Our range out near Enid has steel targets set up out to 500 yards. It is lots of fun. I haven't tried it since my eye surgery but hope to do better with the new peepers. I use iron sights so I'm not sure what to expect.That's exactly what I do.
I haven't read the whole thread to know if someone mentioned this, but you might attend some of the long range matches in western OKlahoma to get a feel for how it's done. (i.e. equipment) Also what is possible, there are a lot of shooters in OKlahoma that can reach well beyond 500 yards with precision.
Michael