Take it to the post office and mail it to the receiving FFL.
There are only a couple hiccups:
1. Will the receiving FFL accept it from a private party. It's perfectly legal, but some FFL's won't.
2. Will the receiving FFL require a copy of your ID (Driver's License) to be included. Most FFL's do, but it's not a requirement of law either.
If it is another Georgia resident that you are selling the rifle to, you can, legally, send the gun directly to the recipient.
http://www.atf.gov/firearms/faq/unlicensed-persons.html#shipping-firearms-usps
Q: May a nonlicensee ship a firearm through the U.S. Postal Service?
A nonlicensee may not transfer a firearm to a non-licensed resident of another State.
A nonlicensee may mail a shotgun or rifle to a resident of his or her own State or to a licensee in any State. The Postal Service recommends that long guns be sent by registered mail and that no marking of any kind which would indicate the nature of the contents be placed on the outside of any parcel containing firearms. Handguns are not mailable. A common or contract carrier must be used to ship a handgun.
[18 U.S.C. 1715, 922(a)(3), 922(a)(5) and 922 (a)(2)(A)]