I would leave the Powerbelts as my last choice, 250 gr. Shockwaves, Hornady's, Barnes expanders will all give you much better terminal performance.
I am partial to the Barnes expanders, only because I have a long proven personal track record of excellent performance. I like a solid copper bullet in the event of a high shoulder bone hit. I don't have to worry about separation of the jacket and the core.
100 grains of Pyrodex or Triple 7 with any well constructed 250-300 gr bullet will kill any deer we have in Ohio.
Powerbelts have a following of hunters that love them and an even larger group of hunters that strongly dislike them. The only attribute they really have is that they load easily.
You may want to try some Blackhorn 209, Burns a little hotter and MUCH cleaner that the other black powder substitutes.
If you are new to muzzleloading just make sure you have a witness mark on your ram rod and ensure that you have your load fully seated and that you have not double loaded PRIOR to ever pulling the trigger.
Hope you get a big one.