To me it seems the .308 is a logical progression from .223. Kind of like when you buy your first dirt bike in 125cc and soon discover you need more power and upgrade to a 250cc. The problem with that analogy is that after a year or two you upgrade again to a 400-500cc (.50 cal?). ;D The ammo is abundantly available. The local Walmarts around here are sold out of just about everything, but they had .308.