+1 Clean chamber well; I use an over sized thick, heavy brass wire brush on an extended shaft with an electric drill. Hoppes seems to do the trick well.
Make sure the extractor grove is clean, too. Take the bolt apart and soak it in gas; I use just enough in a heavy ziplok, to shake it up. The guide is a tool for unscrewing the firing pin; note the position of the alignment notch on the safety knob face before disassembly.