nice score on the indexer.
I have talked to guys who have made the 444 marlin rimless they used a standard 444 marlin reamer an then used a chucking reamer to remove the taper to work as a stop. most reamers ahve extra neck length to you will have to runthe reamer short or make our brass longer.
the 444???? will need a special reamer or need to be cut with a boring bar.
I think you can use 444 marlin dies however. i have made brass for it. you will need to likely inside ream it. it would be best to expand it straight with a arbor an then sixe it in the dies an then ream the neck area to a correct id.
when this thread was started there were no leverlution bullets avalaible so you were stuck with pistol bullets. The bullet length dictates the case length if you want to get as much capacity as possable. today thre are leverltution bullets avaliable IMIO they wlould be the best for feeding with there plastic tip as well as for veleocity etc.
If i were to retake up work on this project I would start witht he heavest 44 leverlution bullet an work back ward setting case length the allow the bullet to be seated at proper depth at a near mag length OAL loaded length. id make the reamer form the loaded round.
I have been thinking about this round a little more the last few months.Its occured to me that more caxe taper would benifit the it creatly for feeding an also to make it work in a some sort of standard round. I have been working on a 6.5x55 swede an it has a bigger case head. If 6.5 swede brass were used ( yea the cost goes up to make it) then you could have more taper in the round. american swede brass is a little undersized . european brass is closer to the claimed .080 case head it should have. At any rate it would give you a round with more taper. food for thought.