NSW police say NSW Highway Patrol officers stopped the man for a roadside test for drugs and alcohol on the Illawarra Highway near Robertson about 5pm.

No alcohol was detected in the roadside test but the driver returned a positive result from the drug screening test.

Police then searched the vehicle where they allegedly found prohibited drugs, nunchuks, a baton, a large amount of pistol ammunition, and the 3D-printed firearm.

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Police said they seized the items, which will undergo further examination.

Inquiries established the man held a valid firearms Category A or B licence, but this did not entitle him to have pistol ammunition or the pistol.

The man was arrested and taken to Southern Highlands Police Station where he was charged with 11 offences, including two counts of possessing a prohibited drug, possessing a loaded firearm in a public place, not storing a firearm safely, and possessing an unauthorised pistol.

Police also suspended his firearms licence.

The seizure of 3D printed firearms is relatively rare in Australia and the Australian Criminal Intelligence Commission, in its most recent report on illicit firearms five years ago, found that "currently, the technology does not commercially enable the mass production of printed components that match the reliability and cost-effectiveness of factory-produced firearms".

However, advancements in the technology in recent years means 3D printers can be purchased for as little as $500.