are you needing to follow gamebore advice on cleaning the gun?
Specialist Cleaning Instructions:
Spray a mild, water-based household cleaning product such as glass cleaner down the barrels, leave for a few minutes to allow the breakdown of any stubborn dirt or residue. Next use a wire brush to remove the fouling, followed by a cleaning mop or cloth to wipe away the excess. Dry the barrels thoroughly before applying a gun oil.
As with any type of cartridge; barrels and chokes should be cleaned after each use to avoid buildup of residue.