A firearms dealer manufactured and supplied home-made ammunition found at over 90 crime scenes including fatal shootings, a court has heard.
Prosecutors said Paul Edmunds used his "almost encyclopaedic" knowledge of firearms laws to smuggle hundreds of guns which he sold on illegally.
"Tell-tale" marks on ammunition linked the rounds to Mr Edmunds, they said.
Mr Edmunds, 65, of Hardwicke, Gloucestershire, denies conspiracy to supply firearms and ammunition.
At the start of Mr Edmunds' trial at Birmingham Crown Court, prosecutor Andrew Fisher QC told jurors the defendant had been supplying large quantities of weapons to a gang via another gun dealer.
He also supplied "what most ordinary people would call a bullet" Mr Fisher QC alleged, referring to a complete round of ammunition.
'Armoury in garage'
He told the court there was a "well-known" black market for "antique" weapons and specially-made rounds because of a legal loophole exempting them from a handgun ban passed in 2007.
The "going rate" for these weapons and a supply of rounds was about £3,000, Mr Fisher said.
From about 2009, Mr Fisher QC said, police had noticed an increase in the use of pre-war handguns - for which bullets were no longer commercially produced - from crime scenes.
Ballistics experts analysed ammunition found at the scene of several fatal shootings and the targeting of a police helicopter during riots in 2011, the court heard.
They found markings "like fingerprints", the court heard, which suggested they had all come from the same supplier.
Mr Edmunds was arrested in July 2015, and when police searched his home they found "three separate armouries", Mr Fisher QC said.
"The principal one was in his garage, the police discovered a second one in a bedroom and a third one which was more of a store in the attic," he said.
"There were many tens of thousands of rounds of ammunition and component parts."
After police seized numerous guns from Mr Edmunds' property, the court was told, examination of his firearms registers revealed he had made multiple false entries.
Mr Fisher said: "He has used his knowledge and status as a registered firearm dealer, to get round the legislation controlling firearms and, it has now become clear, has been supplying guns and ammunition wholly unlawfully for many years."
Mr Edmunds, of Bristol Road, Hardwicke, denies conspiracy to supply firearms and ammunition, transferring prohibited weapons, possessing a prohibited air pistol and perverting the course of justice.
The trial continues.