A morbidly obese Melbourne man has been jailed for importing "truly terrifying" machine guns from the United States, but dozens of the firearms he smuggled remain on the streets.
Paul Munro, 64, was on Wednesday jailed for at least six years by Victoria's County Court for importing Thureon fully-automatic machine guns and semi-automatic handgun parts between 2012 and 2016.
Munro decided to illegally import the Thureon machine gun, which can fire up to 1000 rounds per minute, after he went to a gun show in Las Vegas.
The mechanic later asked Thureon Defense owner Andy Huebschmann, based in Wisconsin, to send him the machine guns hidden in the false base of containers holding engine parts.
Munro also asked Huebschmann to send him triggers that would convert other semi-automatic guns into fully automatic weapons.
"The Thureon in fully automatic mode is a truly terrifying weapon," judge Douglas Trapnell said.
"It has no use other than a mass killing machine and has no place in civil society."
Munro paid about $US1000 per assault rifle and $US2000 for some of them to have their serial numbers or identifying marks removed.
Back in Australia, Munro was arrested at Geelong on August 30, 2016 after he set up a deal to sell 15 firearms for $110,000 to an undercover operative.
The mechanic was selling the Thureon rifles for $15,000 a piece, and charging $5000 for handguns.
Before Munro was arrested, a local gun dealer warned the mechanic about selling illegal guns to people he didn't know.
The dealer advised Munro not to trust people who want to do business without a personal recommendation.
Judge Trapnell said police are yet to recover 40 firearms and firearm parts that Munro smuggled into Australia, including five Thureon fully-automatic machine guns.
Three Thureon machine guns were seized at Caroline Springs, Williamstown and Rockbank as police charged three men with trafficking a commercial quantity of methamphetamine.
A fourth Thureon weapon was handed into police as part of a gun amnesty.
Judge Trapnell said Munro ran his "nefarious scheme" to support his lifestyle after various failed stints in farming and car restoration.
Munro pleaded guilty to four charges of importing firearms and two counts of attempting to import firearms.
He was sentenced to 10 years and three months in jail and has already served 617 days in pre-sentence detention.