We line crates with Daubert brand VCI paper for shipping printing presses overseas.
Unless you buy a large (and very expensive) roll, you're going to be stuck going through distributors like U-Line.
Here's a win-win combination....
wipe surfaces with preservative grease (or believe it or not... WD-40 works very well)
wrap in VCI paper
place in a vapor barrier bag, evacuate air and zip/seal)
put the bagged gun in a box, to protect the bag.
Good to go.