Acting on a tip off, the Rabindranagar police station personnel raided a rented house in Mollahpara in south Kolkata and found the arms and ammunition.
"We have seized nine 7mm pistols and 22 9mm pistols from the house. Plenty of ammunition, gun making ingredients and machines were also seized," police said.
However, the persons involved in the illegal arms production could not be arrested as the owners said they have left the house three months ago.
Police have arrested house owner Samser Ali for interrogation.
"We were not aware of the arms production. Five people from Bihar rented our house to run a factory six months back but they were not satisfied with the facilities and said they would leave," said Ali's wife.
"They were supposed to take away their machinery but never came back," she added.
The tenants reportedly have taken innovative steps to make the house sound-proof.
"The room windows were mounted with pitch boards so that the sound of led machines does not go out. Also loud music was played in the house to camouflage the machine noise," police said.
Earlier this year, two more illegal gun factories were busted by the police in Mahestala and Baruipur in south Kolkata, where they seized a number of improvised small arms including one-shotters and single barrel guns.
Police said they are on the hunt for the five accused.
