I've never shot pellets out of my rifle and never shot 150 grains yet. 100 grains of Pyrodex P is about all the power I would need unless I headed to Africa. Jim Shockey for years (I read) shot 100 grains of Pyrodex RS and used a Nosler Partition bullet and took everything from mice to moose with that load.

If you want to shoot long range, I am not saying a powerbelt can not do it, because I never tried, but I would think there are better projectiles out there for that then a powerbelt. Although FG does some impressive shooting with them and he normally shoots 80 grains of powder with them.