Its the magnum, that is a very tuff bullet, I doubt its opening properly with only 100 grains of Pyrodex.
If you drill a neat round hole through deer even through both lungs and its a well placed shot they will run a long way.
The velocity also could be improved, I suggest you look at the 250 grain Shock Wave or the 250 grain Deep curl and try their accuracy with 110 to 130 grains of Pyrodex and use the most accurate load. Forget the 150 grain load as it is only accurate out of a few guns and therefor try it after all else fails.