Re: East-Middle TN shooting
The range is open unless it's reserved. On the calendar you'll see it's reserved for events and practice. On the days other than Monday afternoons that it shows LR Practice, there is usually nobody there so you can go and shoot 300/600, if someone shows up wanting to shoot longer, they can insist but usually they'll just hang till you finish. Monday afternoons is scheduled squadded practice starting at about 4:30PM.
I don't know how much time you have shooting at 1000 yards. It takes at least 2 people (someone has to work the pits) if you don't have your own camera setup otherwise you have no idea where the bullets are going. You can't see hits at 1000. One thing about ORSA, no steel, anywhere other than the action pistol range. On the ranges used for competition (the bullseye range and the HP range) you have to use the correct frames/stands. At some point in history there was at least one BPCR shooter who was allowed to shoot chickens out somewhere between the 600 yard line and the pits but I've never seen anyone in recent yrs.
All that said. To get the combo to the target shed you need to come out and shoot some matches and learn how the range works. I'm not sure of the official protocol, but in practice it's pretty simple, show up and shoot.