gold and silver have historically been at a 9:1 up to 15:1 ratio.  Right now silver is so undervalued it is stupid not to buy it (83:1).  It would be a waste to trade a box of ammo for even a fractional ounce of gold.  Silver is for smaller trades, buy silver bars and keep them for larger trades.  Keep the gold for the really huge trades or for when the world goes back to the metal based currencies.