What do you consider “long-term? If it’s anything over a year and you expect to store the guns in a damp climate, you will have to protect them from more than just ordinary conditions. Way back in 1999, when everybody was worrying about Y2K I conducted an experiment in gun storage.
First, I bought a four-foot long piece of 6” dia. ABS pipe. I know, most people think PVC is best, but I’ve seen too many pieces of PVC that have cracked when hit or bent over a piece of rock. ABS is much more flexible and resistant to such problems. I also bought two caps for the pipe. I didn’t buy a screw-on type cap since I was experimenting with truly long-term storage. A screw-on cap would be fine if you were planning to take the gun out and use it occasionally but counterproductive if otherwise.
Next, I bought some oxygen absorbing packets. These are pretty common in some areas of food preservation like bags of beef jerky and can be bought from a variety of sources in a variety of sizes. I cleaned and oiled the gun just as if I were putting it in the safe until next week. I then determined just how much oxygen I was going to have to absorb. The inside diameter of the pipe divided by two and squared, then multiplied by pi and the length gave me the volume of air. Since normal air is comprised of only about 16% oxygen: (6”/2)2 x 3.14 X 48” x 0.16 = 12.2 cubic inches O2
This is no time to be nit-picky, toss in a little extra O2 absorbent, just don’t let the packets come in contact with the steel of your gun. Some plastic film cans with holes cut in them work well here. Glue the caps on both ends of the pipe and bury it or whatever tilts your windmill. Within a couple of days nearly all the available oxygen is trapped in those packets and no longer available to form rust on your precious gun. I left mine, a Chinese SKS and some ammo, in the tube for a full year in a wet climate before I checked it. I had marked the outside of the tube so I’d know where to cut without harming the gun. When I started sawing I was a bit apprehensive. The SKS was a cheap gun but I still wasn’t interested in trashing it or finding it covered in rust. But when I broke through the inner wall of the pipe I was rewarded with a “hiss” as air was sucked into the pipe and when I finally took the gun out it had no rust anywhere and was perfectly serviceable, which fact was proven by firing off a clip of the ammo I had stored with it.
Now, I realize my experiment only lasted a year and I’m extrapolating that it will work for longer periods of time. But since rust is oxidized iron and the oxygen is removed from the enclosed atmosphere and since I found no rust anywhere on the gun, I believe it is a safe assumption to make. – D.Y.