Armed officers swarmed on Diplocks Way as Sussex Police and the National Crime Agency investigated an incident close to the the Hailsham by-pass.
The agency, which combats serious and organised crime, said two firearms were recovered at the scene.
Three men were arrested on suspicion of firearms offences and are currently in custody.
NCA deputy director Chris Farrimond said: "As a result of this operation two firearms have been recovered and they will now be the subject of analysis. "Our investigation is ongoing, and we are working very closely with our partners at Sussex Police as it progresses."