The reason the Ponca City range requires NRA membership is because the NRA insurance is the only insurance the range can afford.I would try joining a club in a heartbeat but every one I'm aware of requires NRA membership which I've sworn off
In response to some members that had became disgruntled with the NRA I went to a couple of independent insurance agents to see who would insure the range and at what cost.
Only one insurance company offered to insure the range but the cost would be over $100,000 a year.
I suspect the same situation exists with the other gun clubs you mentioned.