I have a P7M13, which I purchased used. It's great, but lately has been having some reliability problems which I believe are due to dirty gas port equipment (ie, the chamber and the plunger, are those the terms?). Anyway, I don't have the cleaning tool, but I would like to know the best way to clean the gas chamber and plunger. I'm remember someone mentioning a 7mm brass brush. What should I use, and how should I do it?