The police acted on a tip off and Mohammad Monu was arrested from the taxi stand area, Superintendent of Police Varun Kumar said.
Two dozen automatic pistols, an ATM card and a driving license were recovered from Monu, a resident of Hazratganj locality of Munger town.
During questioning, Monu said he had been working as an arms carrier for one Mohammad Mahtab, a resident of Maksudpur in the district, who has set up a factory in Malda district of West Bengal for manufacturing arms illegally, the SP said.