We started playing around with this eventuality in the 1990s. A few observations:
We buried old guns and cartridges in 155mm howitzer tubes (M82) in our garden, where they were regularly watered over. End-result ? With dessicant tins inside, they were A-OK after 6 months. Others buried out in the boonies, without regular water-challenge, were A-OK after 12 and 18 months. No rust. Cartridges went bang. Guns functioned flawlessly. We’d prepped them with ProLix, a non-petroleum based cleaner/lube/protectant. ( ProChemCo, ph. 800-248-LUBE ) I’ve tried most products and this is superior. I’ve cleaned scrupulously (can you say “OCD”? ) with others on successive days, waited 24 hours, and pulled more residue with this stuff. Excellent product and a good crew at their new location. I cache weapons in a “ready-to-go” format, with basic ammo load, BoreSnake, a 1-oz Prolix, special parts (as indicated), and a few other goodies in a fanny with the weapon. As example, broken-shell extractors, extra mags or stripper clips, a Fobus [holster], extractors or other parts likely to fail are squirreled away with the gun. A good folder, lighter, compass, and other elective gear are easy to pre-pack. I’m lazy, and fallible under stress, and try to simplify and streamline the protocol for Grab ‘n Go!, predicated on prior setup in a safe container or secure locale.
A quick note, the various “burial tubes” should not be emplaced vertically; it’s virtually impossible to remove them quickly if you do so. Pick a spot with nearby metal, or salt the area with scrap rusted metal. In this neighborhood there are utility boxes, poles, and fence lines to shadow any detectors and function as markers for us and others. Lay them in, with a rope affixed to one end, and they pull out readily. Seeding in more junk metal to an area with doubled radius increases the search area by a factor of 4+. Eventually the job becomes too difficult – in any real sense – for the searchers.
The 155mm tubes were available from an Illinois company (Shotgun News may still have them as a regular advertiser) and they easily function as a full blown survival capsule. The ends have seals, and can be tightened with a 2 x 4 section. Prep the O-ring seal with Nu-Vinyl, and have a small tube of silicon grease sealant , and when needed, they can be readied and dropped in place.
The 25mm cannon shell boxes used to be a real bargain, but their days at $5 are long gone. They are as durable and effective as the tubes, if you are willing to pay the price that they command nowadays. Look around your property and neighborhood, and the best spots will eventually jump-out at you. – MurrDoc