I have shipped a few heavy and few expensive firearms.
What I have done -- and continue to do -- is pack the rifle in a plastic rifle case, then construct a wooden box from 1x6 pine/whiteboard, etc., and 1/4" plywood. Rip the wood to the case height. Glue and screw the corners together, glue and staple the bottom on, then screw to top on.
As I have a table saw, it is no big deal. If you don’t have one, find someone who does.
A Fellow Shooter once told me that by doing so, I am adding to the cost of shipping and probably another US$20.00+ materials. True, but have you ever had to file a damage claim with UPS, FedEx, etc.? They will “nickel and dime” you, then take their time ‘bout paying. I firmly believe that a more than ample, stout packaging is inexpensive insurance and cheaper in the long run.
