Welcome to the forum

If I were you and you are set on the Power belts I would drop my powder down to 80 or 85gr
Just me I do not like the BP I would rather shoot the Bull Shop Custom CONICALS they are alot cheaper than the PB , I shoot a 460gr NEX bull shop in a .504 with with a .510 over the powder wad and 85gr of loose 2gf 777 out of my KRB7 and you talk about ACCURATE . just orderd 400 of them with shipping was $113.50 the wads you can get 1000 for 7.50 .
I just had some Bad exper. with the BP and swore I would never use them again but like I said it is (JMO)
If I was going to shoot the BP I would shoot the 338gr platinum over 85 or 90gr of powder.

www.bullshop.gunloads.com