Gunsmith's converted replicas used in 52 shootings

An underworld gunsmith who modified replica machine guns in a garden shed "factory" – weapons which were used in a surge of shootings and murders, including the killing of PC Sharon Beshenivsky in Bradford in 2005 – could be jailed for life after being found guilty of firearms offences.

Grant Wilkinson, 34, bought 90 blank- firing Mac-10s from a registered gun dealer, claiming they were to be used on the set of a new James Bond film. Instead he turned them into some of the most lethal weapons seen on the streets of Britain in recent years, many of them ending up in the hands of inner-city teenage gunmen. Police have yet torecover half of the weapons.

A jury at Reading Crown Court heard that the guns were highly prized by organised criminals not just for their "bling" value, but also for their ability to disperse 9mm bullets rapidly across a wide target area of up to 50 yards, earning the weapons the nickname "spray and pray".

Between 2004 and 2008, the weapons were used in 52 shootings in London, the Midlands and Manchester, resulting in eight murders.

Among the victims was 15-year-old Michael Dosunmu, who was killed as he slept at home in Peckham, south-east London, last year. The dead boy's father, Rasak Dosunmu, 51, said yesterday that Wilkinson was as responsible for his son's death as his killers. "You are talking about blood money – this is not a legitimate business or legitimate money," he added.

The appearance of the guns on the black market resulted in what detectives described as a "sea change" in criminal firepower. It began when Wilkinson, using a false a name, bought the Mac-10s, with 25-round magazines, from Sabre Defence Industries in Northolt, west London. He paid £55,000 in cash.

Shop staff became suspicious, despite his claim that they would be used in the filming of the next 007 movie. He was photographed on his final visit, although police were unable to identify him from the image.

The gunsmith turned the guns into live firing weapons in a garden shed in Berkshire. They were then tested at a sound-proofed house and put through their paces at a backyard firing range at the derelict house in Three Mile Cross, near Reading.

When the shabby premises were eventually raided, police discovered gun modification being carried out on an unprecedented scale. Wilkinson masterminded the sophisticated operation using expensive industrial equipment used to smelt and cut metals. The weapons were sold as a package, complete with bullets, for between £1,500 and £2,500. Some 27,700 spent cartridges that could be reconfigured into live ammunition were also recovered.

Wilkinson was convicted of a series of offences including conspiracy to convert an imitation firearm into a firearm, conspiracy to sell or transfer firearms and ammunition and possession of a firearm. His co-defendant, Gary Lewis, 38, of Bourne End, Buckinghamshire, was cleared of all charges against him.

The victims of Wilkinson's handiwork

* 18 November 2005: PC Sharon Beshenivsky shot dead outside a travel agency in Bradford. Mac-10 discharged at the scene. Somalian Yusuf Jama, 20, convicted of murder.

* 18 July 2006: Jason Greene, 29, ambushed by gunmen who shot him dead in front of his children in Wembley, north London. Christopher Toussaint-Collins, 19, convicted of murder.

* 20 October 2006: Antoine Smith, 24, shot dead by two attackers on bicycles in south-west London. Two teenagers acquitted of murder.

* 1 November 2006: Jamail Newton, 19, shot dead in Camberwell Green, south London, by two gunmen armed with Mac-10s, including a gun used to kill Mr Smith in October.

* 2 February 2007: Michael Dosunmu, shot dead while asleep in Peckham, south-east London. Mohammed Sannoh, 19, and Abdi Omar Noor, 22, convicted of murder.

* 27 July 2008: Curtis Smith, 36, shot dead outside Red nightclub in Limehouse, east London.