I am trying to decide which cal would be better for me, both for survival/hunting and in a SHTF situation (I can only afford one or the other). My understanding is that a 5.56 rifle can fit a (very slightly) smaller .223 shell, but a 5.56 shell may be tight in a .223 rifle, not to mention the possibility of problems dealing with the higher pressure 5.56 round in general. So it would seem a 5.56 would be the better choice from a flexibility standpoint. But here is where it gets a little blurry.... I see *tons* of .223 ammo for sale, but very little 5.56. So if .223 is more readily available (and cheaper?), why not just get a .223 anyway? I can also get a S&W M&P 15 or a Mini 14 for hundreds less than a quality AR 15. So it would seem a .223 would be the better choice from a cost standpoint. What do you guys think?