Gun and shooting clubs have raised concerns after Devon and Cornwall Police revealed it had fallen far behind processing thousands of shotgun licence transfers.
Following a Freedom of Information request by the Western Morning News, the force admitted that as of September 17 it had around 6,250 gun transfer amendments which had yet to be added to its electronic records.
Each time a shotgun is bought or sold, both the seller and the new owner are obliged to register the weapon with the police, informing them of their licences and what weapons they already hold.
But some gun owners claimed the records held by police were months, on some occasions years, out of date.
One Devon shotgun owner, who asked to remain anonymous, said: "I was recently checking on my records and found the police still had a gun I sold nearly two years ago next to my name.
"It's very worrying to me that they effectively didn't know who owned which guns."
Devon and Cornwall Police claimed the paper-based notifications of guns that have been sold on to other people were "held in a format that is easy to search should they be required for accounting purposes".
The force said there were 30,798 shotgun certificate holders in the area – a number that changes "daily" – and its aim was to renew certificates before their expiry date.
It insisted there were "no backlogs in this area of work". However, it accepted it had fallen behind on paperwork that noted which guns had been bought and sold to other licence holders.
A police spokesman said: "On average, the force received around 50 gun amendment requests every day and these and the other outstanding transactions are being processed as quickly as possible.
"The paper-to-electronic process in place does not increase the risk to the public and it is estimated that all transfer notifications will be moved to the electronic record some time in October.
"The cyclical nature of shotgun renewals means there have been peak periods of high demand for certificates and this by its very nature has contributed to the outstanding work we are addressing."
The force also admitted that the Firearm Licensing Unit had been "under constant scrutiny as part of normal management practices" and that "measures were taken to improve efficiency in processing large volumes of applications for renewals in particular".