I would go .308 for for availability of parts, ammo, reloading components, etc. It is readily available for a decent price (which will allow and encourage you to shoot more and store more). Especially when you consider S & P, many other folks will have .308 guns but I doubt many, if any, will have 6.5CM guns. Choosing 6.5CM for a survival situation would severely limit your ammo scrounging potential