John,
I just recieved a shotgun from Canada at LAX this year. Yes, you have to clear customs. Likely, with a gun made outside the U.S., you'll have to pay duty (not sure on that).
It will have to be imported either on a Form 6 by a FFL or a FFL with an import license. Mine came to the air freight company and I went down and signed for the paperwork and took the paperwork to customs acting as an agent (with a letter stating so) for the recieving FFL. Customs reviewed and stamped the paperwork, charged a small fee (my gun was a Browning Super which I represented as having originated in the U.S.) and I took the Customs approved paperwork back to the air freight reciever and they handed it to me to deliver to the FFL for my DROS and waiting period.
You may want to get ahold of Ted Schefelbein on this bbs as he is licensed to import as I recall.
