MTM Case-Guard has developed a ammunition storage can designed specially for burying in the ground.

The Survivor Ammo can was designed to secure important essentials that may be needed in the future.  The Survivor Ammo Can will hide important documents, gear and even emergency food underground.  The capsule is completely waterproof/weatherproof with the double O-ring seal and uniquely designed protective cap.  The protective cap serves dual purposes as it drains water away from the seals with its overlay design, it withstands the additional weight of earth and acts as a vacuum seal that keeps dirt out of the secure screws in the can and endures the possible impact from a shovel with extracting the unit.  The bucket-style design of the Survivor Ammo Can will house up to 600 rounds of .45 ACP or 500 rounds plus a handgun.  Sometimes the safest place to store things is right underfoot.

It will retail for $29.95. Your only problem will be trying to find (or afford) enough ammo to fill up!