If YOU ever plan on shipping YOUR barrel, do it right!! Head to your local Wally World and pick up a couple of "pool noodles". $ store has them also.
Maybe $1.50 each. USPS sells a 4"' X 4" box 36" long. Slit the noodle and cover the barrel with a few inches left over on each end. Zip tie about 2" or 3" all along it's length. The end excess will act as a padding so the ends won't get damaged from bouncing around.
Shipped a few barrels to Oregon to get fluted with no problems with them coming back in the same box and padding.
Also shipped a few to NY to "my Man" (

) to get threaded and chamber with NO PROBLEMS.
Came back in the same boxes with no issues. Pack it GOOD and you'll have no issues!!