Barnes ML bullets are deadly on deer I harvested six with them last year, as for the powder charge I would start at 100grains of loose powder and shoot a three round group, then go up 10 grains at a time until the grouping of your bullets starts to open up. At this point you need to stop.
If you go with pelltes it's easier, but you have less options in tuning your muzzleloader due to the size of the pellets, either will work it just depends on how picky you are about accuracy.
Good luck