Have a read
https://help.cbp.gov/app/answers/de...sion/L3RpbWUvMTUxNTIwNjExMS9zaWQvQmRRVVMxQ24=
The reason Briley ships is because they have an export permit. In the case of handguns and rifles it is under ITAR, you can export under a certain value without an export permit. For shotguns it falls under the Bureau of Industry and Security, they have no exception for shotguns, shotgun parts or shotgun ammunition, you need an export permit for all of those. If you choose to do down to the states and buy a choke tube and try to cross the border without an export permit you can get into a lot of crap.
Reloading dies do not fall into these categories, but bullets, wads, powder, primers and brass cannot be exported without an export permit.
Cheers