The farthest north I'm familiar with is Wilson-Shoals Wildlife management area.
It's on rt 441 about halfway between Cornelia and Gainesville (approx). Although a little difficult to locate(one small sign heading north from Gainesville) It's one of the best public ranges out in the woods I've ever shot at. About 15 covered firing points with sturdy benches. It's a 100 yd range and best of all it's free. Hope that helps.