Unless your state or local ordinance otherwise precludes your rights under the Second amendment;
'Antique' firearms need not be shipped to a licensed dealer. These can be shipped directly to the buyer. An antique firearm is a firearm built in or before 1898, or a replica thereof. The exact ATF definition of an antique firearm is:
Antique firearm. (a) Any firearm (including any firearm with a matchlock, flintlock, percussion cap, or similar type of ignition system) manufactured in or before 1898; and (b) any replica of any firearm described in paragraph (a) of this definition if such replica (1) is not designed or redesigned for using rimfire or conventional centerfire fixed ammunition, or (2) uses rimfire or conventional centerfire fixed ammunition which is no longer manufactured in the United States and which is not readily available in the ordinary channels of commercial trade.
Also if you are shipping a cap and ball revolver, It is suggested the you disassemble it before shipping. That way if they X-ray it, it will not look
like modern gun. This is what the post master here told.
I only place two stipulations on a customer that might seem to infringe on the freedom guaranteed in the Second Amendment. One, I advise that responsibility for complying with any federal, state, or local laws that might have bearing on the customer's ability to own or receive a muzzleloader, is solely the customer's. There are too many conflicting ordinances in different parts of the country to keep up with, so it's up to the customer to stay in compliance. In cases where I do know there is a legal issue, I won't knowingly break the law.
The other is that I require a photocopy of a driver's license or other legal ID proving the recipient of one of my guns is over 18. If an adult feels this is intrusive or unfair in some sense, too bad. There are households where the parent or parents might not want their children to own or possess even a muzzleloader, and I think most responsible parents would at the very least like to be aware their kid is involved in a transaction to buy one. If someone's over 18 I feel whatever conflict they might have with a parent is between adults, at least in a legal sense. If they're under 18, even if there are no legal issues involved it's a matter of courtesy to the parents to require that they be involved in what's going on.
I certainly don't agree with the idea that kids as a general rule shouldn't be allowed to have guns, but if I expect my views, feelings, and actions to be respected I'm obliged to extend the same courtesy to someone whose feelings on the matter of gun ownership differ from mine.
Otherwise I feel the buying, selling, shipping, and receiving of guns in general, not just muzzleloaders, between law-abiding adults, ought to be subject to exactly zero restrictions, and that so far as muzzleloaders go if the feds permit their transfer without restriction that ought to be the last word on the subject.