It's pretty easy to check in your own area what sells the best by looking at what is stocked the most at your local Walmart and other Big Box stores. I'd have to imagine the top 3 in your Rural Southern areas are still the .30-06, .30-30, and .270. Most all the hunters in my significantly huge family in the Southern states primary goto deer rifles are .30-30 and .30-06. They always tell me "if it aint broke, don't fix it and we been using those for 100 years now". Of course you have your wildcaters like me that was always tinkering with this cartridge or that one just for something to do. I was toying with the 7mm08 years before Remington decided to pick up the round and "claim" it for it's own.

My feelings are that the younger shooter/hunters of today like the idea of "newer" rounds simply because it's "new" technology so they automatically think since it's "new" then it's better. Then you have the brilliant young ones like Mercy that are always tinkering like I did as a lad (still do) because they, as engineers and such, are never satisfied with "good" or "proven over time" and always coming up with fantastic ideas for improvement.

Then of course you have the "magnum" crowds that think whitetail deer have grown kevlar hides and need 10 feet of penetration through solid concrete just to take a scrawny little ole whitetail. Or the folks that can't hunt worth a tinkers damn and have to have 700 yard rifles/cartridge capabilities because they don't have the skills in woodsmanship to get to a reasonable range.