Acting on a tip-off, police raided a house where arms were being manufactured at Puralsi village under the jurisdiction of Budhana police station, circle officer Mohanlal said.
Police seized 20 pistols and 50 others in manufacturing process. The machine used to make guns was also seized.
Four accused, however, were managed to escape.
A case was registered against four persons including Dilshad and Nisar who are absconding.
It was revealed that the unit was supplying arms to be used during the upcoming assembly elections, police said.
The illegal gun factory was functioning from Shahpur town, police said.
Assembly elections in Uttar Pradesh will be held from February 11 to March 8 in 7 phases.