A man has been charged with unlawfully possessing ammunition after being arrested on a train between Penrith and Parramatta on Wednesday.
At about 2.30pm, Wednesday, officers allegedly found 21 rounds of ammunition on the man after he failed to produce a valid ticket.
He was also in possession of a petrol-powered bicycle which is prohibited on trains.
Police later charged the 36-year-old man at Parramatta police station.
He appears in Parramatta Local Court on August 13.