Yep, what he ^ said. Butner is THE place for long-range shooting in the eastern U.S..
I'm a member of the club there (NSSC). You don't have to be a member at all to shoot - just show up at a match with whatever you bring and we'll assign you a relay somewhere. Check the schedule on our website for upcoming matches and directions. Just show up at the pits the morning of a match (before firing has begun, obviously) and introduce yourself to the first person you see. If you would like to meet me, just look for the good-looking guy with all the shooting-groupie chicks hanging on my arms. ;-)