I've shot hundreds of plated bullets through my 4 inch .44 magnum, the Lee factory crimp die works well for crimping plated bullets, since it creates it's own cannelure. If done correctly, you won't cut the plating. Definitely worth a look.
I'd go with 240 grain bullets in a 4 inch, just to keep velocities up and recoil down. Full power reloads can reach close to 1300 fps from a 4 inch. The recoil from these is very stout! I can only imagine what a full power 300 grain load feels like.
FMJ won't expand and isn't intended for hunting. You want a quality SP bullet for game.