The online sale of an accessory that turns a handgun into an automatic weapon has raised concerns in Australia.

Key points: A man has been fined for buying two selector switches that would have converted his pistol into a machine-gun

A man has been fined for buying two selector switches that would have converted his pistol into a machine-gun The device allows consecutive bullets to be fired without the shooter having to let go of the trigger

The device allows consecutive bullets to be fired without the shooter having to let go of the trigger The man never used the switches and his lawyer argued they were bought out of curiosity

A West Australian man was fined almost $13,500 on Monday for buying two selector switches for his Glock pistol from the online retailer eBay.

The device would have allowed Albany man Michael Gregory Page, 47, to convert his firearm into a machine-gun.

WA Firearms Traders Association president Bevan Steele said Page — who was described in court as a member of his local pistol club — should have known better.

"There's a reason why you don't find them [selector switches] on shelves in shops, because they are illegal," Mr Steele said.

"Firearms retailers and manufacturers will not have these products.

"We know what the legislation allows us to do and what it does not allow us to do."

YouTube videos from the US demonstrate the machine-gun-like capabilities of modified Glock handguns. ( YouTube: Royal Range USA )

Modification turns handgun into machine-gun

A selector switch allows a pistol to fire consecutive bullets without the user having to let go of the trigger.

They are illegal in Australia but appear to be available for sale from international websites for as little as $24.

There are also numerous YouTube videos demonstrating the effect of making the modification to the common Glock pistol.

Mr Steele said safeguards were in place to prevent the importation of selector switches, particularly if they were purchased from the United States.

"Most places in the US already have a mandated restriction, so as soon as you push 'shipping' into Australia it raises a red flag in their area and they know not to ship it," he said.

Information received by Border Force led to the arrest of Page, who paid less than $50 for the two selector switches ordered between September 2018 and January 2019.

A photo from a website that appears to be offering a Glock selector switch for sale. ( Supplied )

Heavy fine reflects severity of the crime

The switches were never used and Page's lawyer argued they were bought out of curiosity.

However, Magistrate Raelene Johnston disagreed and said although Page had no previous convictions, the sentence must set an example for future offenders.

Mr Steele said such instances often painted the gun community in a negative light.

"Hopefully most people see through whatever this individual has chosen to do and see he's only one person in a club of thousands and thousands of people out there that are doing the right thing on a daily basis," he said.

The Glock is a popular handgun, Mr Steele said, that is widely used by gun clubs around Australia.

While it has been dubbed a weapon of choice for mass shooters in America, it is also the standard issue firearm for WA Police.

WA Police Great Southern District Superintendent Ian Clarke said Australia had "extremely strict" handgun ownership laws, but online sellers presented an ongoing challenge.

"Putting something like that [a selector switch] on a handgun is reckless in one aspect, but it's a significant lack of respect for the broader community," he said.