[Old and Reliable]

You don't need to be either a "Plummer" aka- Christopher, or a "Plumber" which comes not from Plumb, Level and in Square- but from Pb or Plumbe- the Latin word for lead- as were the original feed and possibly drain pipes for older houses- we all know Lead is a "No-No' for paint, and unfortunately, also for hunting dem ol' webfeets-

Pipe schedule is a numerical scale, just as are the gauges of our beloved shotty-guns-, but in reverse- Schedule 80 has a greater wall thickness than Schedule 40-- 20 is a higher number than 12, but we all know which number represents the larger bore dia. in a scattergun-

I use nothing but PVC schedule 80 pipe with appropriate sized caps for shipping barrels, or any other tubular object and wrap the item(s) with bubble wrap, and pad both ends. Lowe's, Home Depot or any quality builder's suppy outfit should have schedule 80 PVC- or they can get it for you- usually comes in 10 ft. lengths- according to my ASTM sheet, Code D-1785- a 3" I.D. schedule 40 PVC pipe will have a nom. wall thickness of 1/4"- so the O.D. is then 3 & 1/2"- and then the Cap I.D. would be the same- BUT schedule 80 has a nom. wall thickness of 3/8" so the O.D. is then 3 & 3/4"- I can also check the crush strength ratings in PSI for both 40 and 80 if you'd like-

Calvin- you were lucky that the barrels weren't damaged- under normal conditions your packaging process would have been A-OK- but with the "Fragile" tag- sorta like a red flag in front of a angry bull-