A man found allegedly harbouring firearms, and more than 2000 rounds of ammunition, swords, knives and crossbows in Sydney's west has been placed in a mental health facility for assessment, police have said.

They also found ballistic vests, armoured helmets, ballistic face marks, handcuffs, more than 100 arrows and "terrorism response" books written by "famous snipers", after executing two search warrants at the Richmond home last Tuesday.

The 64-year-old man was arrested by police who were acting on a tip from the Australian Border Force about firearm parts being imported into the country.

Ballistic face masks and vests, as well as armoured helmets, were discovered by police. ( NSW Police )

"We've got no direct information of what this individual intended to do" with the weapons, said Stuart Smith, NSW Police's Acting Commander of the State Crime Command.

"We can only interpret the evidence from the scene, and [he was] obviously a deeply disturbed individual who was highly trained with military grade weaponry and reading material … coupled with ballistic protection," he said.

"The threat was real, it was significant, and it was imminent."

Police said the man used to be prisoner officer who had weapons training and was dismissed by corrective services.

"We remain vigilant in terms of our inquiries," Mr Smith said.

"We have to accept we are conscious of what is happening around the world and the NSW Police are here to mitigate the risk.

A man in Richmond, NSW, was found with military grade firearms, swords, knives, crossbows, ballistic protection, literature on weapons, and 2000 rounds of ammunition. ( Supplied: NSW Police )

"What we found is … a deeply troubled individual.

"With the literature in the house, we were obviously concerned that this person posed a significant risk to the community."

Police said the man showed signs of mental health issues, and family members who lived in the house cooperated fully with authorities.

Mr Smith said the case was referred to the state's Drug and Firearms Squad and not counter-terrorism authorities because it "was in relation to a transactional inquiry by the individual … buying tactical equipment and firearms accessories."