Another fan of the Ar-7. How nice to meet you. This would be my first choice in a survival situation, most likely used as a single shot, although I do have extra magazines.

My centerfire rifle is a relatively lightweight carbine (Rem 600) in 6mm Rem caliber - a fairly obscure cartridge very similar to the 243. That situation doesn't bother me - I handload.

I would advocate that practice for anyone serious about using their firearm in adverse circumstances. It isn't that hard; our grandparents handloaded around a campfire, at least when melting lead for bullets. Simple hand tools are all you really need. I find handloading almost as much fun as shooting.