I just sold a rifle of Gb a little while ago. Pack it up well with bubble wrap and cardboard. If shipping USPS, enclose a copy of the dealers FFL and bill of sale. Write the address on the box with permanent marker because labels get lost in transit sometimes. Keep a second copy of the documents with you when you go to the post office. Declare that you are shipping a rifle and the clerk should ask if you have broken it down and unloaded it. They may check. They will also keep a copy of the FFL and double check the shipping address against the bill of sale. Send it priority mail, insured, adult signature required. It should take about $30-40 to ship that way. If you get paid in USPS MO you can pay shipping and cash your MO in one shot. Handguns have to go 2nd day Air UPS at a shipping hub, similar process.