Load Older Messages from Google Groups Feed

Is there any way to load older messages from a Google Groups forum, let's say sf and friends?

There are RSS and Atom feeds, but I can only access the most recent 50 messages with them.

I'm asking this because I need to write a script to scrap all messages in a (private) Google Groups forum. So if there is any other way of doing what I need, it will be appreciated also.

Thanks!