There are many variables but the most obvious problem in what you said is a magnum bullet with your load, going to 150 grain is not often a good answer as most guns loose accuracy before you get that far.
I would recommend going up 10 grains at a time until your groups tell you to back off.
As far as that bullet is concerned I did some testing on it and followed some tests other people did and decided not to use it. You might try Lehigh or barns or even XTP for better results