RE: pack them correctly, with several layers of pvc pipe as the canister. ====
How exactly is this done? Wrap in a oil soaked rag, then perhaps garbage bag, the silicone seal the 4 or 6 inch PVC pipes that have end caps?
Found some good advice.
BURY YOUR GUNS?
Lather them with gun packing grease cosmoline rust preventive. Axle or high temperature bearing grease could work too. When you take them out, one can clean off with an alcohol or acetone base liquid like gasoline or thinner. Next wrap the guns in wax butcher paper before placing them in the pipe. Do NOT use plastic....Plastic sweats meaning condensates, which leads to rust.
Put them in an eight or 10-inch PVC pipe. One can cut pieces to accommodate long guns or handguns. A couple of caps or a threaded plug can be used on either side and you can tighten these up further by sealing any gaps with silicone caulk. https://www.guns.com/news/2015/02/21/bury-your-guns
What about your ammo?
Buy mil-spec factory ammo—you’ll know it’s sealed by the red dye around the primer. Cold temperatures are horrible on ammo—it messes up the powder inside the casing and will result in low-pressures. To avoid this, you’ll need to go below the frost line when you dig your hole. Depending on what part of the country that is, about four feet should suffice (no worries, metal detectors won’t usually detect down that far). Also, don’t forget extra magazines and little lube (not grease) to keep them nice. Again, don’t wrap anything in plastic.
Chances are, if the ammunition has been made in the last century, and has been stored reasonably well, then it’ll still be good. If you come across a box (or can or pallet) of ammo made after WWII, and the exterior doesn’t show signs of obvious damage or corrosion, it should be fine. For storage, the biggest thing is to keep it from resting in water. Keep it in some kind of waterproof container. Double-bagging, using a vacuum sealer, and related strategies should all work fine. Avoid freezing, as this can cause some gunpowders to “crack” – to make smaller particles. While it may not seem to be a big deal, it can greatly increase the surface area of each small particle of the propellent. Which can cause it to burn faster. Which can cause over-pressure. (https://www.guns.com/news/2011/08/17/storing-ammo-long-term-because-without-rounds-your-gun-is-just-a-poorly-designed-club)