NO,
There are NO LOOPHOLES.
If ANYONE (citizenship doesn't matter) wants to export from the US, any firearms, parts, optics, ammo, or reloading components (including projectiles), it must be done through a registered exporter. A registered exporter has an exemption that they don't have to get an individual export permit if the shipment is under $100. This "exemption" is not an exemption of ITAR, but an exemption that a registered exporter (not an individual, or anyone else) doesn't need to get an individual export license for the shipment.
BTW, the penalties that could be applied for exporting a single projectile are exactly the same for all ITAR controlled items (up to nuclear bombs)....
Typically if a person is caught exporting something like ammo or components, ALL purchases are confiscated and the person is banned from entering the US for a MINIMUM of 5 years (could be up to life). It is exceptionally easy for US Customs to put people on a ban list, a couple seconds, and they don't even need a reason. Maximum penalties are, well, lets just say you don't want to find out.
A ban entering the US also means being on the "No-Fly" list, so you can't even overfly US territory, even if you don't land. Which means to going to the Caribbean would have to be via Europe.....
BTW, it did happen to a CGN member a couple years ago over a questionable item. The item wasn't ITAR controlled, but he was banned anyway by the US Agent, and the member didn't even know until he tried to go to the US a couple weeks later .....
http://pmddtc.state.gov/regulations_laws/itar_official.html
BTW, Canada doesn't really care what you IMPORT, but the US certainly cares what you EXPORT.