Owners of particular types of blank firing guns, which have become popular with criminals, have been urged to hand the firearms in to police stations after tests found they can be easily converted to fire live ammunition.

The National Crime Agency (NCA) highlighted four brands of blank firing guns, originally designed to fire blank ammunition without a bullet or projectile component, which are “readily convertible” and therefore illegal under the Firearms Act 1982.

The specified brands are the Turkish models of top-venting blank firers (TVBFs) Retay, Ekol, Ceonic ISSC and Blow, and the NCA said they were used in at least four killings in the UK in the last two years.

According to the agency, UK law enforcement has recovered 800 of the guns converted to fire live ammunition since 2021 and the number of discharges last year from TVBFs outnumbered those of “original lethal purpose” (OLP) firearms – 64 compared with 42.

An amnesty will be held in England and Wales February 3-28 next year for owners to hand in the firearms at police stations across the two countries.

Possession of one of the guns after the amnesty period could result in a prison sentence of 10 years.

People can also hand them in before the amnesty begins without risking prosecution.

The NCA and police chiefs performed tests, funded by the Home Office, of the four gun models in March and April.

The results showed they were readily convertible with “common DIY tools” and without the need for any “specialist skills”.

TVBFs are legal to buy in the UK without a licence by over-18s unless they are readily convertible.

Stopping the sale of these guns will go a significant way to help protect the public

In their original state, they have a fully blocked barrel and are designed to discharge only blank cartridges.

They are sold with at least half of their visible surface painted a bright colour, but criminals have been painting them black to make them look like OLPs, according to the NCA.

Assistant Chief Constable Tim Metcalfe, from the National Police Chiefs’ Council (NPCC), said: “These firearms are very appealing to criminals and offenders who convert them can generate large profits.

“During the last two years, policing and the NCA have identified and disrupted several workshops used to convert these pistols into lethal weapons.

“In the same period, large numbers of converted weapons were recovered across multiple locations, alongside thousands of rounds of blank calibre and modified ammunition.

“One investigation recovered more than 400 converted weapons from a single crime group. There is a strong demand for them evidenced by the numbers imported and subsequent recovery from criminals.

“Stopping the sale of these guns will go a significant way to help protect the public.”

The four brands “overwhelmingly” account for the number of TVBFs in UK circulation, the NCA said.

Dangerous criminals will always look for new ways to acquire weapons, but we remain vigilant in taking them out of their hands

Importers and traders have been informed and told to stop trading them, and Border Force will seize further importations of the specified models.

Policing minister Dame Diana Johnson said: “Dangerous criminals will always look for new ways to acquire weapons, but we remain vigilant in taking them out of their hands.

“These weapons are illegal and it is vital any member of the public possessing these blank firers hands them into their local police station.

“We will continue to keep the legislation on dangerous weapons under constant review to react to new threats and support police to make our streets safer.”

NCA deputy director, Charles Yates, said these converted guns pose a “significant threat” and that it is “crucial” to prevent further access to the “easily converted” firearms.