Christopher Paul Mannion, aged 59, pleaded guilty to not having a certificate for the shotgun which was found under the master bed at his former partner's home after police were tipped off.
The court was told that Mannion, who had been arrested by officers, is a lorry driver who "lives in his cab" and his address was given as his mother's home in St Martin's, near Oswestry.
Prosecutor Hannah Baddeley said Mannion had a licence granted in Essex in 2008 that had expired. He had used it to shoot "clay pigeons and animals", the court was told. He had moved to the area five years ago.
"He had been trying to sell it for ages by word of mouth but unsuccessfully," the prosecutor said.
The court was told that Mannion had no objection to the forfeiture of the shotgun, that he was not at home very often and there is no suggestion that the shotgun had been used in a threatening way.
The three magistrates sitting on Tuesday fined Mannion £166 and ordered him to pay £185 costs and a victim surcharge of £34 after being told he had a weekly income of £500 per week.
Presiding justice David Silcock said: "You are free to go, sir."