Officers searching Paul Donnell's home in Erskine discovered five handguns, a rifle and live ammunition as well as heroin and cocaine worth tens of thousands of pounds. Drugs used as mixing agents were also found in the flat.
Donnell pleaded guilty to being concerned in the supply of cocaine and heroin and possession of prohibited firearms and ammunition.
The 43-year-old was sentenced to nine years and four months in prison when he appeared at the High Court in Glasgow yesterday.
Lindsey Miller, Head of the Serious and Organised Crime Division (SOCD) of the Crown Office and Procurator Fiscal Service, said: "Paul Donnell was found with significant quantities of illegal drugs, as well as substances associated with selling them on a large scale. He was also found with a number of illegal firearms and ammunition in his flat.
"The authorities in Scotland take drug dealing and firearms offences extremely seriously indeed, and recognise the potential harm that can go alongside such a toxic mix.
"Fortunately, due to the swift actions of prosecutors and police, Donnell has been brought to justice, his drug dealing business dismantled and his weapons taken out of criminal circulation."