what gun specifically are you talking about?
shorter guns like pistols might be pretty hard to get shooting over 366. longer guns where expanding liquid gas has more barrel to build pressure have a better chance, but if your gun builder doesn't have access to greengas/propane it might be a bit tricky to figure out what it will shoot with greengas/propane vs duster, and more difficult to import because without that paperwork to prove that it shoots over 366, it could be seized/sent for testing/you may never see it again.
This might also be a topic better discussed in the AVed section if you're talking to an overseas store modifying a <366fps gun for importation into the country.
I futz with V2s, V3s and V6s. I could be wrong... but probably, most likely not, as far as I know.
Last edited by lurkingknight; April 13th, 2014 at 00:56..