A lot depends upon WHICH powder & primer combo you use.
I load .44 Spl in .44 Spl cases using a tried & proven load of 7.5 grns of Unique. But if I wanted to load that same load in a .44 Mag case,, I'd measure things to make sure there was not an excessive amount of air space between the base of the bullet and the top of the powder. There will be an air space in the .44 Spl case,, and it should only increase by the same amount as the different dimensions of the cases.
But if you wish to be safe,, you can do what many used to do long ago,, (myself included,) when using a very hot fast powder,, (Bullseye,) in .38 spl cases. #.2 grns of powder & a WC bullet. To assure correct ignition, and uniformity I would place a "space filler" of a small wad of poly fiber fill material (normally used as pillow stuffing,) on top of the powder, below the bullet. It would occupy the empty air space, and allow uniform ignition.