Be mindful the airport staff are 10 times worse than postal staff when they here any mention of the words "gun, rifle, bullets, etc". Depending upon the agent on duty, panic has been seen to occur at the mere mention of a gun. Our German friends take barrels and rifles back and forth with them all the time, but all must be checked now. If it were me I would remove the breech plug and put it in my suitcase, then all your are carrying is a piece of 12L14 water pipe tubing. You might could carry it on that way, barring any size restrictions of course.