[paratrooper]

Wouldn't a light coat of cosmoline help with the weapons ? If you don't "GUNK" it on you can wipe it pretty clean in no time . If you put stuff in pretty big containers you could rig up a vacuum pump to evacuate the oxygen . Put a gauge on it so as to know when to pump a bit more now and then . Water boils at -90 degrees at 0 atm. . Unless you need access at the speed of combat there are a few good ways to preserve .
Not to be nosy but what caliber are you gonna be "heavy" in ? .223 and 7.62 will always be around and in HUGE supply . The M-16 will be the weapon of choice for the Gubmint as will the M-60 . These calibers may become guarded but surely not extinct . Good luck .