Gardai are continuing to question a man after the discovery of a loaded sub-machine gun in Lucan.
Ammunition was also found in the Balgaddy area on Sunday evening. It's reported the gun was found buried in the back garden.
The raid was carried out by detectives from the Garda Drugs and Organised Crime Bureau.
A 20 year old man was arrested during the operation.
He's being held at Ronanstown Garda Station where he can be held for up to 72 hours.