Home airsoft repair?

Has anyone else ever done this before? Right now i'm trying to repair an m4 and some random rifle with only a little success.

Advice? Stories? Experiences?

I have torn apart and tried to repair a few, the main problems are they are made from plastic and pot metal which does not lend itself to repairs.

If you gave more detailed explanations of the problems and even a few pictures with circles and arrows that would give me something to wrap my brain around.

will post more with pictures later this week when im not busy

edit: make that sometime this month...