All regulations can be found on USPS website. I recently shipped a shotgun out of state. If you're shipping within the same state to a person legally allowed to own, you can ship a long gun directly to their house. ALL handguns must be shipped to an FFL holder. If shipping a long gun out of state, must also go to FFL holder, or to yourself at your own residence in that state. You are required by law to declare to the post office that it is a firearm you're shipping. They can demand you open for inspection to insure not loaded. They are barred by federal law from indicating on the package that is is a firearm after it is declared. Insurance/signature on delivery and all that is NOT required, but I recommend it. They may also require you to either verbally or written, certify that it is unloaded and not being shipped with ammunition. The post office counter worker might argue with you on the legality, they did with me. I made them look up the law, after an hour wait I got an apology from the post master and the inspector. You just need to be assertive with them. You know gov employees don't always know the laws they enforce.