Bob McBride
54 Cal.
Caps can be sent UPS with the proper markings on the package.
I believe you also have to ship from the Customer Service office at a hub. That is true of shipping BP firearms via UPS. They only ship firearms and hazmat via ground. On another related subject, a nice piece of advice I got from a worker at a hub that was a BP shooter was that if you take the pistol apart (read: in two pieces) it can be shipped via air as ‘black powder pistol parts.