Passionate gun collector and firearms licence holder Roy Bennett, aged 71, was given a five-year sentence for possessing illegal firearms recently.
Bennett was living in a farm cottage, near Rochdale, when he amassed the guns.
He pleaded guilty to nine firearms offences at Bolton Crown Court.
A passionate gun collector, Bennett said he found one of the shotguns in the attic of his house when he moved in, and bought another at a car boot sale for just £1, where it was being sold as a cigarette lighter.
He had also built a miniature cannon himself and police were alerted to its existence when he fired it at a local gun club.
A Greater Manchester Police’s firearms officer said it “sends out a very clear message to firearms and shotgun certificate holders”.