I just called and talked to the head clerk at the Hilo Firearms Registration office about this issue. She said that there is no way anyone can register a "shotgun", which she says Hawaii defines at "anything that shoots a shotgun shell", that has a barrel length of less than 18". I asked about the ATF definitions of "other firearm", etc. and she said no, Hawaii has "stricter" rules. I tried going in to some detail, but she said dealers here had inquired about selling the commercial models, and that she had called Oahu (not sure who on Oahu, presumably the HPD firearms division) and they told her no, those are shotguns and can't have a barrel length less than 18". She referred me to HRS 134-8 (below, again). I mentioned that someone had posted photos of the specific item she said could not be registered, and that it had been registered on Oahu, and she said "maybe it was an error", or that she didn't know if the posting was real, etc.
Seems I'm in a Catch 22 situation. Any suggestions?
134-8 Ownership, etc., of automatic firearms, silencers, etc., prohibited; penalties. (a) The manufacture, possession, sale, barter, trade, gift, transfer, or acquisition of any of the following is prohibited: assault pistols, except as provided by section 134-4(e); automatic firearms; rifles with barrel lengths less than sixteen inches; shotguns with barrel lengths less than eighteen inches...