48-year-old Evan Girdlestone from Colliers Wood was arrested by officers from the NCA’s Armed Operations Unit in May last year as he approached his parked car in Croydon.
Hidden under the passenger seat of the car was a converted gun with two magazines of ammunition.
Girdlestone had an industrial unit in Wimbledon which he used as a production line for the conversion of top-venting blank firers into lethal weapons.
NCA officers performed a toothcomb search of the unit and found converted weapons, imitation firearms, 174 rounds of live ammunition, a quantity of spent ammunition and multiple tools used to convert blank firers.
In total Girdlestone was in possession of four converted guns and four unconverted blank firers.
Girdlestone had also test fired his converted weapons at the unit shooting through phonebooks attached to a concrete wall.
He messaged associates about being injured by a ricochet.
The AOU investigation began in April 2023 with assistance from the NCA’s National Firearms Targeting Centre, which develops the national intelligence picture on guns.
Over a series of appearances at Croydon Crown Court, Girdlestone admitted: four counts of possessing firearms, three counts of possessing ammunition (174 rounds of varying calibres) and three counts of converting blank firearms.
Debbie Palmer-Lawrence, head of the NCA’s Armed Operations Unit, said:
“As an armourer, Girdlestone was reckless and a real danger to the public.
“He is now in the right place after excellent work by a variety of NCA teams to build the rock solid case against him. He had no choice but to plead guilty.
“Tackling the criminal use of firearms is a key priority for the NCA and we work with partners at home and abroad to do everything in our power to protect the public.”