The PSNI say they are looking into the find in the Sharman Road area of south Belfast.
Detective Sergeant Keith Wilson said “At 1.10 pm police received a report that the firearm had been found on a pathway near to the Lagan Towpath beside Sharman Road in Belfast. The item has been taken away for further examination.
“Anyone who knows anything about this item, or who may have noticed any suspicious activity in the area recently, is asked to contact Musgrave Police Station on the non-emergency number 101, quoting reference number 494 of 21/03/17.
“Or if someone would prefer to provide information without giving their details, they can contact the independent charity Crimestoppers and speak to them anonymously on 0800 555 111.”