When shipping for service, contact the service entity first as they have a list of things that need to be addressed such as UNLOADED, removal of scope or any other non-stock/unneeded items, moderator, magazine and the like.
They will also suggest a maximum air charge bar if shipping a PCP for instance.
They normally want the barrel removed as well, at least FX does, and if you have a factory hard case, that is best. Just box up the rifle in the hard case with the factory foam, then put the hard case in a cardboard box for shipping.
It's also smart to include your contact information in the hard case along with the repairs needed.