These shotguns are made at the Baikal factory in Russia, and are very solidly made. I believe that all of the barrelsare all fitted in the Russian factory, and not in the U.Ss. They are imported by EAA (European American Arms Co.)
It would probably be alot cheaper for you to just buy a second Bounty Hunter, in the longer barrel version, than trying to buy a spare set and have them fitted by a gunsmith. I know that the Bounty Hunter, and I thinkg Bounty Hunter II, come in longer barrel configurations.
However, about a month ago, I heard that some large gun manufacturer in the U.S. is buying up EAA. Perhaps it was Savage or Thompson Center? I don't know if this has occurred yet or not.
This may have something to do with why the new Bounty Hunter IIs, with true external hammers, are so hard to find right now. Maybe the negotiations have slowed up import or production?
Best Regards,