I have a 4 month old baby and I have the same problem. She was separated from her mother very soon and I have to work very hard on the biting part with her.
I totally agree with mimodok. That is the best tactics.
ALSO I have been trying something new. There was this one time when i realized that i was really nervous when i was telling her not to bite. And it didn't work at all. Then i lowered my voice and told her in a calm way. She immediately let go! :thumb up:
That always works for me. Of course I work with redirection too, but i think that she must learn to obey my words at all times.
She still needs a lot to learn but i think she'll be just fine. AND I recently bought a nice chewing toy for her. That works as a charm!

She doesn't bite as much as she did and she obeys much more.
Try working with that and let us know how it works out!