James,
I can't imagine rust is the issue in Arizona that it is is some other parts of the world.
That said, getting back to the original question, I suspect trying to vacuum seal guns could actually be a disaster, if the vacuum got near the threshold of 22 inches or so. Any moisture left in the wood would begin to boil off around 20 inches, and I don't believe this would be a good thing. It would likely result in splits, cracks and shrinkage over time.
I doubt a home food preservation system can get down to that level of vacuum, but, it might just be a case of the same thing happening but, not quite as much of it at once.
The best way to counter rust is to find a way to keep the metal in the guns at the same temperature and the same hunidity (40-50) at all times. If the metal is cool and is suddenly put in warmer, more humid air, you will get condensation, and it will begin under the oil you have put on the gun, rendering it useless.
If you can't control the temp and humidity, you will have a hard time controlling rust.
Best,
Ted
