Since my 300 WSM showed pressure signs at 67 grains of W760 and the 165 grain bullet,
I would start a bit lower than 66 grains with the 180.
Yours may be fine with 66 gr or even more with the 180, but to be safe, I would start lower.
FWIW, my 300 WSM really likes W760 and the 165 grain bullet.
With the 180, I have been using Norma MRP with great success. [Reloder 22 should give similar results.]
Cheers, Dave.