I think the term hand cannon used by JDJ uses was at the time appropriate. (I have a .430 JDJ in a TC 14" contender.)

But since I now also have several hand gonnes (14th century "cannon on a stick" devices of 90 caliber and BIGGER) the term HAND RIFLE makes much more sense.

If I had to do it again (it was early in the game) I'd do 45-70 over .430 JDJ just because of the lack of need to trim 1/10" of EVERY case.

I think Handgun is a more appropriate term as they are not fired like a rifle and many have barrels much shorter than a rifle with no butt stock. I know there are those that have singleshots with looooong barrels and monstrosities called forends and grips but you will find extremist in everything. What are the 10 inch barreled revolvers called? A pifle?
Why not have the chamber lengthened to the right specs for the 444 Marlin? That is the parent case for the 430 JDJ.