The raid took place on Saturday evening, as a chapter of the biker gang was celebrating its tenth anniversary at its headquarters in Ulvsunda, northern Stockholm.
Some 40 police officers were involved in the raid, which was launched after a tip-off that illegal drugs were being kept on the premises.
As well as finding drugs, the police discovered a 120 kilogram tank gun. The weapon was Swedish-made, and of a type no longer used by the Swedish army. No ammunition was found on the premises.
