A cane gun is regulated as an AOW or "Any Other Weapon" in the NFA.

You will have to complete a form 1, get CLEO signature (or go trust/LLC) and wait for the tax stamp before manufacturing the cane gun.

AOWs are cheaper to transfer between owners... only $5.00 instead of $200.00. Unfortunately, MANUFACTURE of an AOW is still the normal $200.00.