the answer to your question lies in what actually happens as things deteriorate. if we have a road warrior type situation where everything falls apart and people are killing each other for food, i don't know how far gold will get you. there will be "warlords" in that situation who for one reason or another may "sell" you stuff(food, guns, your life) for gold only because they can afford to do so. after all, gold has more than just a monetary value. humans, it seems, are drawn to it. has something to do with it's vibrational quality. of course, in that situation, it might just get you killed.
in a Depression situation, it might be able to buy you some food from a farmer or hoarder. i would think it would be worth about the same as ammunition or alcohol. in other words, just a bit more than food/water.
in the early part of this century, a quarter ounce of gold was worth a days pay(if memory serves correct, which it does not do much these days). a days pay equaled X amount of hay, or corn, etc. actual silver money(90% US silver coins from before 1965 for example aka "junk silver") might become a unit of exchange again if things go bust. nobody is going to be taking paper money or steel or zinc coins after a major crash.
when the money is worthless, those who put their money into gold and have managed to hold onto it will have something after things stabilize whereas those who kept it in the bank will have nothing.
right now there is huge manipulation in the gold/precious metals market. the price of gold is based on the price of paper gold futures. a commodity that is easily tinkered with. by shorting the sales of these futures, the central banks(powers that be, the players, etc.) have now put themselves in the position of lowering the paper price below that of a "demand" price.
it now costs more to "produce" an ounce of gold than it is worth due to cost increases of everthing. because of this, government mints around the world have stopped minting gold. they are forbidden to buy gold above a certain spot price. when the cost of producing gold is higher than spot, they can't buy it. so they just have shut down production and are waiting for the spot price to go up or the production price to go down.
this very basic situation violates all rules of supply and demand. it goes against logic. so, buy gold if you can. not because it's gonna buy you some food, but because it will be one of the few things that will hold it's value when TSHTF.
ps, 5 ounces of gold will weigh a heck of alot less than a hundred rounds of .223 ammo.