Check out Accuracy Systems: http://www.ruger-mini-14-firearms.com/index.phpthey do a bunch of different calibers for the AR-15.

If you just want an auto for hunting, I would check out the Benelli R1, I just bought one for my Dad and it shoots awesome!! It is a .270 WSM and if doesn't kick one bit. That rifle is definately my next firearm purchase.