The STF also recovered Rs 7,400 in cash and a few mobile phones from their possession.
Officials said the apprehended persons supplyied ammunition of 7.62 mm to various gangs across the state.
All of them are being interrogated for further information.
In another operation, the STF arrested two ganja smugglers Deepak Kumar Singh and Manoj Kumar from Barari in Bhagalpur district and recovered 180 kilograms of the narcotics from them.
Both are residents of Dhanbad in Jharkhand and had come to Bihar to supply the contraband.