First off, I live in CT. I'd move, but I've got an awesome career and that is keeping me here.
I thought the HK94 was a rifle? If it's a rifle, and it has a pistol grip and detachable magazine...it's banned as an assault weapon.
The SP5 is banned because it's a pistol where the magazine is not contained in the grip...also as an assault weapon. I also can't have a threaded barrel on a pistol because that would make it an assault weapon. "Pre-ban" stuff is fine, so before the 1994 Clinton AWB unless banned by name...so for example I could have a threaded barrel in an 80's Sig P226 or Beretta 92F...or I can build any kind of AR I want if I find an old PWA lower receiver...but I've really struggled with trying to find any pre-1994 Clinton AWB HK toys.
So, by CT law, a handgun is anything with a barrel shorter than 12". Therefore anything longer than 12" is not a handgun, so it's not a pistol, but it doesn't have a rifle stock and isn't intended to be fired from the shoulder...so it's not a rifle...that makes it an "other" or an "aow"...I believe it's federal law that states over 26" is not an AOW, so no tax stamp...and then I don't know what law the vertical grip comes from, but all the CT FFL's seem to think the vertical grip is required to ensure it's not intended to be shouldered...I'm ok with that if it means I can have a new toy.
It's a very confusing sum of laws and loop holes, but if you google "CT Other" you will find that we found a loop hole allowing us all to buy AR's and just about anything else...the only real rule is the firearm has to have a barrel longer than 12", has to have a vertical fore grip, and cannot have a rifle stock. If it's shorter than 26" (measured with a folding or collapsing brace folded/collapsed) then we have to get an AOW stamp and wait for the form 4. If it's longer than 26", we do not have to get the AOW stamp. Once it fits into that criteria, the barrel can be threaded, can use any muzzle device...anything really.
Only other limit is 10 round magazines. Only exception to that is magazines owned and registered before the law was passed and enacted.
I thought the HK94 was a rifle? Per federal law, once a rifle, always a rifle, cannot be converted to a pistol or other/AOW...so I can have any gun that fits into my above description, provided it starts life as a bare receiver (transfers as other and I can build it into that config myself...easy with an AR...not so much with the HK stuff), or starts life as a pistol, or already built as an other or AOW.
Sorry for the confusion. I guess I should have asked "what configurations of the MP5 style gu nhave a barrel longer than 12" but aren't rifles?"