According to details of the case, Mr Randhawa had tried to buy a Vehicle Borne Improvised Explosive Device (VBIED), a remote-detonated explosive device from the 'dark web'. He is due to be sentenced on January 12 next year.
Mr Randhawa, who has been remanded in custody, was convicted of maliciously possessing an explosive substance with intent to endanger life or cause serious injury at Birmingham Crown Court this week. "The explosive device Randhawa sought to purchase online had the potential to cause serious damage and kill many people if he had been successful in using it," said the NCA's Tim Gregory.
"He was not involved in an organised crime group or linked to terrorism, but is clearly an individual who poses a significant risk to the community.
"Identifying people like Randhawa - who seek to access illegal firearms and weapons - is a priority for the NCA and we will not stop in our efforts to make sure they are arrested and held accountable for their actions," he said.
Two women - aged 45 and 18 - were also arrested at the same time by the NCA Armed Operations Unit but were later released with no further action.
Mr Randhawa had previously pleaded guilty to attempting to import explosives but was found guilty of the more serious charge of maliciously possessing an explosive substance with intent to endanger life or cause serious injury.