There's a free, public DOW range on US40, between Hot Sulphur Springs and Parschall. A long drive, but a nice one, and there's some pretty long rifle ranges there. Pistol, shotgun and bow ranges too. There's this sign there, but I don't have the stamp and have never seen anybody asking for them.
You could also join up at Ben Lomond Gun Club, we have a high-powered rifle range out to 600 yards. www.blgc.org