If you are into the carbine rifle thing, try a Kel-tec SU-16. The thing weighs about 5 pounds, has a fold out bi-pod, can take AR mags, has a build in rail, more accurate than a mini-14, and all for around 4-5 hundred.
Thing is, the thing is almost entirely made of polymer.
Here is a review:
http://www.ktrange.com/articles/a6/a6.html