Police started their efforts to confiscate the guns during a traffic stop near Baseline and G Streets, just east of the 215 Freeway in San Bernardino.
They haven't shared exactly why they pulled this driver over, but when they did, they said 23-year-old Romeo Duro had narcotics and a loaded ghost gun.
"A ghost gun is an un-serialized firearm," said Sgt. Equino Thomas. "It's a gun that is basically put and pieced together."
Legally owned guns are registered and can be traced back to the owner.
The arrest opened the door for San Bernardino's Gangs and Narcotics division to get a warrant for a home five miles west in Rialto.
When police walked in, they told ABC7 they found the second suspect, identified as 24-year-old Kevin Scherling, surrounded by what is now considered evidence.
It includes three 3D printers, 12 handguns, one MAC-11 submachine gun, 17 magazines, fully automatic conversion kits and more than 1,000 rounds of ammunition.
Sgt. Equino says Scherling was in the process of making ghost guns when officers arrived at the house.
Both suspects are now facing felony drug and weapons charges.