A self-confessed "ammunition freak" has been found guilty of supplying illegal handguns and home-made bullets used or found at more than 100 crime scenes, including three murders.
Arms dealer Paul Edmunds, 66, imported weapons from America as well as fixing up antique guns and making thousands of bullets at his home in Glocestershire.
One Colt pistol he imported was used in a fatal shooting at a London nightclub, and he supplied ammunition used in two other killings and an attempt to shoot down a police helicopter.
Despite the killings carried out using weapons he sold, Edmunds told police he "didn't give a s***" about potential victims, adding he was "not responsible for the actions of somebody that buys some things".
A jury at Birmingham Crown Court was told that Edmunds, of Bristol Road, Hardwicke, was arrested in 2015 at his home, where he had three armouries and made bullets to fit antique weapons.
The registered gun-dealer was also convicted of possessing a prohibited air pistol and perverting the course of justice by filing down a bullet-making tool to destroy potential evidence.
A retrial was told that Edmunds and middleman Dr Mohinder Surdhar - likened by police to the lead characters in TV series Breaking Bad - acted together to supply antique revolvers and custom-made ammunition to criminal gangs.
Edmunds sold the weapons and cartridges to Surdhar, who fenced them on to a crime gang armourer, Sundish Nazran.
Detectives said the seizure of 50,000 rounds of ammunition and guns imported or brought back into service by Paul Edmunds was a "major victory" on gun crime, which had undoubtedly saved lives.
But while 17 pistols criminally-linked to Edmunds have been taken out of circulation, police said of the 280 guns imported between 2009 and 2015, the whereabouts of 207 remain a mystery.
Meanwhile, officers have also recovered about 1,000 of his hand-crafted rounds from crime scenes, but shells are "still coming in" more than two years after Edmunds' arrest.
He side-stepped UK laws on importing old guns for which ammunition was commercially available by falsely declaring to the authorities in customs paperwork they were obsolete "antiques".
The guns, whose importation is subject to complex rules, were not checked in any detail at UK customs.
Trial judge Richard Bond described how he had been "aghast to hear evidence of one dealer being waved-through on occasion by customs at Heathrow".
Edmunds made 37 trips to the United States, checking the guns into airlines' holds as "antiques and curiosities".
He was remanded in custody to be sentenced on December 20.
- Scenes of killings where Edmunds's weapons were found
The weapons and ammunition have been directly linked to crimes across nine police forces.
A 1920 Colt pistol supplied by Edmunds was used in the fatal Boxing Day shooting at the London Avalon nightclub, in 2013.
One round of unfired ammunition was found on the ground at the murder scene of 18-year-old Kenichi Phillips, who was shot dead in a Birmingham street in March 2016.
The teenage killer, Disharn Downie, who was 17 at the time of the murder, fatally shot Mr Phillips after a "brief exchange of words".
He was jailed last year for a minimum of 21 years.
Another gun, again linked to Edmunds, was also found to have been fired at the scene of another fatal shooting in the city in October 2015.