Bomb disposal experts carried out a controlled explosion and a man was arrested on suspicion of possessing a firearm following an incident in West Kirby.
The incident led to a number of roads being closed and people evacuated from their homes.
A section of Leigh Road remains closed today after the device was detonated on yesterday [Wednesday] afternoon.
The incident is now subject to forensic investigation.
The 51-year-old man is believed to be from the Derbyshire area and was arrested on suspicion of possession of a firearm after a motorist reported having been threatened with a handgun in Victoria Road after a brief dispute.
His car was searched and a suspected air weapon was seized.
Concerns were raised about a number of other items in the car, a cordon was put in place as a precaution whilst specialist search officers were called.
Residents living nearby were also advised to stay indoors.
Police say the incident is not believed to be terrorist-related.