Haroon Iqbal, 32, from Birmingham, used parts he ordered on the dark web to create viable guns and was nabbed by the security authorities who set up a surveillance operation.
He first requested internal parts of a Glock 17 weapon from a seller along with electronic items, using a different identity. This order was intercepted on arrival in the UK on January 22 and the parts discovered.
Although the items were not illegal on their own, they were forensically marked by National Crime Agency (NCA) officers and delivered to an address in the city on January 24. When the defendant collected the order investigators were watching and the parts were recovered when Iqbal was arrested the following month.
The vendor who was based in the United States was also arrested by US Homeland Security agents and his mobile phone seized.
Messages found on that device using the encrypted messaging service Signal showed that Iqbal had asked whether the seller had ever had a shipment seized, and requested that a Christmas card was added to the package as a decoy in order to make it look legitimate.
Then on January 26 he requested a Glock 17 barrel and automatic rifle parts which were hidden inside a toolbox, telling an undercover officer who was now using the seized phone how to pack the second load and providing a UK phone number for it.
But the US authorities organised for the toolbox without the barrel or rifle parts to be sent to a second address in Birmingham.
Following the delivery on February 28 officers arrested Iqbal. The phone with the number used on the parcel was found in his car, and officers seized a 3D printer and an ammunition press from his business premises.
Officers also found the internal parts first sent to Iqbal in January which had the forensic markings.
Iqbal, of Bramble Dell, Bordesley Green, previously pleaded guilty to attempting to possess a firearm at Birmingham Crown Court. He was jailed for 27 months on Thursday.
NCA operations manager Niall Conner said: “Haroon Iqbal spoke with supreme confidence to someone he thought was a seasoned gun supplier in the US, giving detailed instructions to ensure he would receive the orders to the UK. His plans were stopped when US authorities arrested his contact and took over communication with Iqbal as he sought to arrange another delivery.
“Our investigation has taken items including gun parts and a 3D printer out of circulation, which could have been used to create deadly weapons for use by organised crime groups.
“The supply and use of firearms has a devastating impact on public safety and are used in acts of intimidation and serious violence. We will continue our work to stop those who are intent on bringing illegal firearms to our streets.”