As others have said the biggest headache is the over all length. Usually the crimp groove is in the wrong place as most Keith style .44 bullets are designed for the .44 Mag/Spl and not the .444 Marlin. With this is mind and wanting something better that you could actually crimp in a groove there has been many designs that have the correct nose profile and the crimp groove. A guy named RanchDog came up with one design and a few of us got together and designed other bullets from light weight 200gr. and up . If you want cast bullets then you are looking in the wrong place.
www.castboolits.com is the place to look for data.
Myself and a few others have run multiple group buys for various weights for the 444 Marlin and they are all tack drivers. Secret to the older 444's is to size .432 and have the correct length and away you go.
Don't let anyone tell you they can't be made to shoot accurately.
I designed a light weight cast bullet that is hollow point or solid and it works great.
Myself and another member designed this one as a multipurpose bullet with three crimp grooves. Top groove is for .444 Marlin, center is for .44 mag rifle and lower is for .44 mag revolvers. My .444 and .44 mag rifles love this bullet as does my model 629 and redhawk revolvers.
It has taken many animals over the last couple of years.
Just a couple of drawings I did for a light weight .444 bullet. One with tumble lube and one with regular lube groove.
Also look at Ranch Dog's website, he has a few different weights that he offers and they work excellent also. He prefers the Tumble lube for easy lube application so most of his bullets are that style. You can also get his bullet designs in regular Lube grooves from NOE in Utah and he can hollow point them if you want. You can get the correct Tumble Lube sizer .432 on Ranch Dogs site and they work great.
http://www.ranchdogoutdoors.com/
I had a Lyman .432 sizer die made for me from a member on castboolits named Buckshot, don't remember the exact cost but I know it was cheap, 30 bucks plus shipping I think.