Ninety guns have been seized by detectives who say they have smashed a major firearms conversion operation in south-east London.
Ninety guns were
A house in Wickham Lane, Plumstead was searched by armed police at 0300 GMT on Thursday following a tip-off from the National Criminal Intelligence Service.
Officers suspect gas-fired replica guns were being converted at the building to fire live ammunition.
Forensic teams are examining the scene, where stun guns and CS gas canisters were also found.
Hydroponics equipment which can be used to grow cannabis was also found.
Assistant Commissioner Tarique Ghaffur, head of the Specialist Crime Directorate, said he believed the weapons were going to be sold to London criminals.
"The devastating impact they would have had on the communities of London cannot be overestimated," he said.
"We will continue to target those people involved in armed criminality and additionally those individuals responsible for placing the weapons in their hands".
On Wednesday, a cross-party group of MPs called for a total ban on the manufacture and sale of replica guns.
A 35-year-old man has been arrested and is being questioned.