Acting on a tip off, the STF and local police, in a joint operation, raided a house in Gosain Bigha village and found the factory, DSP Shaharyar Akhtar said.
Two dozen barrels, three semi-processed pistols and many equipment used for processing weapons were seized from the unit, he said.
Three persons, identified as Mewalal Vishwakarma, Pradesh Vishwakarma and Rajiv Vishwakarma were arrested from the spot.
Mewalal has been arrested and jailed in the past too for processing illicit weapons and was out on bail, the DSP said.
