This is is from a site regarding National Forest usage:
Also from another site regarding general use of firearms in National Forests:
Firing a gun is not allowed: (1) in or within 150 yards of a residence, building, campsite, developed recreation site, or occupied area; (2) across or on a road or body of water; or (3) in any circumstance whereby any person may be injured or property damaged.
Now, having said that, I think the situation in GA may be a little different and I have not yet confirmed this, as it's an avenue I've just started looking down. From what I've been told and also from what appears on some maps, the Forest Service has some sort of agreement with the state of GA to allow them to locate WMA's on National Forest Property. Because the WMA's have their obnoxious little subset rules, this can change the allowed usage of the land. The best thing to do would be to write a letter to the US Buereau of National Forests and try to get something back in writing.
Yeah, I know, good luck, right? That's probably why I haven't done it yet. Just about nothing short of a letter in GA would make me feel kosher about plinking in a National Forest. In other states, that is NOT the case, especially out West when you get into BLM land.