Try
http://hodgdon.com and
http://powerbeltbullets.comthey have tables that will answer your questions
I find that using 2 X 50 grains triple Seven pellets with 295 Powerbelts will give you approximately the same impact point at 50 yards as 245 grain Powerbelts and 80 grains (1X30 plus 1X50 pellet) in my 50 cal
I prefer the heavier bullets for deer while the 245 for coyote..The charts show little difference in impact point between the 245 and 223 at 100 yards
If you just want to practice any bullet with 80 grains of Triple Seven pellets will usually suffice as shot groups are what you are looking for and not point of impact. You still will have to zero with the hunting load you will be using.
Loose powder will be less expensive and more versatile but I find the pellets make it simpler for a new ML shooter.
You will have to fiddle with different bullets weights and loads to find what your rifle likes.
Develop a rhythm in your loading sequence until it becomes automatic which will help if you need a second shot for the other deer