Ok, sorry I was away for a while, but I'm back now to answer the questions concerning my build-up.
Firstly, to clarify, the 5.56 is a hot NATO round of the .223 Remington. I agree that the .308 is superior in every way, as is the 6mm. A .308 at 1,000 yards is like being shot point-blank to the chest with a .357 magnum - at 1,000 yards!!! (or meters, whichever you prefer).
Why am I choosing .223 here? Part of it is the economics here in the states. .223 is cheaper, as well as being much more available in large bulk quantities. Also, while I shoot for accuracy and distance, I'm not shooting out to 1,000 yards, so a .308 is just overkill the whole way around. While a .308 will punch through a tree with ease, a .223 with hit, fragment into several pieces, tumble around inside, and generally make one helluva mess out a zombie and/or alien if shot in the chest. If shot in the head, well - doesn't matter, does it? Dead is DEAD.
I don't even have an AR based platform, I am going to use a bolt-action Savage stainless target action mated to an XLR Industries stock, AI Magazine, and a nice Mil-Tec scope of some sort. I want to be able to legally hunt with this rifle as well (if I had the desire too) so I have several uses in mind for my build-up besides just killing zombies or some soon-to-be unmasked Reptilian Anti-Christ. My maximum desired distance would be 500 yards, with a .223 will do with ease. I just bought 200 rounds of Fiocchi .223 V-Max cartridges. :-)
My daily carry is a Diamondback .380 due to it's incredible concealability, great sights, and ease of cleaning. It's basically a slim, mini-Glock with better grip angle and ergonomics. Just a great pocket pistol. :)
Thanks for all the great responses guys, it's been a fun read (and different) here on JWD.
- Wing Commander