I made a 4-bore muzzleloader in-line rifle made in Johhanesburg,SA..Well the problem is the airline won’t ship it..I also didn’t the custom import paperwork..To find I don’t need it..They call is a dangerous item..Can someone help me?

If it is not loaded how can it be a "dangerous item"???

Oh wait, I know... it might club someone in the baggage compartment.

You may be in a pickle. 4 bores are not considered sporting arms by the ATF and they will deny applications for importing them. It may be a muzzleloader but because it is inline it is considered a modern arm. In summary, I do not think you can import that gun. It would be best to contact the imports branch directly and ask to speak to a specialist, (304) 616-4550.
Steve