I haven't started reloading for my 444 yet but plan to once i finally get everything built and set up.
But there are a number of good bullets that you can use in the 444 Marlin.
Hornady 265 grain
Hornady 300 grain XTP
Swift A-frame 280 and 300 grain
Barnes 225 grain XPB
Nosler 250 grain partition HG
Sierra300 grain sports master
Speer 270 grain Gold dot flat point
And a wide variety from Beartooth Bullets.
http://www.beartoothbullets.com/bulletselect/index.htm
They also have a good article about loading their bullets in the 444 Marlin. Go to the Tech notes link, then scroll down to the link titled
".444 Marlin- Americas most versatile Big-Bore" Parts 1, 2, &3.