Police have found a massive arsenal of semi-automatic rifles, crossbows and hundreds of knives and swords at a home in Sydney's west belonging to a former corrective services officer with high-level weapons training.

Detectives who were executing a search warrant at the home in Richmond found five rifles, including a semi-automatic Norinco SKS, more than 2000 rounds of ammunition, three crossbows and more than 100 arrows, a large collection of knives and swords and literature relating to terrorism and disaster response protocols.

Seven tactical police officers arrested a 64-year-old man at the home while he was taking out the garbage and found five knives on his person, Acting Assistant Commissioner Stuart Smith said.

The man was taken to Windsor police station where he "developed quite acute behaviour" and was taken to hospital for a mental health assessment, where he currently remains.