Quoted:
I don't know what your version of SHTF is, but mine does NOT include electricity to keep meat edible. So for me, I will have to make sure that what I kill I can eat that day. Other, bigger predators will smell the left over remains of a deer and will invite themselves over for dinner. I see far more rabbits, squirrels, snakes, and other small game animals than I do deer and antelope. 30-30 wouldn't leave anything left of the small game. If a deer presents it' self, a 223 will take it down, just can't take a 500 yard shot on it. If you can carry both, then go for it, but if I have to pick between the 2 I'm going with the 223. Plus, you can carry twice as much 223 than the 30-30. (based on the weight of the cartridge.)
A problem even bigger than food storage would loom large in a SHTF event widespread enough that you would find yourself hunting and foraging for food. Game populations will drop so fast finding anything on four legs, or with wings, to shoot will get hard fast. Game populations took 30 years to recover in Iowa after prosperity returned following WW2. My grandfather was old enough to grow up hunting out of necessity and the mindset people from his generation possessed is amazing to consider.
223 will blow to shit any small game you tag with it. In the midwest I would have no problem hunting deer(small game, foraging) with only a .22 considering head shots out to 50 yards are easy and I can't remember the last time I needed to take a 50 yard shot. Out in open territory its a whole different game.
I'm not taking issue with your post. I just wanted to share my opinion that if we "need" to hunt for more than a few weeks our caliber choice will be the last of our worries. I vote for either caliber.