Do you have to declare that you are shipping barrels when you ship them? If they aren't an entire gun, I would ship them as sump pump pipe or something. You also might be able to go to your local gun dealer and see if he doesn't have a box lined with styrofoam that guns originally came in. I have gotten them from my stores/dealers before. Or if you have purchased a gun you might be able to use the box from another gun. Then I would insure them as someone else mentioned. Good luck.