Take exit 320 off I-75 and head WEST on Resaca Lafayette Rd/Route 136. After a few miles you'll reach the end and you'll be forced to turn either right or left. Turn RIGHT (I think it's still called Resaca Lafayette Rd/136) and go about 1000 feet and on your right side you will see a dirt road with a sign for Chestnut Mountain Rd. Take the dirt road and you'll end at the shooting range. $5 admission (in an envelope). Be honest. If not, the park rangers may check the payment box and see your car's license plate didn't pay. Then you will be in a world of pain.
While we are on the subject... are there any outdoor ranges close to Vinings/Smyrna/Marietta? Driving to Chesnut Mt., Adairsville, and Creekside ranges are at least an hour away. I'm willing to pay for a membership if the drive is half an hour or less.