Yes the rifle will handle 150 grains of pellets, but no loose powder. There really is little need to shoot pellets or 150 grains of pellets as loose powder works just as well or better.

100 grains is normally a good deer load. Although if you're shooting such a light bullet you might want to try 80 grains and see what kind of accuracy you can shoot.

If you want to shoot long range you might look into the Barnes Expanders, Shockwaves, Nosler, Speer Gold Dots, or Parker Extreme. They can take a little more powder.

Also that rifle can shoot Black Horn 209 powder. But Pyrodex RS, Triple Se7en, will work well.