You might want to drop your powder charge. Just because the rifle will shoot 150 grains of powder does not mean that is where your best accuracy will be. My T/C Black Diamond XR is a magnum rifle also, but the charges between 100-120 grains are the most accurate. Back it off to 100 grains and see what happens. That is still plenty of power to taken anything you want to shoot at.

I have never shot the Barnes but have read some excellent reviews on them. Another good bullet to try is the Hornady SST and the XTP. I have good luck shooting them.

Good luck.