Another thing to consider that has only been touched on briefly – WEIGHT. Carrying a larger-caliber rifle means a lot more weight and bulk to lug around, something to consider carefully in a survival situation. There is also the weight of the ammo – a box of .22 LR weighs little and gives you 50 opportunities to hit something, as compared to 20 for a box of .223-caliber that weighs about the same. Non-marksman that I am, I’d opt for the law of averages.