As zooma said, check the breech seal is not "dry" or distorted and, on a PCP, check that any seal between the cylinder and the frame of the pistol has not been damaged for lack of lubrication. Feinwerkbau provide a light grease which seems to work well.

It might be worth running a chrono check - around 4 - 4.5 ft lbs and 500 ft/sec with a 7g pellet should be OK for 10 metre work.