From today’s letter to Survivalblog concerning caches…
A reader dug his up to inspect the conditions and commented on how well the Russian spam cans held up. The pictures tell the tale. 
The author indicated that he buried the spam cans in 2009. That gave them five years underground. They’re not looking too good. For that reason I felt it pretty prudent to post this, since I know many in the audience at a minimum has some ammo cached somewhere (among other essential items…right???) and the experience needs to be shared.
I’m not picking on you (seriously), but this is not how you cache anything. Spam cans are great for shipping ammo and keeping it all in one place for a long period of time, but when exposed to water some problems pop up. Metal does what when exposed to water…rusts…right? Dirt does what over time…holds water right? Right? So while the green paint does a bit to mitigate the rust, it’s not going to stop it. In five years’ time he has a spam can that now is dangerous, because while it may not appear to be punctured, water still may have gotten in, which may have damaged your primers. Hopefully it didn’t.
Anytime you stick any metal in the ground, at a minimum wrap it in a plastic contractor’s trash bag (they’re very thick and generally much stronger than household bags) or spray it down with POR-15 (an extreme anti-rust primer…expensive but worth it) before sticking it in the plastic. If at all possible, take it out of the spam cans and put it in something more creative that doesn’t scream,”I’M AMMO!!!!”, along with a few other useful items that you’ll need if you’re digging up ammo (like the weapons themselves, maybe some kit and magazines to carry the ammo, maybe some spare tools, maybe some antenna kits…just a thought) Attached is the Army Special Forces Cache Guide for you to download. Read it over.
special-forces-caching-techniques-tc-3129a