HI STEPHEN,
I have used a 44mag Marlin for many years for target shooting, light load,
my advice to you is, use a 44mag case with a 44spl load,
it cuts down on feed problems and has served me well for many years ,
lots of different powders, 240gr head, TC, SWC, RNF,
have a bit play and see what your new toy likes best,
have fun,
T