percent of the way there.

And because it's not technically a gun, you can have one delivered straight to your home - without a trace.

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“They’re kind of like Legos," said gun shop owner, Jack Brandhorst. "They’re so simple.”

Brandhorst's by-appointment-only shop is located in Carson.

 As a licensed dealer, any weapon he works on has to be registered in the State of California. But anyone can buy an unfinished firearm on the internet and finish putting it together at their own home.

The practice is common.

“An eighty percenter won’t have these holes," said Brandhorst. "You have to drill them and you have to drill this part out.”

Eighty percenters are available online, no background check required. You can have it shipped directly to your house.

Some kits even come with the tools you need to finish assembling the firearm.

They don't have serial numbers and there's no required record of the sale.

There is, however, a 2016 law requiring Californians to register the weapons.

Brandhorst sees it as another misguided attempt to curb gun violence, by restricting legal gun owners. 

“It’s a well intentioned law but it’s not going to stop a maniac from perpetrating violence,” he said.

He showed us a number of modifications on AR-15s required by California law. Brandhorst says he and his customers all follow the rules, even the ones they don't agree with. 

“I think everyone should have to pass a background check,” Brandhorst said.

But he's not a fan of registration. 

“The only reason for the government to tie a serial number, make and model to your name is for confiscation,” he said. 

He says it's that concern that's made eighty percenters popular, even among legal gun owners.

Although it's impossible to know just how popular the weapons are, since they exist . . . without a trace.