Police found a sawn-off shotgun after a dramatic operation in Southampton linked to blackmail in the drugs underworld.
The pump-action firearm was found complete with cartridges in the boot of a car parked near a property in Cranbury Road.
Michael Foster had pulled up in the car and an undercover police team finally swooped after witnessing people moving between the vehicle and the building they were monitoring.
The 26-year-old was arrested during the covert operation, which involved up to 40 officers.
He denied knowing that the gun was there but a jury found him guilty after a three-day trial and now he is starting a five-year jail term.
Portsmouth Crown Court heard how Foster had travelled from Banbury in Oxfordshire to deliver the shotgun to “known criminals” in Southampton in September last year.
Detectives say the operation was part of an undercover investigation into blackmail linked to drugs which resulted in a total of 12 arrests.
Det chief Insp Dick Pearson said: “Our Major Investigation Team includes the force’s Serious and Organised crime Unit. This was involved in investigating a potential blackmail offence, which was connected to drugs.
“Specialist officers from the unit were focused on ensuring the safety of people affected by these circumstances.
“Between September 7 and 8, 2011, officers kept an address under observation.
Our covert monitoring resulted in 12 arrests, including Michael Foster.
‘Foster was prosecuted after a firearm was found in a car linked to him.
‘The Hampshire Major Investigation Team has dedicated experience and expertise to investigating information and crimes involving firearms, particularly when there are risks to people’s safety and drugs-related violence.”