Ernie,
The best powder I have found for the 180 gr. bullet in the 7MMWSM is reloader #25, start with 65 grs and I worked my way up to 67.5 gr with no pressure signs. Muzzle velocity out of a 30" Krieger is 3,150 fps and accuracy is awesome
Hogdon retumbo would also be a good one but in my experiance, which is not that extensive retumbo did not like to be a compressed load as velocity spread increased drasticlly once the bullet started to compress the powder.
FWIW,
308nate