Regarding my Barrett M95, I want to put it away in my safe for quite some time: is there any procedure I should undertake to ensure that it doesn't become damaged? It has never been shot or cleaned, if that makes a difference.
I'd recommend cleaning it thoroughly, giving everything a light coat of effective oil (I highly recommend Ballistol), and securing it carefully inside the gunsafe, which I assume is in a cool, dry place.
I agree with AK. You might be interested to know that almost 20 years ago, I stored 27 rifles in two crates. I went to school in another city and i had to store my guns.
Anyway, I sprayed them down with SuperLube, which is a special synthetic grease that contains teflon. This product comes in an aerosol can and it sprays like an oil. But then it hardens into a very slick grease.
After 4 years my guns were still in perfect order. I did not have the slightest hint of rust.
Assuming you do the cleaning and basic lubrication that is called for, you need to include some kind of desicant or humidity eating device or compound in your storage room or on the rifle itself.
My father in law stored his NRA pistol equipment in his Houston garage in the late 1950s and recently looked at is again - it was perfect. Lesson learned in a big way. Vapor phase Inhibitor or what is now called VCI paper or crystals. I forget who makes a rifle storage bag that includes the VCI compound inside the bag. VCI is your key to happiness.