Ohiochuck,
Here is a link to an ATF page

https://www.atf.gov/firearms/qa/do-i-nee...-specifications

It states the you do not need to file an ATF form 6.
Not at all sure about any Customs and Border Protection regs.

Best to check with both before proceeding.
You may also want to consider contacting someone who imports on a regular basis.
Let us know how this works out.
Mike, also in Ohio