The monitoring of 3D printer sales may need to be bolstered in the future to prevent the illegal manufacture of imitation firearms, NSW Police have suggested.

A 27-year-old Sydney man on Tuesday became the first person in NSW to be charged with possessing blueprints to manufacture firearms after detectives raided his Bronte apartment.

Sicen Sun was granted bail on Wednesday after Waverley Local Court heard he was "something of a fanboy" who allegedly made the guns to resemble those in TV shows and games like NCIS and Call of Duty.

But Detective Inspector Joe Doueihi, of State Crime Command's Firearms Squad, said imitation firearms were treated just the same as the real thing under the law.

"He just took it that extra step," Det Doueihi told reporters in Parramatta.

"That's no defence in the current law, he's committed a serious criminal offence and that's why he's before the court."

The detective said Sun faces maximum sentences of 20 years for manufacturing a firearm and 14 for possessing the blueprints.

Police were tipped off to the 27-year-old's activities after he advertised a weapon for sale on social media with an asking price of $1 million.

Det Doueihi says online sales are an "emerging trend" and the use of 3D printers to create weapons is an ongoing concern.

"The technology is there, it is available, and if you had the appropriate skills and the appropriate equipment you could make a fully-operational firearm," he said.

Asked whether the sale and use of 3D printers needed to be monitored more closely, Det Doueihi said it was a difficult area.

"These machines are used for all other purposes in the world - science, industry - (but) perhaps that is something we could look at down the track," he said.

Police allegedly found four imitation pistols, two air pistols, computer equipment and two 3D printers at Sun's property.

A magistrate granted him bail on the condition he surrender his Chinese and Australian passports, stay away from international airports, and pay a $3000 surety.

He's due to face court again in April.